Noticing that the equation with double-Poisson bracket, where On is normal coordinate, Hc is classical Hamiltonian, is the classical correspondence of the invariant eigen-operator equation （2004 Phys. Left. A. 321 75...Noticing that the equation with double-Poisson bracket, where On is normal coordinate, Hc is classical Hamiltonian, is the classical correspondence of the invariant eigen-operator equation （2004 Phys. Left. A. 321 75）, we can find normal coordinates in harmonic crystal by virtue of the invaxiant eigen-operator method.展开更多
In this paper, we provide a new kind of operator formula for anti-normally and normally ordering bosonic-operator functions in quantum optics, which can help us arrange a bosonic-operator function f（λQ ＋ VP） in it...In this paper, we provide a new kind of operator formula for anti-normally and normally ordering bosonic-operator functions in quantum optics, which can help us arrange a bosonic-operator function f（λQ ＋ VP） in its anti-normal and normal ordering conveniently. Furthermore, mutual transformation formulas between anti-normal ordering and normal ordering, which have good universality, are derived too. Based on these operator formulas, some new differential relations and some useful mathematical integral formulas are easily derived without really performing these integrations.展开更多
By extending the usual Wigner operator to the s−parameterized one,we find that in the process of the generalized Weyl quantization the s parameter plays the role of correlation between two quadratures Q and P.This can...By extending the usual Wigner operator to the s−parameterized one,we find that in the process of the generalized Weyl quantization the s parameter plays the role of correlation between two quadratures Q and P.This can be exposed by comparing the normally ordered form ofΩs with the standard form of the Gaussian bivariate normal distribution of random variables in statistics.Three different expressions ofΩs and the quantization scheme with use of it are presented.展开更多
Sodium with low cost and high abundance is considered as a substitute element of lithium for batteries and supercapacitors,which need the appropriate host materials to accommodate the relatively large Na^(+) ions.Comp...Sodium with low cost and high abundance is considered as a substitute element of lithium for batteries and supercapacitors,which need the appropriate host materials to accommodate the relatively large Na^(+) ions.Compared to Li^(+) storage,Na^(+) storage makes higher demands on the structural optimization of perovskite bismuth ferrite(BiFeO_(3)).We propose a novel strategy of defect engineering on BiFeO_(3) through Na and V codoping for high-efficiency Na^(+) storage,to reveal the roles of oxygen vacancies and V ions played in the enhanced electrochemical energy storage performances of Na-ion capacitors.The formation of the oxygen vacancies in the Na and V codoped BiFeO_(3)(denoted as NV-BFO),is promoted by Na doping and suppressed by V doping,which can be demonstrated by XPS and EPR spectra.By the first-principles calculations,the oxygen vacancies and V ions in NV-BFO are confirmed to substantially lower the Na^(+)migration energy barriers through the space and electric field effects,to effectively promote the Na^(+) transport in the crystals.Electrochemical kinetic analysis of the NV-BFO//NV-BFO capacitors indicates the dominant capacitive-controlled capacity,which depends on fast Na^(+) deintercalation-intercalation process in the NV-BFO electrode.The NV-BFO//NV-BFO capacitors open up a new avenue for developing highperformance Na-ion capacitors.展开更多
High-performance quantum anomalous Hall(QAH)systems are crucial materials for exploring emerging quantum physics and magnetic topological phenomena.Inspired by layered FeSe materials with excellent superconducting pro...High-performance quantum anomalous Hall(QAH)systems are crucial materials for exploring emerging quantum physics and magnetic topological phenomena.Inspired by layered FeSe materials with excellent superconducting properties,the Janus monolayers Fe_(2)SSeX_(2)(X=Ga,In and Tl)are built by the decoration of Ga,In and T1 atoms in monolayer Fe_(2)SSe.In first-principles calculations,Fe_(2)SSeX_(2)have stable structures and prefer ferromagnetic(FM)ordering,and can be considered as Weyl semimetals without spin-orbit coupling.For out-of-plane(OOP)magnetic anisotropy,large nontrivial gaps are opened and the Fe_(2)SSeX_(2)are predicted to be large-gap QAH insulators with a high Chern number C=2,proved by two chiral edge states and Berry curvature.When the magnetization is flipped,the two chiral edge states can be simultaneously changed and C=-2 can be obtained,revealing the fascinating behavior of chiral spin-edge state locking.It is found that the QAH properties of Fe_(2)SSeX_(2)are robust against strain.In particular,nontrivial topological quantum states can spontaneously appear for Fe_(2)SSeGa_(2)and Fe_(2)SSeIn_(2)because the orientations of the easy magnetic axis are adjusted from in-plane to OOP by the biaxial strain.Our studies provide excellent candidate systems to realize QAH properties with a high Chern number,and suggest more experimental explorations combining superconductivity and topology.展开更多
Valley-polarized quantum anomalous Hall effect(VQAHE), combined nontrivial band topology with valleytronics,is of importance for both fundamental sciences and emerging applications. However, the experimental realizati...Valley-polarized quantum anomalous Hall effect(VQAHE), combined nontrivial band topology with valleytronics,is of importance for both fundamental sciences and emerging applications. However, the experimental realization of this property is challenging. Here, by using first-principles calculations and modal analysis, we predict a mechanism of producing VQAHE in two-dimensional ferromagnetic van der Waals germanene/MnI_(2) heterostructure. This heterostructure exhibits both valley anomalous Hall effect and VQAHE due to the joint effects of magnetic exchange effect and spin–orbital coupling with the aid of anomalous Hall conductance and chiral edge state. Moreover interestingly, through the electrical modulation of ferroelectric polarization state in In_(2)Se_(3), the germanene/Mn I_(2)/In_(2)Se_(3) heterostructure can undergo reversible switching from a semiconductor to a metallic behavior. This work offers a guiding advancement for searching for VQAHE in ferromagnetic van der Waals heterostructures and exploiting energy-efficient devices based on the VQAHE.展开更多
A new kind of non-Gaussian quantum catalyzed state is proposed via multiphoton measurements and two-mode squeezing as an input of thermal state.The characteristics of the generated multiphoton catalysis output state d...A new kind of non-Gaussian quantum catalyzed state is proposed via multiphoton measurements and two-mode squeezing as an input of thermal state.The characteristics of the generated multiphoton catalysis output state depends on the thermal parameter,catalyzed photon number and squeezing parameter.We then analyze the nonclassical properties by examining the photon number distribution,photocount distribution and partial negativity of the Wigner function.Our findings indicate that nonclassicality can be achieved through the implementation of multiphoton catalysis operations and modulated by the thermal parameter,catalyzed photon number and squeezing parameter.展开更多
As a sister compound of PbTe, SnTe possesses the environmentally friendly elements. However, the pristine SnTe compounds suffer from the high carrier concentration, the large valence band offset between the L and Σpo...As a sister compound of PbTe, SnTe possesses the environmentally friendly elements. However, the pristine SnTe compounds suffer from the high carrier concentration, the large valence band offset between the L and Σpositions and high thermal conductivity. Using high-pressure and high-temperature technology, we synthesized the pristine SnTe samples at different pressures and systemically investigated their thermoelectric properties.High pressure induces rich microstructures, including the high-density dislocations and lattice distortions, which serve as the strong phonon scattering centers, thereby reducing the lattice thermal conductivity. For the electrical properties, pressure reduces the harmful high carrier concentration, due to the depression of Sn vacancies.Moreover, pressure induces the valence band convergence, reducing the energy separation between the L and Σpositions. The band convergence and suppressed carrier concentration increase the Seebeck coefficient. Thus, the power factors of pressure-sintered compounds do not deteriorate significantly under the condition of decreasing electrical conductivity. Ultimately, for a pristine SnTe compound synthesized at 5 GPa, a higher ZT value of 0.51 is achieved at 750 K, representing a 140% improvement compared to the value of 0.21 obtained using SPS. Therefore, the high-pressure and high-temperature technology is demonstrated as an effectively approach to optimize thermoelectric performance.展开更多
This paper studies the non-homogeneous generalized Riemann-Hilbert(RH)problems involving two unknown functions.Using the uniformization theorem,such problems are transformed into the case of homogeneous type.By the th...This paper studies the non-homogeneous generalized Riemann-Hilbert(RH)problems involving two unknown functions.Using the uniformization theorem,such problems are transformed into the case of homogeneous type.By the theory of classical boundary value problems,we adopt a novel method to obtain the sectionally analytic solutions of problems in strip domains,and analyze the conditions of solvability and properties of solutions in various domains.展开更多
Betula platyphylla and Betula costata are important species in mixed broadleaved-Korean pine(Pinus koraiensis)forests.However,the specific ways in which their growth is affected by warm temperatures and drought remain...Betula platyphylla and Betula costata are important species in mixed broadleaved-Korean pine(Pinus koraiensis)forests.However,the specific ways in which their growth is affected by warm temperatures and drought remain unclear.To address this issue,60 and 62 tree-ring cores of B.platyphylla and B.costata were collected in Yichun,China.Using dendrochronological methods,the response and adaptation of these species to climate change were examined.A“hysteresis effect”was found in the rings of both species,linked to May–September moisture conditions of the previous year.Radial growth of B.costata was positively correlated with the standardized precipitation-evapotranspiration index(SPEI),the precipitation from September to October of the previous year,and the relative humidity in October of the previous year.Growth of B.costata is primarily restricted by moisture conditions from September to October.In contrast,B.platyphylla growth is mainly limited by minimum temperatures in May–June of both the previous and current years.After droughts,B.platyphylla had a faster recovery rate compared to B.costata.In the context of rising temperatures since 1980,the correlation between B.platyphylla growth and monthly SPEI became positive and strengthened over time,while the growth of B.costata showed no conspicuous change.Our findings suggest that the growth of B.platyphylla is already affected by warming temperatures,whereas B.costata may become limited if warming continues or intensifies.Climate change could disrupt the succession of these species,possibly accelerating the succession of pioneer species.The results of this research are of great significance for understanding how the growth changes of birch species under warming and drying conditions,and contribute to understanding the structural adaptation of mixed broadleaved-Korean pine(Pinus koraiensis)forests under climate change.展开更多
We investigate the electronic structure of NbGeSb with non-symmorphic symmetry.We employ angle-resolved photoemission spectroscopy(ARPES)to observe and identify the bulk and surface states over the Brillouin zone.By u...We investigate the electronic structure of NbGeSb with non-symmorphic symmetry.We employ angle-resolved photoemission spectroscopy(ARPES)to observe and identify the bulk and surface states over the Brillouin zone.By utilizing high-energy photons,we identify the bulk Fermi surface and bulk nodal line along the direction X–R,while the Fermi surface of the surface state is observed by using low-energy photons.We observe the splitting of surface bands away from the high-symmetry point X.The density functional theory calculations on bulk and 1 to 5-layer slab models,as well as spin textures of NbGeSb,verify that the band splitting could be attributed to the Rashba-like spin–orbit coupling caused by space-inversion-symmetry breaking at the surface.These splitted surface bands cross with each other,forming two-dimensional Weyl-like crossings that are protected by mirror symmetry.Our findings provide insights into the two-dimensional topological and symmetry-protected band inversion of surface states.展开更多
Based on first-principles calculations, we systematically study the stacking energy and interlayer magnetic interaction of the heterobilayer composed of CrI_(3) and CrSe_(2) monolayers. It is found that the stacking o...Based on first-principles calculations, we systematically study the stacking energy and interlayer magnetic interaction of the heterobilayer composed of CrI_(3) and CrSe_(2) monolayers. It is found that the stacking order plays a crucial role in the interlayer magnetic coupling. Among all possible stacking structures, the AA-stacking is the most stable heterostructure, exhibiting interlayer antiferromagnetic interactions. Interestingly, the interlayer magnetic interaction can be effectively tuned by biaxial strain. A 4.3% compressive strain would result in a ferromagnetic interlayer interaction in all stacking orders. These results reveal the magnetic properties of CrI_(3)/CrSe_(2) heterostructure, which is expected to be applied to spintronic devices.展开更多
In this paper,we introduce the notions of_((m,n))-coherent rings and FP_((m,n))-projective modules for nonnegative integers m,n.We prove that(FP_((m,n))-Proj,(FPn-id)_(≤m))is a complete cotorsion pair for any m,n≥0 ...In this paper,we introduce the notions of_((m,n))-coherent rings and FP_((m,n))-projective modules for nonnegative integers m,n.We prove that(FP_((m,n))-Proj,(FPn-id)_(≤m))is a complete cotorsion pair for any m,n≥0 and it is hereditary if and only if the ring R is a left n-coherent ring for all m≥0 and n≥1.Moreover,we study the existence of FP_((m,n))-Proj covers and envelopes and obtain that if FP_((m,n))-Proj is closed under pure quotients,then FP_((m,n))-Proj is covering for any n≥2.As applications,we obtain that every R-module has an epic FP_((m,n))-Proj-envelope if and only if the left FP_((m,n))-global dimension of R is at most 1 and FP_((m,n))-Proj is closed under direct products.展开更多
A controlled bidirectional quantum secret direct communication scheme is proposed by using a Greenberger- Horne-Zeilinger （GHZ） state. In the scheme, two users can exchange their secret messages simultaneously with ...A controlled bidirectional quantum secret direct communication scheme is proposed by using a Greenberger- Horne-Zeilinger （GHZ） state. In the scheme, two users can exchange their secret messages simultaneously with a set of devices under the control of a third party. The security of the scheme is analysed and confirmed.展开更多
Some doubly-periodic solutions of the Zakharov-Kuznetsov equation are presented. Our approach is to introduce an auxiliary ordinary differential equation and use its Jacobi elliptic function solutions to construct dou...Some doubly-periodic solutions of the Zakharov-Kuznetsov equation are presented. Our approach is to introduce an auxiliary ordinary differential equation and use its Jacobi elliptic function solutions to construct doubly-periodic solutions of the Zakharov-Kuznetsov equation, which has been derived by Gottwald as a two-dimensional model for nonlinear Rossby waves. When the modulus k →1, these solutions reduce to the solitary wave solutions of the equation.展开更多
Lithium–sulfur(Li–S)batteries have been recognized as promising substitutes for current energy-storage technologies owing to their exceptional advantages in very high-energy density and excellent material sustainabi...Lithium–sulfur(Li–S)batteries have been recognized as promising substitutes for current energy-storage technologies owing to their exceptional advantages in very high-energy density and excellent material sustainability.The cathode with high sulfur areal loading is vital for the practical applications of Li–S batteries with very high energy density.However,the high sulfur loading in an electrode results in poor rate and cycling performances of batteries in most cases.Herein,we used diameters of 5.0(D5)and 13.0(D13)mm to probe the effect of electrodes with different sizes on the rate and cycling performances under a high sulfur loading(4.5 mg cm^-2).The cell with D5 sulfur cathode exhibits better rate and cycling performances comparing with a large(D13)cathode.Both the high concentration of lithium polysulfides and corrosion of lithium metal anode impede rapid kinetics of sulfur redox reactions,which results in inferior battery performance of the Li–S cell with large diameter cathode.This work highlights the importance of rational matching of the large sulfur cathode with a high areal sulfur loading,carbon modified separators,organic electrolyte,and Li metal anode in a pouch cell,wherein the sulfur redox kinetics and lithium metal protection should be carefully considered under the flooded lithium polysulfide conditions in a working Li–S battery.展开更多
Using the well-behaved features of the thermal entangled state representation, we solve the diffusion master equation under the action of a linear resonance force, and then obtain the infinitive operator-sum represent...Using the well-behaved features of the thermal entangled state representation, we solve the diffusion master equation under the action of a linear resonance force, and then obtain the infinitive operator-sum representation of the density operator. This approach may also be effective for treating other master equations. Moreover, we find that the initial pure coherent state evolves into a mixed thermal state after passing through the diffusion process under the action of the linear resonance force.展开更多
Optical and electrical properties of diamond-like carbon （DLC） films deposited by pulsed laser ablation of graphite target at different substrate temperatures are reported. By varying the deposition temperature from...Optical and electrical properties of diamond-like carbon （DLC） films deposited by pulsed laser ablation of graphite target at different substrate temperatures are reported. By varying the deposition temperature from 400 to 25℃, the film optical transparency and electrical resistivity increase severely. Most importantly, the transparency and resistivity properties of the DLC films can be tailored to approaching diamond by adjusting the deposition temperature, which is critical to many applications. DLC films deposited at low temperatures show excellent optical transmittance and high resistivity. Over the same temperature regime an increase of the spa bonded C content is observed using visible Raman spectroscopy, which is responsible for the enhanced transparency and resistivity properties.展开更多
We investigate how displaced thermal states （DTSs） evolve in a laser channel. Remarkably, the initial DTS, an example of a mixed state, still remains mixed and thermal. At long times, they finally decay to a highly ...We investigate how displaced thermal states （DTSs） evolve in a laser channel. Remarkably, the initial DTS, an example of a mixed state, still remains mixed and thermal. At long times, they finally decay to a highly classical thermal field only related to the laser parameters κ and g. The normal ordering product of density operator of the DTS in the laser channel leads to obtaining the analytical time-evolution expressions of the photon number, Wigner function, and von Neumann entropy. Also, some interesting results are presented via numerically investigating these explicit time-dependent expressions.展开更多
The macroscopic quantum entanglement in capacitively coupled SQUID （superconducting quantum interference device）-based charge qubits is investigated theoretically. The entanglement characteristic is discussed by emp...The macroscopic quantum entanglement in capacitively coupled SQUID （superconducting quantum interference device）-based charge qubits is investigated theoretically. The entanglement characteristic is discussed by employing the quantum Rabi oscillations and the concurrence. An interesting conclusion is obtained, i.e., the magnetic fluxes φx1 and φx2 through the superconducting loops can adjust the entanglement degree between the qubits.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 10574060)the Natural Science Foundation of Shandong Province of China (Grant No. Y2008A23)the Shandong Province Higher Educational Science and Technology Program (Grant No. J09LA07)
文摘Noticing that the equation with double-Poisson bracket, where On is normal coordinate, Hc is classical Hamiltonian, is the classical correspondence of the invariant eigen-operator equation （2004 Phys. Left. A. 321 75）, we can find normal coordinates in harmonic crystal by virtue of the invaxiant eigen-operator method.
基金Project supported by the Natural Science Foundation of Shandong Province,China(Grant No.ZR2015AM025)the Natural Science Foundation of Heze University,China(Grant No.XY14PY02)
文摘In this paper, we provide a new kind of operator formula for anti-normally and normally ordering bosonic-operator functions in quantum optics, which can help us arrange a bosonic-operator function f（λQ ＋ VP） in its anti-normal and normal ordering conveniently. Furthermore, mutual transformation formulas between anti-normal ordering and normal ordering, which have good universality, are derived too. Based on these operator formulas, some new differential relations and some useful mathematical integral formulas are easily derived without really performing these integrations.
基金Supported by the National Natural Science Foundation of China under Grant No.10574060the Natural Science Foundation of Shandong Province under Grant No.ZR2010AQ027the Shandong Provincial Higher Educational Science and Technology Program under Grant Nos.J09LA07 and J10LA15.
文摘By extending the usual Wigner operator to the s−parameterized one,we find that in the process of the generalized Weyl quantization the s parameter plays the role of correlation between two quadratures Q and P.This can be exposed by comparing the normally ordered form ofΩs with the standard form of the Gaussian bivariate normal distribution of random variables in statistics.Three different expressions ofΩs and the quantization scheme with use of it are presented.
基金financial supports from National Natural Science Foundation of China(22005174 and 52271133)。
文摘Sodium with low cost and high abundance is considered as a substitute element of lithium for batteries and supercapacitors,which need the appropriate host materials to accommodate the relatively large Na^(+) ions.Compared to Li^(+) storage,Na^(+) storage makes higher demands on the structural optimization of perovskite bismuth ferrite(BiFeO_(3)).We propose a novel strategy of defect engineering on BiFeO_(3) through Na and V codoping for high-efficiency Na^(+) storage,to reveal the roles of oxygen vacancies and V ions played in the enhanced electrochemical energy storage performances of Na-ion capacitors.The formation of the oxygen vacancies in the Na and V codoped BiFeO_(3)(denoted as NV-BFO),is promoted by Na doping and suppressed by V doping,which can be demonstrated by XPS and EPR spectra.By the first-principles calculations,the oxygen vacancies and V ions in NV-BFO are confirmed to substantially lower the Na^(+)migration energy barriers through the space and electric field effects,to effectively promote the Na^(+) transport in the crystals.Electrochemical kinetic analysis of the NV-BFO//NV-BFO capacitors indicates the dominant capacitive-controlled capacity,which depends on fast Na^(+) deintercalation-intercalation process in the NV-BFO electrode.The NV-BFO//NV-BFO capacitors open up a new avenue for developing highperformance Na-ion capacitors.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.52173283 and 62071200)Taishan Scholar Program of Shandong Province(Grant No.ts20190939)Independent Cultivation Program of Innovation Team of Jinan City(Grant No.2021GXRC043)。
文摘High-performance quantum anomalous Hall(QAH)systems are crucial materials for exploring emerging quantum physics and magnetic topological phenomena.Inspired by layered FeSe materials with excellent superconducting properties,the Janus monolayers Fe_(2)SSeX_(2)(X=Ga,In and Tl)are built by the decoration of Ga,In and T1 atoms in monolayer Fe_(2)SSe.In first-principles calculations,Fe_(2)SSeX_(2)have stable structures and prefer ferromagnetic(FM)ordering,and can be considered as Weyl semimetals without spin-orbit coupling.For out-of-plane(OOP)magnetic anisotropy,large nontrivial gaps are opened and the Fe_(2)SSeX_(2)are predicted to be large-gap QAH insulators with a high Chern number C=2,proved by two chiral edge states and Berry curvature.When the magnetization is flipped,the two chiral edge states can be simultaneously changed and C=-2 can be obtained,revealing the fascinating behavior of chiral spin-edge state locking.It is found that the QAH properties of Fe_(2)SSeX_(2)are robust against strain.In particular,nontrivial topological quantum states can spontaneously appear for Fe_(2)SSeGa_(2)and Fe_(2)SSeIn_(2)because the orientations of the easy magnetic axis are adjusted from in-plane to OOP by the biaxial strain.Our studies provide excellent candidate systems to realize QAH properties with a high Chern number,and suggest more experimental explorations combining superconductivity and topology.
基金Project supported by the National Natural Science Foundation of China (Grant No. 52173283)Taishan Scholar Program of Shandong Province (Grant No. ts20190939)Independent Cultivation Program of Innovation Team of Jinan City (Grant No. 2021GXRC043)。
文摘Valley-polarized quantum anomalous Hall effect(VQAHE), combined nontrivial band topology with valleytronics,is of importance for both fundamental sciences and emerging applications. However, the experimental realization of this property is challenging. Here, by using first-principles calculations and modal analysis, we predict a mechanism of producing VQAHE in two-dimensional ferromagnetic van der Waals germanene/MnI_(2) heterostructure. This heterostructure exhibits both valley anomalous Hall effect and VQAHE due to the joint effects of magnetic exchange effect and spin–orbital coupling with the aid of anomalous Hall conductance and chiral edge state. Moreover interestingly, through the electrical modulation of ferroelectric polarization state in In_(2)Se_(3), the germanene/Mn I_(2)/In_(2)Se_(3) heterostructure can undergo reversible switching from a semiconductor to a metallic behavior. This work offers a guiding advancement for searching for VQAHE in ferromagnetic van der Waals heterostructures and exploiting energy-efficient devices based on the VQAHE.
基金supported by the National Natural Science Foundation of China (Grant No.11347026)the Natural Science Foundation of Shandong Province,China (Grant Nos.ZR2020MA085 and ZR2020MF113)。
文摘A new kind of non-Gaussian quantum catalyzed state is proposed via multiphoton measurements and two-mode squeezing as an input of thermal state.The characteristics of the generated multiphoton catalysis output state depends on the thermal parameter,catalyzed photon number and squeezing parameter.We then analyze the nonclassical properties by examining the photon number distribution,photocount distribution and partial negativity of the Wigner function.Our findings indicate that nonclassicality can be achieved through the implementation of multiphoton catalysis operations and modulated by the thermal parameter,catalyzed photon number and squeezing parameter.
基金supported by the National Natural Science Foundation of China (Grant Nos. 12374012, 11974208, 52172212, and 52002217)Shandong Provincial Natural Science Foundation (Grant Nos. ZR2023JQ001, ZR2020YQ05, and 2019KJJ020)financial support from the Program of Distinguished Expert of Taishan Scholar (Grant No. tstp20221124)。
文摘As a sister compound of PbTe, SnTe possesses the environmentally friendly elements. However, the pristine SnTe compounds suffer from the high carrier concentration, the large valence band offset between the L and Σpositions and high thermal conductivity. Using high-pressure and high-temperature technology, we synthesized the pristine SnTe samples at different pressures and systemically investigated their thermoelectric properties.High pressure induces rich microstructures, including the high-density dislocations and lattice distortions, which serve as the strong phonon scattering centers, thereby reducing the lattice thermal conductivity. For the electrical properties, pressure reduces the harmful high carrier concentration, due to the depression of Sn vacancies.Moreover, pressure induces the valence band convergence, reducing the energy separation between the L and Σpositions. The band convergence and suppressed carrier concentration increase the Seebeck coefficient. Thus, the power factors of pressure-sintered compounds do not deteriorate significantly under the condition of decreasing electrical conductivity. Ultimately, for a pristine SnTe compound synthesized at 5 GPa, a higher ZT value of 0.51 is achieved at 750 K, representing a 140% improvement compared to the value of 0.21 obtained using SPS. Therefore, the high-pressure and high-temperature technology is demonstrated as an effectively approach to optimize thermoelectric performance.
基金Supported by National Natural Science Foundation of China(Grant No.11971015).
文摘This paper studies the non-homogeneous generalized Riemann-Hilbert(RH)problems involving two unknown functions.Using the uniformization theorem,such problems are transformed into the case of homogeneous type.By the theory of classical boundary value problems,we adopt a novel method to obtain the sectionally analytic solutions of problems in strip domains,and analyze the conditions of solvability and properties of solutions in various domains.
基金the Key Project of the China National Key Research and Development Program(2021YFD2200401)the National Natural Science Foundation of China(42177421 and 41877426)。
文摘Betula platyphylla and Betula costata are important species in mixed broadleaved-Korean pine(Pinus koraiensis)forests.However,the specific ways in which their growth is affected by warm temperatures and drought remain unclear.To address this issue,60 and 62 tree-ring cores of B.platyphylla and B.costata were collected in Yichun,China.Using dendrochronological methods,the response and adaptation of these species to climate change were examined.A“hysteresis effect”was found in the rings of both species,linked to May–September moisture conditions of the previous year.Radial growth of B.costata was positively correlated with the standardized precipitation-evapotranspiration index(SPEI),the precipitation from September to October of the previous year,and the relative humidity in October of the previous year.Growth of B.costata is primarily restricted by moisture conditions from September to October.In contrast,B.platyphylla growth is mainly limited by minimum temperatures in May–June of both the previous and current years.After droughts,B.platyphylla had a faster recovery rate compared to B.costata.In the context of rising temperatures since 1980,the correlation between B.platyphylla growth and monthly SPEI became positive and strengthened over time,while the growth of B.costata showed no conspicuous change.Our findings suggest that the growth of B.platyphylla is already affected by warming temperatures,whereas B.costata may become limited if warming continues or intensifies.Climate change could disrupt the succession of these species,possibly accelerating the succession of pioneer species.The results of this research are of great significance for understanding how the growth changes of birch species under warming and drying conditions,and contribute to understanding the structural adaptation of mixed broadleaved-Korean pine(Pinus koraiensis)forests under climate change.
基金Project supported by the National Key Research and Development Program of China(Grant No.2022YFA1403803)H.M.is supported by the Fundamental Research Funds for the Central Universities,and the Research Funds of Renmin University of China(Grant No.22XNH099)+7 种基金The results of DFT calculations described in this paper are supported by HPC Cluster of ITP-CAS.M.L.is supported by the National Natural Science Foundation of China(Grant No.12204536)the Fundamental Research Funds for the Central Universities,and the Research Funds of People’s Public Security University of China(PPSUC)(Grant No.2023JKF02ZK09)T.L.X.is supported by the National Key R&D Program of China(Grant No.2019YFA0308602)the National Natural Science Foundation of China(Grant Nos.12074425 and 11874422)Y.Y.W.is supported by the National Natural Science Foundation of China(Grant No.12104011)H.Y.L.is supported by the National Natural Science Foundation of China(Grant No.12074213)the Major Basic Program of Natural Science Foundation of Shandong Province(Grant No.ZR2021ZD01)the Project of Introduction and Cultivation for Young Innovative Talents in Colleges and Universities of Shandong Province.
文摘We investigate the electronic structure of NbGeSb with non-symmorphic symmetry.We employ angle-resolved photoemission spectroscopy(ARPES)to observe and identify the bulk and surface states over the Brillouin zone.By utilizing high-energy photons,we identify the bulk Fermi surface and bulk nodal line along the direction X–R,while the Fermi surface of the surface state is observed by using low-energy photons.We observe the splitting of surface bands away from the high-symmetry point X.The density functional theory calculations on bulk and 1 to 5-layer slab models,as well as spin textures of NbGeSb,verify that the band splitting could be attributed to the Rashba-like spin–orbit coupling caused by space-inversion-symmetry breaking at the surface.These splitted surface bands cross with each other,forming two-dimensional Weyl-like crossings that are protected by mirror symmetry.Our findings provide insights into the two-dimensional topological and symmetry-protected band inversion of surface states.
基金supported by the National Natural Science Foundation of China (Grant Nos. 12074213, 11574108, 12104253, 12104034, 12022415, and 12374054)the Major Basic Program of Natural Science Foundation of Shandong Province (Grant No. ZR2021ZD01)the Project of Introduction and Cultivation for Young Innovative Talents in Colleges and Universities of Shandong Province。
文摘Based on first-principles calculations, we systematically study the stacking energy and interlayer magnetic interaction of the heterobilayer composed of CrI_(3) and CrSe_(2) monolayers. It is found that the stacking order plays a crucial role in the interlayer magnetic coupling. Among all possible stacking structures, the AA-stacking is the most stable heterostructure, exhibiting interlayer antiferromagnetic interactions. Interestingly, the interlayer magnetic interaction can be effectively tuned by biaxial strain. A 4.3% compressive strain would result in a ferromagnetic interlayer interaction in all stacking orders. These results reveal the magnetic properties of CrI_(3)/CrSe_(2) heterostructure, which is expected to be applied to spintronic devices.
基金supported by the National Natural Science Foundation of China(No.12471036),the project of Young and Middle-Aged Talents of Hubei Province(No.Q20234405),and the Scientific Research Fund of Hunan Provincial Education Department(No.24A0221)。
文摘In this paper,we introduce the notions of_((m,n))-coherent rings and FP_((m,n))-projective modules for nonnegative integers m,n.We prove that(FP_((m,n))-Proj,(FPn-id)_(≤m))is a complete cotorsion pair for any m,n≥0 and it is hereditary if and only if the ring R is a left n-coherent ring for all m≥0 and n≥1.Moreover,we study the existence of FP_((m,n))-Proj covers and envelopes and obtain that if FP_((m,n))-Proj is closed under pure quotients,then FP_((m,n))-Proj is covering for any n≥2.As applications,we obtain that every R-module has an epic FP_((m,n))-Proj-envelope if and only if the left FP_((m,n))-global dimension of R is at most 1 and FP_((m,n))-Proj is closed under direct products.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10534030 and 10304022.
文摘A controlled bidirectional quantum secret direct communication scheme is proposed by using a Greenberger- Horne-Zeilinger （GHZ） state. In the scheme, two users can exchange their secret messages simultaneously with a set of devices under the control of a third party. The security of the scheme is analysed and confirmed.
文摘Some doubly-periodic solutions of the Zakharov-Kuznetsov equation are presented. Our approach is to introduce an auxiliary ordinary differential equation and use its Jacobi elliptic function solutions to construct doubly-periodic solutions of the Zakharov-Kuznetsov equation, which has been derived by Gottwald as a two-dimensional model for nonlinear Rossby waves. When the modulus k →1, these solutions reduce to the solitary wave solutions of the equation.
基金supported by the National Key Research and Development Program(2016YFA0202500 and 2016YFA0200102)the National Natural Science Foundation of China(21776019,21805162,51772069,and U1801257)+1 种基金China Postdoctoral Science Foundation(2018M630165)Beijing Key Research and Development Plan(Z181100004518001)
文摘Lithium–sulfur(Li–S)batteries have been recognized as promising substitutes for current energy-storage technologies owing to their exceptional advantages in very high-energy density and excellent material sustainability.The cathode with high sulfur areal loading is vital for the practical applications of Li–S batteries with very high energy density.However,the high sulfur loading in an electrode results in poor rate and cycling performances of batteries in most cases.Herein,we used diameters of 5.0(D5)and 13.0(D13)mm to probe the effect of electrodes with different sizes on the rate and cycling performances under a high sulfur loading(4.5 mg cm^-2).The cell with D5 sulfur cathode exhibits better rate and cycling performances comparing with a large(D13)cathode.Both the high concentration of lithium polysulfides and corrosion of lithium metal anode impede rapid kinetics of sulfur redox reactions,which results in inferior battery performance of the Li–S cell with large diameter cathode.This work highlights the importance of rational matching of the large sulfur cathode with a high areal sulfur loading,carbon modified separators,organic electrolyte,and Li metal anode in a pouch cell,wherein the sulfur redox kinetics and lithium metal protection should be carefully considered under the flooded lithium polysulfide conditions in a working Li–S battery.
基金supported by the National Natural Science Foundation of China(Grant Nos.11347026,11147009,and 11244005)the Natural Science Foundation of Shandong Province,China(Grant Nos.ZR2013AM012 and ZR2012AM004)the Scientific Research Project of Liaocheng,China
文摘Using the well-behaved features of the thermal entangled state representation, we solve the diffusion master equation under the action of a linear resonance force, and then obtain the infinitive operator-sum representation of the density operator. This approach may also be effective for treating other master equations. Moreover, we find that the initial pure coherent state evolves into a mixed thermal state after passing through the diffusion process under the action of the linear resonance force.
基金Supported by the Natural Science Foundation of Shandong Province under Grant to No Y2002A09.
文摘Optical and electrical properties of diamond-like carbon （DLC） films deposited by pulsed laser ablation of graphite target at different substrate temperatures are reported. By varying the deposition temperature from 400 to 25℃, the film optical transparency and electrical resistivity increase severely. Most importantly, the transparency and resistivity properties of the DLC films can be tailored to approaching diamond by adjusting the deposition temperature, which is critical to many applications. DLC films deposited at low temperatures show excellent optical transmittance and high resistivity. Over the same temperature regime an increase of the spa bonded C content is observed using visible Raman spectroscopy, which is responsible for the enhanced transparency and resistivity properties.
基金Project supported by the National Natural Science Foundation of China(Grant No.11347026)the Natural Science Foundation of Shandong Province,China(Grant Nos.ZR2016AM03 and ZR2017MA011)
文摘We investigate how displaced thermal states （DTSs） evolve in a laser channel. Remarkably, the initial DTS, an example of a mixed state, still remains mixed and thermal. At long times, they finally decay to a highly classical thermal field only related to the laser parameters κ and g. The normal ordering product of density operator of the DTS in the laser channel leads to obtaining the analytical time-evolution expressions of the photon number, Wigner function, and von Neumann entropy. Also, some interesting results are presented via numerically investigating these explicit time-dependent expressions.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10574060)the Natural Science Foundation of Shandong Province, China (Grant No. Y2008A23)Project of Shandong Province Higher Educational Science and Technology Program (Grant No. J09LA07)
文摘The macroscopic quantum entanglement in capacitively coupled SQUID （superconducting quantum interference device）-based charge qubits is investigated theoretically. The entanglement characteristic is discussed by employing the quantum Rabi oscillations and the concurrence. An interesting conclusion is obtained, i.e., the magnetic fluxes φx1 and φx2 through the superconducting loops can adjust the entanglement degree between the qubits.
