Epitaxial graphene grown on silicon carbide(Si C/graphene)is a promising solution for achieving a highprecision quantum Hall resistance standard.Previous research mainly focused on the quantum resistance metrology of ...Epitaxial graphene grown on silicon carbide(Si C/graphene)is a promising solution for achieving a highprecision quantum Hall resistance standard.Previous research mainly focused on the quantum resistance metrology of n-type Si C/graphene,while a comprehensive understanding of the quantum resistance metrology behavior of graphene with different doping types is lacking.Here,we fabricated both n-and p-type Si C/graphene devices via polymer-assisted molecular adsorption and conducted systematic magneto-transport measurements in a wide parameter space of carrier density and temperature.It is demonstrated that n-type devices show greater potential for development of quantum resistance metrology compared with p-type devices,as evidenced by their higher carrier mobility,lower critical magnetic field for entering quantized Hall plateaus,and higher robustness of the quantum Hall effect against thermal degeneration.These discrepancies can be reasonably attributed to the weaker scattering from molecular dopants for n-type devices,which is further supported by the analyses on the quantum interference effect in multiple devices.These results enrich our understanding of the charged impurity on electronic transport performance of graphene and,more importantly,provide a useful reference for future development of graphene-based quantum resistance metrology.展开更多
A machine learning(ML)potential for Au clusters is developed through training on a dataset including several different sized clusters.This ML potential accurately covers the whole configuration space of Au clusters in...A machine learning(ML)potential for Au clusters is developed through training on a dataset including several different sized clusters.This ML potential accurately covers the whole configuration space of Au clusters in a broad size range,thus expressing a good performance in search of their global minimum energy structures.Based on our potential,the low-lying structures of 17 different sized Au clusters are identified,which shows that small sized Au clusters tend to form planar structures while large ones are more likely to be stereo,revealing the critical size for the two-dimensional(2D)to three-dimensional(3D)structural transition.Our calculations demonstrate that ML is indeed powerful in describing the interaction of Au atoms and provides a new paradigm on accelerating the search of structures.展开更多
For conductors in the ballistic regime, electron-boundary scattering at the sample edge plays a dominant role in determining the transport performance, giving rise to many intriguing phenomena like low-field negative ...For conductors in the ballistic regime, electron-boundary scattering at the sample edge plays a dominant role in determining the transport performance, giving rise to many intriguing phenomena like low-field negative magnetoresistance effect. We systematically investigate the magneto-transport behaviors of BN-encapsulated graphene devices with narrow channel width W, wherein the bulk mean free path Lmfp can be very large and highly tunable. By comparing the magnetoresistance features and the amplitude of Lmfp in a large parameter space of temperature and carrier density, we reveal that the boundary-scattering-dominated negative magnetoresistance effect can still survive even when the ballistic ratio(Lmfp/W) is as low as 0.15. This striking value is much smaller than the expected value for achieving(quasi-) ballistic transport regime(Lmfp/W ≥ 1), and can be attributed to the ultra-low specularity of the sample edge of our graphene devices. These findings enrich our understanding of the effects of boundary scattering on channel transport, which is of vital importance for future designs of two-dimensional electronic devices with limited lateral sizes.展开更多
Based on first-principles calculations,a two-dimensional(2D)van der Waals(vd W)bilayer heterostructure consisting of two topologically trivial ferromagnetic(FM)monolayers CrI_(3)and ScCl_(2)is proposed to realize the ...Based on first-principles calculations,a two-dimensional(2D)van der Waals(vd W)bilayer heterostructure consisting of two topologically trivial ferromagnetic(FM)monolayers CrI_(3)and ScCl_(2)is proposed to realize the quantum anomalous Hall effect(QAHE)with a sizable topologically nontrivial band gap of 4.5 me V.Its topological nature is attributed to an interlayer band inversion between the monolayers and critically depends on the symmetry of the stacking configuration.We further demonstrate that the topologically nontrivial band gap can be increased nearly linearly by the application of a perpendicular external pressure and reaches 8.1 me V at 2.7 GPa,and the application of an external out-of-plane electric field can also modulate the band gap and convert the system back to topologically trivial via eliminating the band inversion.An effective model is developed to describe the topological phase evolution in this bilayer heterostructure.This work provides a new candidate system based on 2D vd W materials for realization of potential high-temperature QAHE with considerable controllability.展开更多
Novel two-dimensional thermoelectric materials have attracted significant attention in the field of thermoelectric due to their low lattice thermal conductivity.A comprehensive understanding of their microscopic struc...Novel two-dimensional thermoelectric materials have attracted significant attention in the field of thermoelectric due to their low lattice thermal conductivity.A comprehensive understanding of their microscopic structures is crucial for driving further the optimization of materials properties and developing novel functional materials.Here,by using in situ scanning tunneling microscopy,we report the atomic layer evolution and surface reconstruction on the cleaved thermoelectric material KCu_(4)Se_(3) for the first time.We clearly revealed each atomic layer,including the naturally cleaved K atomic layer,the intermediate Se^(2-)atomic layer,and the Se^(-)atomic layer that emerges in the thermodynamic-stable state.Departing from the maj ority of studies that predominantly concentrate on macroscopic measurements of the charge transport,our results reveal the coexistence of potassium disorder and complex reconstructed patterns of selenium,which potentially influences charge carrier and lattice dynamics.These results provide direct insight into the surface microstructures and evolution of KCu_(4)Se_(3),and shed useful light on designing functional materials with superior performance.展开更多
Monolayer transition metal dichalcogenides can normally exist in several structural polymorphs with distinct electrical,optical,and catalytic properties.Effective control of the relative stability and transformation o...Monolayer transition metal dichalcogenides can normally exist in several structural polymorphs with distinct electrical,optical,and catalytic properties.Effective control of the relative stability and transformation of different phases in these materials is thus of critical importance for applications.Using density functional theory calculations,we investigate the effects of low-work-function metal substrates including Ti,Zr,and Hf on the structural,electronic,and catalytic properties of monolayer MoS_(2) and WS_(2).The results indicate that such substrates not only convert the energetically stable structure from the 1H phase to the 1T'/1T phase,but also significantly reduce the kinetic barriers of the phase transformation.Furthermore,our calculations also indicate that the 1T' phase of MoS_(2) with Zr or Hf substrate is a potential catalyst for the hydrogen evolution reaction.展开更多
Hybrid structures of two distinct materials provide an excellent opportunity to optimize functionalities.We report the realization of wide quantum Hall plateaus in graphene field-effect devices on the LaAlO3/SrTiO3 he...Hybrid structures of two distinct materials provide an excellent opportunity to optimize functionalities.We report the realization of wide quantum Hall plateaus in graphene field-effect devices on the LaAlO3/SrTiO3 heterostructures.Well-defined quantized Hall resistance plateaus at filling factors ν=±2 can be obtained over wide ranges of the magnetic field and gate voltage,e.g.,extending from 2 T to a maximum available magnetic field of 9 T.By using a simple band diagram model,it is revealed that these wide plateaus arise from the ultralarge capacitance of the ultra-thin LAO layer acting as the dielectric layer.This is distinctly different from the case of epitaxial graphene on Si C substrates,where the realization of giant Hall plateaus relies on the charge transfer between the graphene layer and interface states in SiC.Our results offer an alternative route towards optimizing the quantum Hall performance of graphene,which may find its applications in the further development of quantum resistance metrology.展开更多
Nanoclusters consisting of a few atoms have attracted a lot of research interests due to their exotic size-dependent properties. Here, well-ordered two-dimensional Sb cluster superlattice was fabricated on Si substrat...Nanoclusters consisting of a few atoms have attracted a lot of research interests due to their exotic size-dependent properties. Here, well-ordered two-dimensional Sb cluster superlattice was fabricated on Si substrate by a two-step method and characterized by scanning tunneling microscopy. High resolution scanning tunneling microscope measurements revealed the fine structures of the Sb clusters, which consist of several Sb atoms ranging from 2 to 7. Furthermore, the electronic structure of the nanocluster displays the quantized energy-level which is due to the single-electron tunneling effects. We believe that the fabrication of Sb cluster superlattice broadens the species of the cluster superlattice and provides a promising candidate to further explore the novel physical and chemical properties of the semimetal nanocluster.展开更多
Topological insulators （Tls） are bulk insulators that possess robust helical conducting states along their interfaces with conventional insulators. A tremendous research effort has recently been devoted to TI-based ...Topological insulators （Tls） are bulk insulators that possess robust helical conducting states along their interfaces with conventional insulators. A tremendous research effort has recently been devoted to TI-based heterostructures, in which con- ventional proximity effects give rise to a series of exotic physical phenomena. This paper reviews our recent studies on the potential existence of topological proximity effects at the interface between a topological insulator and a normal insu- lator or other topologically trivial systems. Using first-principles approaches, we have realized the tunability of the vertical location of the topological helical state via intriguing dual-proximity effects. To further elucidate the control parameters of this effect, we have used the graphene-based heterostructures as prototypical systems to reveal a more complete phase diagram. On the application side of the topological helical states, we have presented a catalysis example, where the topo- logical helical state plays an essential role in facilitating surface reactions by serving as an effective electron bath, These discoveries lay the foundation for accurate manipulation of the real space properties of the topological helical state in TI- based heterostructures and pave the way for realization of the salient functionality of topological insulators in future device applications.展开更多
Based on first-principles density functional theory calculation,we discover a novel form of spin-orbit(SO)splitting in two-dimensional(2D)heterostructures composed of a single Bi(111)bilayer stacking with a 2D semicon...Based on first-principles density functional theory calculation,we discover a novel form of spin-orbit(SO)splitting in two-dimensional(2D)heterostructures composed of a single Bi(111)bilayer stacking with a 2D semiconducting In_(2)Se_(2) or a 2D ferroelectricα-In_(2)Se_(3) layer.Such SO splitting has a Rashba-like but distinct spin texture in the valence band around the maximum,where the chirality of the spin texture reverses within the upper spin-split branch,in contrast to the conventional Rashba systems where the upper branch and lower branch have opposite chirality solely in the region below the band crossing point.The ferroelectric nature ofα-In_(2)Se_(3) further enables the tuning of the spin texture upon the reversal of the electric polarization with the application of an external electric field.Detailed analysis based on a tight-binding model reveals that such SO splitting texture results from the interplay of complex orbital characters and substrate interaction.This finding enriches the diversity of SO splitting systems and is also expected to promise for spintronic applications.展开更多
Excitons in solid state are bosons generated by electron-hole pairs as the Coulomb screening is sufficiently reduced.The exciton condensation can result in exotic physics such as super-fluidity and insulating state.In...Excitons in solid state are bosons generated by electron-hole pairs as the Coulomb screening is sufficiently reduced.The exciton condensation can result in exotic physics such as super-fluidity and insulating state.In charge density wave(CDW)state,1T-TiSe_(2) is one of the candidates that may host the exciton condensation.However,to envision its excitonic effect is still challenging,particularly at the two-dimensional limit,which is applicable to future devices.Here,we realize the epitaxial 1T-TiSe_(2) bilayer,the two-dimensional limit for its 2×2×2 CDW order,to explore the exciton-associated effect.By means of high-resolution scanning tunneling spectroscopy and quasiparticle interference,we discover an unexpected state residing below the conduction band and right within the CDW gap region.As corroborated by our theoretical analysis,this mysterious phenomenon is in good agreement with the electron-exciton coupling.Our study provides a material platform to explore exciton-based electronics and opto-electronics.展开更多
基金supported by the CAS Project for Young Scientists in Basic Research(Grant No.YSBR-046)the National Natural Science Foundation of China(Grant Nos.92165201,11974324,12104435)+4 种基金the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302800)the Anhui Initiative in Quantum Information Technologies(Grant No.AHY170000)Hefei Science Center CAS(Grant No.2020HSC-UE014)the Fundamental Research Funds for the Central Universities(Grant Nos.WK3510000013 and WK2310000104)supported by USTC Tang Scholar。
文摘Epitaxial graphene grown on silicon carbide(Si C/graphene)is a promising solution for achieving a highprecision quantum Hall resistance standard.Previous research mainly focused on the quantum resistance metrology of n-type Si C/graphene,while a comprehensive understanding of the quantum resistance metrology behavior of graphene with different doping types is lacking.Here,we fabricated both n-and p-type Si C/graphene devices via polymer-assisted molecular adsorption and conducted systematic magneto-transport measurements in a wide parameter space of carrier density and temperature.It is demonstrated that n-type devices show greater potential for development of quantum resistance metrology compared with p-type devices,as evidenced by their higher carrier mobility,lower critical magnetic field for entering quantized Hall plateaus,and higher robustness of the quantum Hall effect against thermal degeneration.These discrepancies can be reasonably attributed to the weaker scattering from molecular dopants for n-type devices,which is further supported by the analyses on the quantum interference effect in multiple devices.These results enrich our understanding of the charged impurity on electronic transport performance of graphene and,more importantly,provide a useful reference for future development of graphene-based quantum resistance metrology.
基金Computational support was provided by Supercomputing Center in USTC and National Supercomputing Center in Tianjinthe National Key Research and Development Program of China(Grant Nos.2017YFA0204904 and 2019YFA0210004)。
文摘A machine learning(ML)potential for Au clusters is developed through training on a dataset including several different sized clusters.This ML potential accurately covers the whole configuration space of Au clusters in a broad size range,thus expressing a good performance in search of their global minimum energy structures.Based on our potential,the low-lying structures of 17 different sized Au clusters are identified,which shows that small sized Au clusters tend to form planar structures while large ones are more likely to be stereo,revealing the critical size for the two-dimensional(2D)to three-dimensional(3D)structural transition.Our calculations demonstrate that ML is indeed powerful in describing the interaction of Au atoms and provides a new paradigm on accelerating the search of structures.
基金supported by the National Natural Science Foundation of China(Grant Nos.92165201 and 11974324)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302800)+3 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDC07010000)the Anhui Initiative in Quantum Information Technologies(Grant No.AHY170000)the Hefei Science Center CAS(Grant No.2020HSC-UE014)the Fundamental Research Funds for the Central Universities(Grant No.WK3510000013)。
文摘For conductors in the ballistic regime, electron-boundary scattering at the sample edge plays a dominant role in determining the transport performance, giving rise to many intriguing phenomena like low-field negative magnetoresistance effect. We systematically investigate the magneto-transport behaviors of BN-encapsulated graphene devices with narrow channel width W, wherein the bulk mean free path Lmfp can be very large and highly tunable. By comparing the magnetoresistance features and the amplitude of Lmfp in a large parameter space of temperature and carrier density, we reveal that the boundary-scattering-dominated negative magnetoresistance effect can still survive even when the ballistic ratio(Lmfp/W) is as low as 0.15. This striking value is much smaller than the expected value for achieving(quasi-) ballistic transport regime(Lmfp/W ≥ 1), and can be attributed to the ultra-low specularity of the sample edge of our graphene devices. These findings enrich our understanding of the effects of boundary scattering on channel transport, which is of vital importance for future designs of two-dimensional electronic devices with limited lateral sizes.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2017YFA0204904 and 2019YFA0210004)the National Natural Science Foundation of China(Grant No.11634011)+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB30000000)the Fundamental Research Funds for the Central Universities(Grant No.WK2340000082)。
文摘Based on first-principles calculations,a two-dimensional(2D)van der Waals(vd W)bilayer heterostructure consisting of two topologically trivial ferromagnetic(FM)monolayers CrI_(3)and ScCl_(2)is proposed to realize the quantum anomalous Hall effect(QAHE)with a sizable topologically nontrivial band gap of 4.5 me V.Its topological nature is attributed to an interlayer band inversion between the monolayers and critically depends on the symmetry of the stacking configuration.We further demonstrate that the topologically nontrivial band gap can be increased nearly linearly by the application of a perpendicular external pressure and reaches 8.1 me V at 2.7 GPa,and the application of an external out-of-plane electric field can also modulate the band gap and convert the system back to topologically trivial via eliminating the band inversion.An effective model is developed to describe the topological phase evolution in this bilayer heterostructure.This work provides a new candidate system based on 2D vd W materials for realization of potential high-temperature QAHE with considerable controllability.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.12374196,92165201,11634011,and 22109153)the Innovation Program for Quantum Science and Technology (Grant No.2021ZD0302800)+4 种基金the CAS Project for Young Scientists in Basic Research (Grant No.YSBR-046)the Fundamental Research Funds for the Central Universities (Grant Nos.WK3510000006 and WK3430000003)the Fund of Anhui Initiative in Quantum Information Technologies (Grant No.AHY170000)the University Synergy Innovation Program of Anhui Province,China (Grant No.GXXT-2022-008)the National Synchrotron Radiation Laboratory Joint Funds of University of Science and Technology of China (Grant No.KY2060000241)。
文摘Novel two-dimensional thermoelectric materials have attracted significant attention in the field of thermoelectric due to their low lattice thermal conductivity.A comprehensive understanding of their microscopic structures is crucial for driving further the optimization of materials properties and developing novel functional materials.Here,by using in situ scanning tunneling microscopy,we report the atomic layer evolution and surface reconstruction on the cleaved thermoelectric material KCu_(4)Se_(3) for the first time.We clearly revealed each atomic layer,including the naturally cleaved K atomic layer,the intermediate Se^(2-)atomic layer,and the Se^(-)atomic layer that emerges in the thermodynamic-stable state.Departing from the maj ority of studies that predominantly concentrate on macroscopic measurements of the charge transport,our results reveal the coexistence of potassium disorder and complex reconstructed patterns of selenium,which potentially influences charge carrier and lattice dynamics.These results provide direct insight into the surface microstructures and evolution of KCu_(4)Se_(3),and shed useful light on designing functional materials with superior performance.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2017YFA0204904 and 2019YFA0210004)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB30000000)the Fundamental Research Funds for the Central Universities,China(Grant No.WK3510000013).
文摘Monolayer transition metal dichalcogenides can normally exist in several structural polymorphs with distinct electrical,optical,and catalytic properties.Effective control of the relative stability and transformation of different phases in these materials is thus of critical importance for applications.Using density functional theory calculations,we investigate the effects of low-work-function metal substrates including Ti,Zr,and Hf on the structural,electronic,and catalytic properties of monolayer MoS_(2) and WS_(2).The results indicate that such substrates not only convert the energetically stable structure from the 1H phase to the 1T'/1T phase,but also significantly reduce the kinetic barriers of the phase transformation.Furthermore,our calculations also indicate that the 1T' phase of MoS_(2) with Zr or Hf substrate is a potential catalyst for the hydrogen evolution reaction.
基金Supported by the National Natural Science Foundation of China (Grant Nos.11974324,11804326 and U1832151)the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No.XDC07010000)+2 种基金the National Key Research and Development Program of China (Grant No.2017YFA0403600)Anhui Initiative in Quantum Information Technologies (Grant No.AHY170000)Hefei Science Center CAS (Grant No.2018HSC-UE014)。
文摘Hybrid structures of two distinct materials provide an excellent opportunity to optimize functionalities.We report the realization of wide quantum Hall plateaus in graphene field-effect devices on the LaAlO3/SrTiO3 heterostructures.Well-defined quantized Hall resistance plateaus at filling factors ν=±2 can be obtained over wide ranges of the magnetic field and gate voltage,e.g.,extending from 2 T to a maximum available magnetic field of 9 T.By using a simple band diagram model,it is revealed that these wide plateaus arise from the ultralarge capacitance of the ultra-thin LAO layer acting as the dielectric layer.This is distinctly different from the case of epitaxial graphene on Si C substrates,where the realization of giant Hall plateaus relies on the charge transfer between the graphene layer and interface states in SiC.Our results offer an alternative route towards optimizing the quantum Hall performance of graphene,which may find its applications in the further development of quantum resistance metrology.
基金Project supported by the National Key Basic Research Program of China(Grant No.2017YFA0205004)the National Natural Science Foundation of China(Grant Nos.92165201,11474261,and 11634011)+1 种基金the Fundamental Research Funds for the Central Universities(Grant Nos.WK3510000006,and WK3430000003)the Anhui Initiative in Quantum Information Technologies(Grant No.AHY170000)。
文摘Nanoclusters consisting of a few atoms have attracted a lot of research interests due to their exotic size-dependent properties. Here, well-ordered two-dimensional Sb cluster superlattice was fabricated on Si substrate by a two-step method and characterized by scanning tunneling microscopy. High resolution scanning tunneling microscope measurements revealed the fine structures of the Sb clusters, which consist of several Sb atoms ranging from 2 to 7. Furthermore, the electronic structure of the nanocluster displays the quantized energy-level which is due to the single-electron tunneling effects. We believe that the fabrication of Sb cluster superlattice broadens the species of the cluster superlattice and provides a promising candidate to further explore the novel physical and chemical properties of the semimetal nanocluster.
基金supported by the National Natural Science Foundation of China (Grant Nos. 91021019, 51074151, and 11034006)the National Basic Research Program of China (Grant Nos. 2010CB923401 and 2011CB921801)+2 种基金USDOE (Grant No. DE-FG03-02ER45958)US National Science Foundation (Grant No. 0906025)the BES Program of US Department of Energy (Grant No. ER45958)
文摘Topological insulators （Tls） are bulk insulators that possess robust helical conducting states along their interfaces with conventional insulators. A tremendous research effort has recently been devoted to TI-based heterostructures, in which con- ventional proximity effects give rise to a series of exotic physical phenomena. This paper reviews our recent studies on the potential existence of topological proximity effects at the interface between a topological insulator and a normal insu- lator or other topologically trivial systems. Using first-principles approaches, we have realized the tunability of the vertical location of the topological helical state via intriguing dual-proximity effects. To further elucidate the control parameters of this effect, we have used the graphene-based heterostructures as prototypical systems to reveal a more complete phase diagram. On the application side of the topological helical states, we have presented a catalysis example, where the topo- logical helical state plays an essential role in facilitating surface reactions by serving as an effective electron bath, These discoveries lay the foundation for accurate manipulation of the real space properties of the topological helical state in TI- based heterostructures and pave the way for realization of the salient functionality of topological insulators in future device applications.
基金Project supported by the Science Fund from the Ministry of Science and Technology of China(Grant Nos.2017YFA0204904 and 2019YFA0210004)the National Natural Science Foundation of China(Grant Nos.11674299 and 11634011)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB30000000)the Fund of Anhui Initiative Program in Quantum Information Technologies(Grant No.AHY170000)the Fundamental Research Funds for the Central Universities,China(Grant No.WK3510000013).
文摘Based on first-principles density functional theory calculation,we discover a novel form of spin-orbit(SO)splitting in two-dimensional(2D)heterostructures composed of a single Bi(111)bilayer stacking with a 2D semiconducting In_(2)Se_(2) or a 2D ferroelectricα-In_(2)Se_(3) layer.Such SO splitting has a Rashba-like but distinct spin texture in the valence band around the maximum,where the chirality of the spin texture reverses within the upper spin-split branch,in contrast to the conventional Rashba systems where the upper branch and lower branch have opposite chirality solely in the region below the band crossing point.The ferroelectric nature ofα-In_(2)Se_(3) further enables the tuning of the spin texture upon the reversal of the electric polarization with the application of an external electric field.Detailed analysis based on a tight-binding model reveals that such SO splitting texture results from the interplay of complex orbital characters and substrate interaction.This finding enriches the diversity of SO splitting systems and is also expected to promise for spintronic applications.
基金the National Key Research and Development Program of China(Grant Nos.2021YFA1400403,2018YFA0306800,2019YFA0210004,and 2016YFA0300401)the National Natural Science Foundation of China(Grant Nos.92165205,11774149,11790311,11774154,11674158,and 12074175)Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302800)。
文摘Excitons in solid state are bosons generated by electron-hole pairs as the Coulomb screening is sufficiently reduced.The exciton condensation can result in exotic physics such as super-fluidity and insulating state.In charge density wave(CDW)state,1T-TiSe_(2) is one of the candidates that may host the exciton condensation.However,to envision its excitonic effect is still challenging,particularly at the two-dimensional limit,which is applicable to future devices.Here,we realize the epitaxial 1T-TiSe_(2) bilayer,the two-dimensional limit for its 2×2×2 CDW order,to explore the exciton-associated effect.By means of high-resolution scanning tunneling spectroscopy and quasiparticle interference,we discover an unexpected state residing below the conduction band and right within the CDW gap region.As corroborated by our theoretical analysis,this mysterious phenomenon is in good agreement with the electron-exciton coupling.Our study provides a material platform to explore exciton-based electronics and opto-electronics.
