We demonstrate the coherent interactions of lattice soliton trains, including in-band solitons （IBSs） and gap soliton trains （GSTs）, in optically induced two-dimensional photonic lattices with self-defocusing nonl...We demonstrate the coherent interactions of lattice soliton trains, including in-band solitons （IBSs） and gap soliton trains （GSTs）, in optically induced two-dimensional photonic lattices with self-defocusing nonlinearity. It is revealed that the π-staggered phase structures of the lattice soliton trains will lead to anomalous interactions. Solely by changing their initial separations, the transition between attractive and repulsive interaction forces or reversion of the energy transfer can be obtained. The ‘negative refraction＇ effect of the soliton trains on the interaction is also discussed. Moreover, two interacting IBSs can merge into one GST when attraction or energy transfer happens.展开更多
The microRaman scattering of 4H-SiC films, fabricated by low pressure chemical vapor deposition under different growth conditions, is investigated at temperatures ranging from 80 K to 550K. The effects of growth condi...The microRaman scattering of 4H-SiC films, fabricated by low pressure chemical vapor deposition under different growth conditions, is investigated at temperatures ranging from 80 K to 550K. The effects of growth conditions on E2 （TO）, E1 （TO） and A1 （LO） phonon mode frequencies are negligible. The temperature dependences of phonon linewidth and lifetime of E2 （TO） modes are analyzed in terms of an anharmonic damping effect induced by thermal and growth conditions. The results show that the lifetime of E2 （TO） mode increases when the quality of the sample improves. Unlike other phone modes, Raman shift of A1 （longitudinal optical plasma coupling （LOPC）） mode does not decrease monotonously when the temperature increases, but tends to blueshift at low temperatures and to redshift at relatively high temperatures. Theoretical analyses are given for the abnormal phenomena of A1 （LOPC） mode in 4H-SiC.展开更多
Multiferroic materials,showing the coexistence and coupling of ferroelectric and magnetic orders,are of great technological and fundamental importance.However,the limitation of single phase multiferroics with robust m...Multiferroic materials,showing the coexistence and coupling of ferroelectric and magnetic orders,are of great technological and fundamental importance.However,the limitation of single phase multiferroics with robust magnetization and polarization hinders the magnetoelectric effect from being applied practically.Magnetic frustration,which can induce ferroelectricity,gives rise to multiferroic behavior.In this paper,we attempt to construct an artificial magnetically frustrated structure comprised of manganites to induce ferroelectricity.A disordered stacking of manganites is expected to result in frustration at interfaces.We report here that a tri-color multilayer structure comprised of non-ferroelectric La;Ca;MnO;（A）/Pr;Ca;MnO;（B）/Pr;Sr;MnO;（C） layers with the disordered arrangement of ABC-ACBCAB-CBA-BAC-BCA is prepared to form magnetoelectric multiferroics.The multilayer film exhibits evidence of ferroelectricity at room temperature,thus presenting a candidate for multiferroics.展开更多
In this paper, the morphological transition from dendrite to symmetry-broken dendrite is investigated in the directional ;olidification of non-axially-oriented crystals using a quantitative phase-field model. The effe...In this paper, the morphological transition from dendrite to symmetry-broken dendrite is investigated in the directional ;olidification of non-axially-oriented crystals using a quantitative phase-field model. The effects of pulling velocity and zrystal orientation on the morphological transition are investigated. The results indicate the orientation dependence of the ;ymmetry-broken double dendrites. A dendrite to symmetry-broken dendrite transition is found by varying the pulling telocity at different crystal orientations and the symmetry-broken multiple dendrites emerge as a transition state for the ;ymmetry-broken double dendrites. The state region during the transition can be well characterized through the variations ff the characteristic angle and the average primary dendritic spacing.展开更多
A regularization of the surface tension anisotropic function used in vapor-liquid-solid nanowire growth was introduced into the quantitative phase-field model to simulate the faceted growth in solidification of alloys...A regularization of the surface tension anisotropic function used in vapor-liquid-solid nanowire growth was introduced into the quantitative phase-field model to simulate the faceted growth in solidification of alloys.Predicted results show that the value of δ can only affect the region near the tip,and the convergence with respect to δ can be achieved with the decrease of δ near the tip.It can be found that the steady growth velocity is not a mo no tonic function of the cusp amplitude,and the maximum value is approximately at ε=0.8 when the supersaturation is fixed.Moreover,the growth velocity is an increasing function of supersaturation with the morphological transition from facet to dendrite.展开更多
基金Project supported by the Northwestern Polytechnical University (NPU) Foundation for Fundamental Research and the Doctorate Foundation of NPU (Grant No.CX200914)
文摘We demonstrate the coherent interactions of lattice soliton trains, including in-band solitons （IBSs） and gap soliton trains （GSTs）, in optically induced two-dimensional photonic lattices with self-defocusing nonlinearity. It is revealed that the π-staggered phase structures of the lattice soliton trains will lead to anomalous interactions. Solely by changing their initial separations, the transition between attractive and repulsive interaction forces or reversion of the energy transfer can be obtained. The ‘negative refraction＇ effect of the soliton trains on the interaction is also discussed. Moreover, two interacting IBSs can merge into one GST when attraction or energy transfer happens.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61176085,11474365 and 61377055the Department of Education of Guangdong Province under Grant No gjhz1103the Open-Project Program of the State Key laboratory of Opto-Electronic Material and Technologies of Sun Yatsen University
文摘The microRaman scattering of 4H-SiC films, fabricated by low pressure chemical vapor deposition under different growth conditions, is investigated at temperatures ranging from 80 K to 550K. The effects of growth conditions on E2 （TO）, E1 （TO） and A1 （LO） phonon mode frequencies are negligible. The temperature dependences of phonon linewidth and lifetime of E2 （TO） modes are analyzed in terms of an anharmonic damping effect induced by thermal and growth conditions. The results show that the lifetime of E2 （TO） mode increases when the quality of the sample improves. Unlike other phone modes, Raman shift of A1 （longitudinal optical plasma coupling （LOPC）） mode does not decrease monotonously when the temperature increases, but tends to blueshift at low temperatures and to redshift at relatively high temperatures. Theoretical analyses are given for the abnormal phenomena of A1 （LOPC） mode in 4H-SiC.
基金supported by the National Natural Science Foundation of China(Grant Nos.61471301,61078057,51172183,51402240,and 51471134)the Specialized Research Fund for the Doctoral Program of Higher Education,China(Grant No.20126102110045)+1 种基金the Natural Science Foundation of Shaanxi Province,China(Grant No.2015JQ5125)the Fundamental Research Funds for the Central Universities,China(Grant No.3102015ZY078)
文摘Multiferroic materials,showing the coexistence and coupling of ferroelectric and magnetic orders,are of great technological and fundamental importance.However,the limitation of single phase multiferroics with robust magnetization and polarization hinders the magnetoelectric effect from being applied practically.Magnetic frustration,which can induce ferroelectricity,gives rise to multiferroic behavior.In this paper,we attempt to construct an artificial magnetically frustrated structure comprised of manganites to induce ferroelectricity.A disordered stacking of manganites is expected to result in frustration at interfaces.We report here that a tri-color multilayer structure comprised of non-ferroelectric La;Ca;MnO;（A）/Pr;Ca;MnO;（B）/Pr;Sr;MnO;（C） layers with the disordered arrangement of ABC-ACBCAB-CBA-BAC-BCA is prepared to form magnetoelectric multiferroics.The multilayer film exhibits evidence of ferroelectricity at room temperature,thus presenting a candidate for multiferroics.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61078057 and 51172183)the National Natural Science Foundation of Shaanxi Province,China(Grant No.2012JQ8013)+1 种基金the Aviation Foundation of China(Grant No.2011ZF53065)the NPU Foundation for Fundamental Research,China(Grant Nos.NPU-FFR-JC20110273 and JC201155)
文摘In this paper, the morphological transition from dendrite to symmetry-broken dendrite is investigated in the directional ;olidification of non-axially-oriented crystals using a quantitative phase-field model. The effects of pulling velocity and zrystal orientation on the morphological transition are investigated. The results indicate the orientation dependence of the ;ymmetry-broken double dendrites. A dendrite to symmetry-broken dendrite transition is found by varying the pulling telocity at different crystal orientations and the symmetry-broken multiple dendrites emerge as a transition state for the ;ymmetry-broken double dendrites. The state region during the transition can be well characterized through the variations ff the characteristic angle and the average primary dendritic spacing.
基金Project supported by the National Key Research and Development Program of China(Grant No.2018YFB2001800)the National Natural Science Foundation of China(Grant No.21978298)+2 种基金the Natural Science Foundation of Shaanxi Province in China(Grant No.2020JM-111)Applied Basic Research Key Project of Yunnan,China(Grant No.202002AB080001-1)Henan Youth Talent Promotion Project.China(Grant No.2020HYTP019)。
文摘A regularization of the surface tension anisotropic function used in vapor-liquid-solid nanowire growth was introduced into the quantitative phase-field model to simulate the faceted growth in solidification of alloys.Predicted results show that the value of δ can only affect the region near the tip,and the convergence with respect to δ can be achieved with the decrease of δ near the tip.It can be found that the steady growth velocity is not a mo no tonic function of the cusp amplitude,and the maximum value is approximately at ε=0.8 when the supersaturation is fixed.Moreover,the growth velocity is an increasing function of supersaturation with the morphological transition from facet to dendrite.
