Lattice dynamics of ^(36)Ar are investigated by Keating model.Owing to the short-range character of the interactions in rare-gas solids,only the nearest neighbour interactions were taken into account.The calculated ph...Lattice dynamics of ^(36)Ar are investigated by Keating model.Owing to the short-range character of the interactions in rare-gas solids,only the nearest neighbour interactions were taken into account.The calculated phonon frequencies and elastic constants are in good agreement with the experimental values.The maximum error for phonon frenquencies is 3.3% and for the elastic constants is 7%.展开更多
The monolayer adsorbed Mo(001)surface is studied by the slab dynamical calculation by using the nearest and next nearest neighbour interactions.The phase diagram is obtained for light,heavy atom adsorbed and clean Mo(...The monolayer adsorbed Mo(001)surface is studied by the slab dynamical calculation by using the nearest and next nearest neighbour interactions.The phase diagram is obtained for light,heavy atom adsorbed and clean Mo(001)surface.The surface reconstruction induced by the interactions between adsorbed atoms is dicussed.展开更多
We systematically investigate the motion of slowly moving matter wave gap solitons in a nonlinear potential, produced by the weak random spatial variation of the atomic scattering length. With the weak randomness, we ...We systematically investigate the motion of slowly moving matter wave gap solitons in a nonlinear potential, produced by the weak random spatial variation of the atomic scattering length. With the weak randomness, we construct an effective-particle theory to study the motion of gap solitons. Based on the effective-particle theory, the effect of the randomness on gap solitons is obtained, and the motion of gap solitons is finally solved. Moreover, the analytic results for the general behaviours of gap soliton motion, such as the ensemble-average speed and the reflection probability depending on the weak randomness are obtained. We find that with the increase of the random strength the ensemble-average speed of gap solitons decreases slowly where the reduction is proportional to the variance of the weak randomness, and the reflection probability becomes larger. The theoretical results are in good agreement with the numerical simulations based on the Cross-Pitaevskii equation.展开更多
In addition to non-radiative guided modes, two-dimensional photonic-crystal slabs support guided resonant ones which can radiate into free space. From the polarization states of these guided resonances, a polarization...In addition to non-radiative guided modes, two-dimensional photonic-crystal slabs support guided resonant ones which can radiate into free space. From the polarization states of these guided resonances, a polarization field on a photonic band can be constructed in momentum space. Momentum-space polarization fields display complicated configurations and patterns with different types of polarization singularities inside, shedding new light on the manipulations of light flows.In this review, we summarize the recent research progress on momentum-space polarization fields and singularities in two-dimensional photonic-crystal slabs, focusing on their unique optical properties and potential applications as well.展开更多
It is well known that spatial symmetry in a photonic crystal(PhC)slab is capable of creating bound states in the continuum(BICs),which can be characterized by topological charges of polarization vortices.Here,we show ...It is well known that spatial symmetry in a photonic crystal(PhC)slab is capable of creating bound states in the continuum(BICs),which can be characterized by topological charges of polarization vortices.Here,we show that when a PT-symmetric perturbation is introduced into the PhC slab,a new type of BICs(pt-BICs)will arise from each ordinary BIC together with the creation of rings of lasing threshold modes with pt-BICs embedded in these rings.Different from ordinary BICs,the Q-factor divergence rate of a pt-BIC is reduced and anisotropic in momentum space.Also,pt-BICs can even appear at off-high symmetry lines of the Brillouin zone.The pt-BICs also carry topological charges and can be created or annihilated with the total charge conserved.A unified picture on pt-BICs and the associated lasing threshold modes is given based on the temporal coupled mode theory.Our findings reveal the new physics arising from the interplay between PT symmetry and BIC in PhC slabs.展开更多
We demonstrate theoretically that two-dimensional photonic bandgap materials are indeed perfect polarizers provided that they have a proper photonic band structure along the incident direction of light.This kind of po...We demonstrate theoretically that two-dimensional photonic bandgap materials are indeed perfect polarizers provided that they have a proper photonic band structure along the incident direction of light.This kind of polarizer is fundamentally different from the conventional ones.It can function in a wide frequency range with high performance and its size can be made very compact,which renders it useful as a micropolarizer in micro-optics.展开更多
文摘Lattice dynamics of ^(36)Ar are investigated by Keating model.Owing to the short-range character of the interactions in rare-gas solids,only the nearest neighbour interactions were taken into account.The calculated phonon frequencies and elastic constants are in good agreement with the experimental values.The maximum error for phonon frenquencies is 3.3% and for the elastic constants is 7%.
文摘The monolayer adsorbed Mo(001)surface is studied by the slab dynamical calculation by using the nearest and next nearest neighbour interactions.The phase diagram is obtained for light,heavy atom adsorbed and clean Mo(001)surface.The surface reconstruction induced by the interactions between adsorbed atoms is dicussed.
基金Supported by the National Key Basic Research Special Fund of China, the National Natural Science Foundation of China, and the Shanghai Science and Technology Commission.
基金Project supported by the National Basic Research Program of China (Grant No 2006CB921701-6)Pujiang Talent Project (Grant No PJ2005(00593))the Hundred Tarent Project of the Chinese Academy of Sciences, China
文摘We systematically investigate the motion of slowly moving matter wave gap solitons in a nonlinear potential, produced by the weak random spatial variation of the atomic scattering length. With the weak randomness, we construct an effective-particle theory to study the motion of gap solitons. Based on the effective-particle theory, the effect of the randomness on gap solitons is obtained, and the motion of gap solitons is finally solved. Moreover, the analytic results for the general behaviours of gap soliton motion, such as the ensemble-average speed and the reflection probability depending on the weak randomness are obtained. We find that with the increase of the random strength the ensemble-average speed of gap solitons decreases slowly where the reduction is proportional to the variance of the weak randomness, and the reflection probability becomes larger. The theoretical results are in good agreement with the numerical simulations based on the Cross-Pitaevskii equation.
基金supported by the National Natural Science Foundation of China(Grant Nos.11727811 and 91963212)the National Key Basic Research Program of China(Grant No.2018YFA0306201)Science and Technology Commission of Shanghai Municipality(Grant Nos.19XD1434600,2019SHZDZX01,19DZ2253000,and 20501110500)。
文摘In addition to non-radiative guided modes, two-dimensional photonic-crystal slabs support guided resonant ones which can radiate into free space. From the polarization states of these guided resonances, a polarization field on a photonic band can be constructed in momentum space. Momentum-space polarization fields display complicated configurations and patterns with different types of polarization singularities inside, shedding new light on the manipulations of light flows.In this review, we summarize the recent research progress on momentum-space polarization fields and singularities in two-dimensional photonic-crystal slabs, focusing on their unique optical properties and potential applications as well.
基金the National Natural Science Foundation of China(Grant Nos.12074049,11727811,and 12047564)the Hong Kong Research Grants Council(Grant Nos.Ao E/P-02/12,16303119,and N HKUST608/17)the Fundamental Research Funds for the Central Universities(Grant Nos.2020CDJQY-Z006 and 2020CDJQY-Z003)。
文摘It is well known that spatial symmetry in a photonic crystal(PhC)slab is capable of creating bound states in the continuum(BICs),which can be characterized by topological charges of polarization vortices.Here,we show that when a PT-symmetric perturbation is introduced into the PhC slab,a new type of BICs(pt-BICs)will arise from each ordinary BIC together with the creation of rings of lasing threshold modes with pt-BICs embedded in these rings.Different from ordinary BICs,the Q-factor divergence rate of a pt-BIC is reduced and anisotropic in momentum space.Also,pt-BICs can even appear at off-high symmetry lines of the Brillouin zone.The pt-BICs also carry topological charges and can be created or annihilated with the total charge conserved.A unified picture on pt-BICs and the associated lasing threshold modes is given based on the temporal coupled mode theory.Our findings reveal the new physics arising from the interplay between PT symmetry and BIC in PhC slabs.
基金Supported in part by the National Natural Science Foundation of China under Grant No.69625609,Pandeng plan(Y-41)Shanghai Science and Technology Commission.
文摘We demonstrate theoretically that two-dimensional photonic bandgap materials are indeed perfect polarizers provided that they have a proper photonic band structure along the incident direction of light.This kind of polarizer is fundamentally different from the conventional ones.It can function in a wide frequency range with high performance and its size can be made very compact,which renders it useful as a micropolarizer in micro-optics.
