Electronic and optical properties of materials are affected by atomic motion through the electron–phonon interaction:not only band gaps change with temperature,but even at absolute zero temperature,zero-point motion ...Electronic and optical properties of materials are affected by atomic motion through the electron–phonon interaction:not only band gaps change with temperature,but even at absolute zero temperature,zero-point motion causes band-gap renormalization.We present a large-scale first-principles evaluation of the zero-point renormalization of band edges beyond the adiabatic approximation.For materials with light elements,the band gap renormalization is often larger than 0.3 eV,and up to 0.7 eV.This effect cannot be ignored if accurate band gaps are sought.For infrared-active materials,global agreement with available experimental data is obtained only when non-adiabatic effects are taken into account.They even dominate zero-point renormalization for many materials,as shown by a generalized Fröhlich model that includes multiple phonon branches,anisotropic and degenerate electronic extrema,whose range of validity is established by comparison with first-principles results.展开更多
We review some recent progress in the exploration of pseudospin-1 physics using dielectric photonic crystals(PCs).We show some physical implications of the PCs exhibiting an accidental degeneracy induced conical dispe...We review some recent progress in the exploration of pseudospin-1 physics using dielectric photonic crystals(PCs).We show some physical implications of the PCs exhibiting an accidental degeneracy induced conical dispersion at theΓpoint,such as the realization of zero refractive index medium and the zero Berry phase of a loop around the nodal point.Te photonic states of such PCs near the Dirac-like point can be described by an efective spin-orbit Hamiltonian of pseudospin-1.Te wave propagation in the positive,negative,and zero index media can be unifed within a framework of pseudospin-1 description.A scale change in PCs results in a rigid band shif of the Dirac-like cone,allowing for the manipulation of waves in pseudospin-1 systems in much the same way as applying a gate voltage in pseudospin-1/2 graphene.Te transport of waves in pseudospin-1 systems exhibits many interesting phenomena,including super Klein tunneling,robust supercollimation,and unconventional Anderson localization.Te transport properties of pseudospin-1 systems are distinct from their counterparts in pseudospin-1/2 systems,which will also be presented for comparison.展开更多
基金This work has been supported by the Fonds de la Recherche Scientifique(FRS-FNRS Belgium)through the PdR Grant No.T.0238.13-AIXPHOthe PdR Grant No.T.0103.19-ALPS+7 种基金the Fonds de Recherche du Québec Nature et Technologie(FRQ-NT)the Natural Sciences and Engineering Research Council of Canada(NSERC)under grants RGPIN-2016-06666Computational resources have been provided by the supercomputing facilities of the Universitécatholique de Louvain(CISM/UCL)the Consortium des Equipements de Calcul Intensif en Fédération Wallonie Bruxelles(CECI)funded by the FRS-FNRS under Grant No.2.5020.11the Tier-1 supercomputer of the Fédération Wallonie-Bruxelles,infrastructure funded by the Walloon Region under the grant agreement No.1117545as well as the Canadian Foundation for Innovation,the Ministère de l’Éducation des Loisirs et du Sport(Québec),Calcul Québec,and Compute Canada.This work was supported by the Center for Computational Study of Excited-State Phenomena in Energy Materials(C2SEPEM)at the Lawrence Berkeley National Laboratory,which is funded by the U.S.Department of Energy,Office of Science,Basic Energy Sciences,Materials Sciences and Engineering Division under Contract No.DE-AC02-05CH11231as part of the Computational Materials Sciences Program(advanced algorithms/codes)and by the National Science Foundation under grant DMR-1926004(basic theory and formalism)This research used resources of the National Energy Research Scientific Computing Center(NERSC),a DOE Office of Science User Facility supported by the Office of Science of the U.S.Department of Energy under Contract No.DE-AC02-05CH11231.
文摘Electronic and optical properties of materials are affected by atomic motion through the electron–phonon interaction:not only band gaps change with temperature,but even at absolute zero temperature,zero-point motion causes band-gap renormalization.We present a large-scale first-principles evaluation of the zero-point renormalization of band edges beyond the adiabatic approximation.For materials with light elements,the band gap renormalization is often larger than 0.3 eV,and up to 0.7 eV.This effect cannot be ignored if accurate band gaps are sought.For infrared-active materials,global agreement with available experimental data is obtained only when non-adiabatic effects are taken into account.They even dominate zero-point renormalization for many materials,as shown by a generalized Fröhlich model that includes multiple phonon branches,anisotropic and degenerate electronic extrema,whose range of validity is established by comparison with first-principles results.
基金This work was supported by a grant from the Research Grants Council of the Hong Kong(Project No.AoE/P-02/12)S.G.L.also acknowledges support by the National Science Foundation under Grant No.DMR-1508412.
文摘We review some recent progress in the exploration of pseudospin-1 physics using dielectric photonic crystals(PCs).We show some physical implications of the PCs exhibiting an accidental degeneracy induced conical dispersion at theΓpoint,such as the realization of zero refractive index medium and the zero Berry phase of a loop around the nodal point.Te photonic states of such PCs near the Dirac-like point can be described by an efective spin-orbit Hamiltonian of pseudospin-1.Te wave propagation in the positive,negative,and zero index media can be unifed within a framework of pseudospin-1 description.A scale change in PCs results in a rigid band shif of the Dirac-like cone,allowing for the manipulation of waves in pseudospin-1 systems in much the same way as applying a gate voltage in pseudospin-1/2 graphene.Te transport of waves in pseudospin-1 systems exhibits many interesting phenomena,including super Klein tunneling,robust supercollimation,and unconventional Anderson localization.Te transport properties of pseudospin-1 systems are distinct from their counterparts in pseudospin-1/2 systems,which will also be presented for comparison.
