Broadband strong optical dichroism in topological Dirac semimetals with Fermi velocity anisotropy  

作　　者：J Lim K J A Ooi C Zhang L K Ang Yee Sin Ang 林镇杰;黄健安;涨潮;洪礼祺;洪逸欣(Science,Math and Technology,Singapore University of Technology and Design,Singapore;School of Energy and Chemical Engineering,Xiamen University Malaysia,Selangor Darul Ehsan 43900,Malaysia;College of Chemistry and Chemical Engineering,Xiamen University,Xiamen 361005,China;School of Physics,University of Wollongong,Northfields Avenue,New South Wales 2522,Australia)

机构地区：[1]Science,Math and Technology,Singapore University of Technology and Design,Singapore [2]School of Energy and Chemical Engineering,Xiamen University Malaysia,Selangor Darul Ehsan 43900,Malaysia [3]College of Chemistry and Chemical Engineering,Xiamen University,Xiamen 361005,China [4]School of Physics,University of Wollongong,Northfields Avenue,New South Wales 2522,Australia

出　　处：《Chinese Physics B》2020年第7期128-134,共7页中国物理B（英文版）

基　　金：Project supported by Singapore Ministry of Education(MOE)Tier 2 Grant No.(2018-T2-1-007);USA ONRG Grant No.(N62909-19-1-2047);JL is supported by MOE PhD RSS.KJAO acknowledges the funding support of Xiamen University Malaysia Research Fund,Grant Nos.XMUMRF/2019-C3/IECE/0003 and XMUMRF/2020-C5/IENG/0025;the Ministry of Higher Education Malaysia under the Fundamental Research Grant No.Scheme,Grant No.FRGS/1/2019/TK08/XMU/02;CZ acknowledges the funding support by the Australian Research Council(Grant No.DP160101474).

摘　　要：Prototypical three-dimensional(3D)topological Dirac semimetals(DSMs),such as Cd3As2 and Na3Bi,contain electrons that obey a linear momentum-energy dispersion with different Fermi velocities along the three orthogonal momentum dimensions.Despite being extensively studied in recent years,the inherent Fermi velocity anisotropy has often been neglected in the theoretical and numerical studies of 3D DSMs.Although this omission does not qualitatively alter the physics of light-driven massless quasiparticles in 3D DSMs,it does quantitatively change the optical coefficients which can lead to nontrivial implications in terms of nanophotonics and plasmonics applications.Here we study the linear optical response of 3D DSMs for general Fermi velocity values along each direction.Although the signature conductivity-frequency scaling,σ(ω)∝ω,of 3D Dirac fermion is well-protected from the Fermi velocity anisotropy,the linear optical response exhibits strong linear dichroism as captured by the universal extinction ratio scaling law,Λi j=(vi/v j)^2(where i=j denotes the three spatial coordinates x,y,z,and vi is the i-direction Fermi velocity),which is independent of frequency,temperature,doping,and carrier scattering lifetime.For Cd3As2 and Na3Bi3,an exceptionally strong extinction ratio larger than 15 and covering a broad terahertz window is revealed.Our findings shed new light on the role of Fermi velocity anisotropy in the optical response of Dirac semimetals and open up novel polarization-sensitive functionalities,such as photodetection and light modulation.

关 键 词：topological Dirac semimetal optical anisotropy linear dichroismn linear response theory 

分 类 号：O469[理学—凝聚态物理]