中国物理B ›› 2020, Vol. 29 ›› Issue (7): 77802-077802.doi: 10.1088/1674-1056/ab928e

所属专题: SPECIAL TOPIC —Terahertz physics

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

J Lim(林镇杰), K J A Ooi(黄健安), C Zhang(涨潮), L K Ang(洪礼祺), Yee Sin Ang(洪逸欣)   

  1. 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
  • 收稿日期:2020-04-15 修回日期:2020-05-07 出版日期:2020-07-05 发布日期:2020-07-05
  • 通讯作者: L K Ang, Yee Sin Ang E-mail:ricky_ang@sutd.edu.sg;yeesin_ang@sutd.edu.sg
  • 基金资助:
    Project supported by Singapore Ministry of Education (MOE) Tier 2 Grant No. (2018-T2-1-007) and 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, and 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).

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

J Lim(林镇杰)1, K J A Ooi(黄健安)2,3, C Zhang(涨潮)4, L K Ang(洪礼祺)1, Yee Sin Ang(洪逸欣)4   

  1. 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
  • Received:2020-04-15 Revised:2020-05-07 Online:2020-07-05 Published:2020-07-05
  • Contact: L K Ang, Yee Sin Ang E-mail:ricky_ang@sutd.edu.sg;yeesin_ang@sutd.edu.sg
  • Supported by:
    Project supported by Singapore Ministry of Education (MOE) Tier 2 Grant No. (2018-T2-1-007) and 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, and 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, Λij = (vi/vj)2 (where ij 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

Abstract: 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, Λij = (vi/vj)2 (where ij 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.

Key words: topological Dirac semimetal, optical anisotropy, linear dichroismn, linear response theory

中图分类号:  (Optical properties of bulk materials and thin films)

  • 78.20.-e
78.20.Bh (Theory, models, and numerical simulation) 78.20.Ci (Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity))