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Rodriguez D, Tsirlin AA, Biesner T, Ueno T, Takahashi T, Kobayashi K, Dressel M, Uykur E. Two Linear Regimes in Optical Conductivity of a Type-I Weyl Semimetal: The Case of Elemental Tellurium. Phys Rev Lett 2020; 124:136402. [PMID: 32302162 DOI: 10.1103/physrevlett.124.136402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2019] [Revised: 02/07/2020] [Accepted: 03/03/2020] [Indexed: 06/11/2023]
Abstract
Employing high-pressure infrared spectroscopy we unveil the Weyl semimetal phase of elemental Te and its topological properties. The linear frequency dependence of the optical conductivity provides clear evidence for metallization of trigonal tellurium (Te-I) and the linear band dispersion above 3.0 GPa. This semimetallic Weyl phase can be tuned by increasing pressure further: a kink separates two linear regimes in the optical conductivity (at 3.7 GPa), a signature proposed for Type-II Weyl semimetals with tilted cones; this however reveals a different origin in trigonal tellurium. Our density-functional calculations do not reveal any significant tilting and suggest that Te-I remains in the Type-I Weyl phase, but with two valence bands in the vicinity of the Fermi level. Their interplay gives rise to the peculiar optical conductivity behavior with more than one linear regime. Pressure above 4.3 GPa stabilizes the more complex Te-II and Te-III polymorphs, which are robust metals.
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Affiliation(s)
- Diego Rodriguez
- 1. Physikalisches Institut, Universität Stuttgart, 70569 Stuttgart, Germany
| | - Alexander A Tsirlin
- Experimental Physics VI, Center for Electronic Correlations and Magnetism, Augsburg University, 86159 Augsburg, Germany
| | - Tobias Biesner
- 1. Physikalisches Institut, Universität Stuttgart, 70569 Stuttgart, Germany
| | - Teppei Ueno
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
| | - Takeshi Takahashi
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
| | - Kaya Kobayashi
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
| | - Martin Dressel
- 1. Physikalisches Institut, Universität Stuttgart, 70569 Stuttgart, Germany
| | - Ece Uykur
- 1. Physikalisches Institut, Universität Stuttgart, 70569 Stuttgart, Germany
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Chong H, Xu Z, Wang Z, Yu J, Biesner T, Dressel M, Wu L, Li Q, Ye H. CMOS-Compatible Antimony-Doped Germanium Epilayers for Mid-Infrared Low-Loss High-Plasma-Frequency Plasmonics. ACS Appl Mater Interfaces 2019; 11:19647-19653. [PMID: 31055915 DOI: 10.1021/acsami.9b04391] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Antimony (Sb) heavily-doped germanium (Ge)-on-silicon (Si) epitaxial films are investigated as mid-infrared (MIR) plasmonic materials. Structural, electrical, and optical properties have been improved by proper choice of dopant species (i.e., Sb) and optimization of the growth parameters (i.e., Sb flux and substrate temperature). The increased electron conductivity can be attributed to the elevated carrier concentration (1.5 × 1020 cm-3) and carrier mobility (224 cm2 V-1 s-1) in the Sb-doped Ge epilayers. The measured MIR reflectivities of the Sb-doped Ge films show free-carrier-dependent properties, which leads to tunable real and imaginary parts of permittivities. Localized surface plasmon polaritons of the bowtie antennas fabricated from the Sb-doped Ge films are demonstrated. The fabricated antennas can provide signal enhancement for the molecular vibrational spectroscopy when these vibrational lines are spectrally in proximity to the localized plasmon resonance. These CMOS-compatible Sb-doped Ge epilayers offer a platform to study the interaction of MIR plasmon with nanostructures on chips.
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Affiliation(s)
- Haining Chong
- State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering , Zhejiang University , Hangzhou 310027 , China
| | - Zemin Xu
- State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering , Zhejiang University , Hangzhou 310027 , China
| | - Zhewei Wang
- State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering , Zhejiang University , Hangzhou 310027 , China
| | - Jianbo Yu
- State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering , Zhejiang University , Hangzhou 310027 , China
| | - Tobias Biesner
- Physikalisches Institut , Universität Stuttgart , Pfaffenwaldring 57 , 70550 Stuttgart , Germany
| | - Martin Dressel
- Physikalisches Institut , Universität Stuttgart , Pfaffenwaldring 57 , 70550 Stuttgart , Germany
| | - Lan Wu
- State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering , Zhejiang University , Hangzhou 310027 , China
| | - Qiang Li
- State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering , Zhejiang University , Hangzhou 310027 , China
| | - Hui Ye
- State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering , Zhejiang University , Hangzhou 310027 , China
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