Low-energy excitations in type-II Weyl semimetal ${T}_{d}\text{\ensuremath{-}}{\mathrm{MoTe}}_{2}$ evidenced through optical conductivity

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Low-energy excitations in type-II Weyl semimetal $T_{d} − {MoTe}_{2}$ evidenced through optical conductivity

D. Santos-Cottin, E. Martino, F. Le Mardelé, C. Witteveen, F. O. von Rohr, C. C. Homes, Z. Rukelj, and Ana Akrap

Phys. Rev. Materials 4, 021201(R) – Published 10 February 2020

Abstract

Molybdenum ditelluride, ${MoTe}_{2}$ , is a versatile material where the topological phase can be readily tuned by manipulating the associated structural phase transition. The fine details of the band structure of ${MoTe}_{2}$ , key to understanding its topological properties, have proven difficult to disentangle experientially due to the multiband character of the material. Through experimental optical conductivity spectra, we detect two strong low-energy interband transitions. Both are linked to excitations between spin-orbit split bands. The lowest interband transition shows a strong thermal shift, pointing to a chemical potential that dramatically decreases with temperature. With the help of ab initio calculations and a simple two-band model, we give qualitative and quantitative explanations of the main features in the temperature-dependent optical spectra up to 400 meV.

Received 11 October 2019
Accepted 16 January 2020

DOI:https://doi.org/10.1103/PhysRevMaterials.4.021201

Physics Subject Headings (PhySH)

Optical conductivity Weyl fermions

Transition metal dichalcogenides Weyl semimetal

Fourier transform infrared spectroscopy Infrared spectroscopy Optical spectroscopy

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

D. Santos-Cottin^1,*, E. Martino^1,2, F. Le Mardelé¹, C. Witteveen^3,4, F. O. von Rohr^3,4, C. C. Homes⁵, Z. Rukelj^1,6, and Ana Akrap ^1,†

¹Department of Physics, University of Fribourg, 1700 Fribourg, Switzerland
²IPHYS, EPFL, CH-1015 Lausanne, Switzerland
³Department of Chemistry, University of Zürich, CH-8057 Zürich, Switzerland
⁴Physik-Institut der Universitat Zürich, CH-8057 Zürich, Switzerland
⁵Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, New York 11973, USA
⁶Department of Physics, Faculty of Science, University of Zagreb, Bijenička 32, HR-10000 Zagreb, Croatia