Optical conductivity of the type-II Weyl semimetal WTe2 under pressure

Abstract

Tungsten ditelluride WTe 2 is a type-II Weyl semimetal with electronic properties highly sensitive to external pressure, as demonstrated by the superconductivity emerging under pressure. Here we study the optical conductivity of the type-II Weyl semimetal WTe 2 under external pressure at room temperature. With increasing pressure, a pronounced spectral weight transfer occurs from the high-energy to the low-energy interband transitions, with drastic changes in the profile of the optical conductivity spectrum indicating a high sensitivity of the electronic band structure to external pressure. The detailed analysis of the pressure-dependent optical conductivity furthermore reveals anomalies at the pressures ∼2 and ∼4.5 GPa, where an electronic and a structural phase transition, respectively, were reported in the literature.

Probing the electronic topological transitions of WTe2 under pressure using ultrafast spectroscopy

“…The reported transition points are scattered in the pressure ranges from 4.5 to 9.6 GPa. [25,26,34,37,39] The suppression of the CP excitation of the shear mode was proposed to serve as an indicator for Td-1T' phase transition in MoTe 2 , [47] although it was not accessed yet under high pressure. Therefore, we suggest that the disappearance of the CP oscillations at 3.5 GPa marks the onset of the Td-1T' transition.…”

“…[25,26,[34][35][36][37] In addition, a Lifshitz transition also occurs at around 3 GPa, introducing a series of exotic phenomena, such as the drastic weakening of the extremely large magnetoresistance, the pronounced changes of the optical conductivity spectrum, etc. [35,38,39] Therefore, WTe 2 can serve as an ideal prototypical testbed for the investigations of pressure-induced ETT.…”