Drastic enhancement of the superconducting temperature in type-II Weyl semimetal candidate MoTe2 via biaxial strain

Abstract

A type-II Weyl semimetal candidate MoTe2, which superconducts at Tc ∼0.1 K, is one of the promising candidates for realizing topological superconductivity. However, the exceedingly low Tc is associated with a small upper critical field (Hc2), implying a fragile superconducting phase that only exists on a small region of the H–T phase diagram. Here, we describe a simple and versatile approach based on the differential thermal expansion between dissimilar materials to subject a thin single crystalline MoTe2 to biaxial strain. With this approach, we successfully enhance the Tc of MoTe2 by fivefold and consequently expand the superconducting region on the H–T phase diagram significantly. To demonstrate the relative ease of studying the superconductivity in the biaxially strained MoTe2, we further present the magnetotransport data, enabling the study of the temperature-dependent Hc2 and the anisotropy of the superconducting state, which would otherwise be difficult to obtain in a free-standing MoTe2. Our work shows that biaxial strain is an effective knob to tune the electronic properties of MoTe2. Due to the simplicity of our methodology to apply biaxial strain, we anticipate its direct applicability to a wider class of quantum materials.