Surface superconductivity in the Weyl semimetal MoTe2 detected by point contact spectroscopy
Abstract
MoTe2 is a Weyl semimetal, which exhibits unique non-saturating magnetoresistance and strongly reinforced superconductivity under pressure. Here, we demonstrate that a novel mesoscopic superconductivity at ambient pressure arises on the surface of MoTe2 with a critical temperature up to 5 K significantly exceeding the bulk T c = 0.1 K. We measured the derivatives of I-V curves for hetero-contacts of MoTe2 with Ag or Cu, homo-contacts of MoTe2 as well as ‘soft’ point contacts (PCs). Large number of these hetero-contacts exhibit a dV/dI dependence, which is characteristic for Andreev reflection. It allows us to determine the superconducting gap Δ. The average gap values are 2Δ = 1.30 ± 0.15 meV with a 2Δ/k B T c ratio of 3.7 ± 0.4, which slightly exceeds the standard BCS value of 3.52. Furthermore, the temperature dependence of the gap follows a BCS-like behavior, which points to a nodeless superconducting order parameter with some strong-coupling renormalization. Remarkably, the observation of a ‘gapless-like’ single minimum in the dV/dI of ‘soft’ PCs may indicate a topological superconducting state of the MoTe2 surface as these contacts probe mainly the interface and avoid additional pressure effect. Therefore, MoTe2 might be a suitable material to study new forms of topological superconductivity.
- Publication:
-
2D Materials
- Pub Date:
- October 2018
- DOI:
- 10.1088/2053-1583/aad3e2
- arXiv:
- arXiv:1805.02470
- Bibcode:
- 2018TDM.....5d5014N
- Keywords:
-
- Condensed Matter - Superconductivity
- E-Print:
- 9 pages, 7 figures. Presented at the 6th International Conference on Superconductivity and Magnetism (ICSM2018), April 29 - May 04, 2018 (Antalya, Turkey)