# Electrical Step‐Edge Contact to a Topological Superconductor Candidate 2M‐WS2

## TL;DR

This paper introduces a new method to create high-quality electrical contacts to a topological superconductor, enabling the observation of its unique superconducting properties.

## Contribution

A novel step-edge contact technique is developed for encapsulated 2M-WS2, achieving ultralow contact resistance and contamination-free fabrication.

## Key findings

- The step-edge contact achieves contact resistance as low as ~65 Ω·µm for a six-unit 2M-WS2 device.
- Andreev reflection confirms highly transparent interfaces between the TSC and metal electrodes.
- Multiple anomalous resistance peaks suggest multigap superconductivity in 2M-WS2.

## Abstract

A topological superconductor (TSC), characterized by a topologically nontrivial bulk state and protected gapless boundary states, is a promising platform for hosting Majorana bound states. However, many TSCs are environmentally sensitive, especially when thinned to 2D atomic layers. This instability poses a major challenge for integrating TSCs into electronic devices. Addressing it requires full encapsulation and high‐quality electrical contact to the TSC layer, which have not yet been achieved. Here, a novel contact geometry is demonstrated for an encapsulated topological superconductor candidate, 2M‐WS2, where metal electrodes contact the exposed step‐like edges with a width of only a few nanometers. This structure yields exceptionally low contact resistance (R

C
), down to ∼ 670 Ω·µm for a single unit and ∼ 65 Ω·µm for a six‐unit 2M‐WS2 device. Below the superconducting critical temperature (T

C
), the TSC–metal interface becomes highly transparent, as evidenced by the Andreev reflection. Furthermore, the step‐edge contact prevents contamination during fabrication, enabling unprecedentedly high‐quality devices. In encapsulated 2M‐WS2, twofold rotational symmetry of the critical current (I

C
) and multiple anomalous peaks are observed in the differential resistance (dV/dI). The anisotropic I

C
originates from Fermi velocity variations along in‐plane lattice directions, while the anomalous peaks suggest multigap superconductivity in 2M‐WS2. These results reveal the intrinsic properties of 2M‐WS2 and offer a new path toward high‐performance TSC‐based electronics.

This work develops a step‐edge contact technique for encapsulated 2M‐WS2, effectively protecting the material from contamination and achieving ultralow contact resistance ( 65 µm). Highly transparent interfaces, as evidenced by Andreev reflection, enable the observation of intrinsic superconducting properties. These include twofold symmetric critical current and multiple anomalous resistance peaks, with the latter suggesting multigap superconductivity.