# Gate-tunable negative differential conductance in hybrid semiconductor-superconductor devices

## TL;DR

This study demonstrates gate-tunable negative differential conductance in hybrid semiconductor-superconductor devices, revealing how it depends on voltage, magnetic field, and superconducting gap, advancing understanding of tunneling transport mechanisms.

## Contribution

We introduce the BTK-supercurrent model to explain gate and magnetic field effects on NDC in hybrid devices, providing new insights into their transport properties.

## Key findings

- NDC weakens and shifts with gate voltage and magnetic field.
- NDC disappears when the superconducting gap closes.
- The BTK-supercurrent model accurately explains observed behaviors.

## Abstract

Negative differential conductance (NDC) manifests as a significant characteristic of various underlying physics and transport processes in hybrid superconducting devices. In this work, we report the observation of gate-tunable NDC outside the superconducting energy gap on two types of hybrid semiconductor-superconductor devices, i.e., normal metal-superconducting nanowire-normal metal and normal metal-superconducting nanowire-superconductor devices. Specifically, we study the dependence of the NDCs on back-gate voltage and magnetic field. When the back-gate voltage decreases, these NDCs weaken and evolve into positive differential conductance dips; and meanwhile they move away from the superconducting gap towards high bias voltage, and disappear eventually. In addition, with the increase of magnetic field, the NDCs/dips follow the evolution of the superconducting gap, and disappear when the gap closes. We interpret these observations and reach a good agreement by combining the Blonder-Tinkham-Klapwijk (BTK) model and the critical supercurrent effect in the nanowire, which we call the BTK-supercurrent model. Our results provide an in-depth understanding of the tunneling transport in hybrid semiconductor-superconductor devices.

---
Source: https://tomesphere.com/paper/2303.00214