Current redistribution model of anomalous resistance behaviour in superconductor-topological insulator heterostructures

TL;DR

This study investigates the anomalous resistance behavior in superconductor-topological insulator heterostructures, attributing it to current redistribution effects at the interface rather than long-range superconducting proximity.

Contribution

The paper introduces a current redistribution model validated by finite element analysis to explain long-range resistance anomalies in superconductor-TI heterostructures.

Findings

Resistance anomalies are caused by current redistribution at the interface.

Long-range superconducting proximity effect is ruled out as the cause.

Finite element analysis confirms the proposed CRD model.

Abstract

Anomalous resistance upturn and downturn have been observed on the topological insulator (TI) surface in superconductor-TI (NbN-Bi1.95Sb0.05Se3) heterostructures at ~ mm length scales away from the interface. Magnetotransport measurements were performed to verify that the anomaly is caused due to the superconducting transition of the NbN layer. The possibility of long range superconducting proximity effect due to the spin-polarized TI surface state was ruled out due to the observation of similar anomaly in NbN-Au and NbN-Al heterostructures. It was discovered that the unusual resistance jumps were caused due to current redistribution at the superconductor-TI interface on account of the geometry effects. Results obtained from finite element analysis using COMSOL package has validated the proposed current redistribution (CRD) model of long range resistance anomalies in superconductor-TI and superconductor-metal heterostructures.