Zero-bias anomalies on Sr$_{0.88}$La$_{0.12}$CuO$_2$ thin films

TL;DR

This study investigates zero-bias anomalies in Sr$_{0.88}$La$_{0.12}$CuO$_2$ thin films, proposing two-level systems as their origin and examining how magnetic fields influence these anomalies through TLS relaxation dynamics.

Contribution

It introduces the idea that TLS relaxation rates increase in the superconducting state, affecting zero-bias anomalies and their magnetic field dependence.

Findings

Zero-bias anomalies are linked to two-level systems near the surface.

Magnetic fields weaken the TLS contribution to contact resistance.

TLS relaxation rates increase in the superconducting state, affecting anomalies.

Abstract

High-impedance contacts made on the surface of Sr$_{0.88}$La$_{0.12}$CuO$_2$ superconducting thin films systematically display a zero-bias anomaly. We consider two-level systems (TLS) as the origin of this anomaly. We observe that the contribution of some TLS to the contact resistance is weakened by a magnetic field. We show that this could result from the increase of the TLS relaxation rate in the superconducting state, due to its ability to create pairs of quasiparticles out of the condensate, when located close to the surface of the film.