Berezinskii-Kosterlitz-Thouless Transition in Heavy Fermion Superlattices

TL;DR

This paper explains the superconducting transitions in heavy fermion superlattices as Berezinskii-Kosterlitz-Thouless transitions, highlighting the role of effective mass mismatch and magnetic fluctuations in enabling quasi-2D superconductivity.

Contribution

It introduces a BKT transition framework for heavy fermion superlattices and analyzes the effects of magnetic fluctuations and interface pair breaking on superconductivity.

Findings

Resistivity data aligns with BKT transition signatures.

Magnetic fluctuations reduce vortex core energy near quantum critical points.

Layer reduction leads to pair breaking effects at interfaces.

Abstract

We propose an explanation of the superconducting transitions discovered in the heavy fermion superlattices by Mizukami et al. (Nature Physics 7, 849 (2011)) in terms of Berezinskii-Kosterlitz-Thouless transition. We observe that the effective mass mismatch between the heavy fermion superconductor and the normal metal regions provides an effective barrier that enables quasi 2D superconductivity in such systems. We show that the resistivity data, both with and without magnetic field, are consistent with BKT transition. Furthermore, we study the influence of a nearby magnetic quantum critical point on the vortex system, and find that the vortex core energy can be significantly reduced due to magnetic fluctuations. Further reduction of the gap with decreasing number of layers is understood as a result of pair breaking effect of Yb ions at the interface.