g-Factor Enhanced Upper Critical Field in Superconducting PdTe2 due to Quantum Confinement

TL;DR

This study demonstrates that quantum confinement in PdTe2 thin films significantly enhances the in-plane upper critical magnetic field by tuning the effective g-factor, revealing the impact of Zeeman interactions on superconductivity.

Contribution

It shows how quantum confinement can control the g-factor and thus the Pauli limit in a van der Waals superconductor, with experimental and theoretical analysis.

Findings

Hc2|| is increased by over an order of magnitude in thinner films.

Both orbital and Zeeman depairing mechanisms influence Hc2||.

Thickness-dependent g-factor affects the Pauli limit in PdTe2.

Abstract

The Pauli limiting field of superconductors determines the maximal possible value of magnetic field at which superconductivity remains possible. For weak-coupling superconductors, it is determined by an established relation that can be found by setting the condensation energy equal to the magnetization free energy. The latter is a function of the carrier g-factor. Here, we demonstrate in a van der Waals superconductor PdTe2, that quantum confinement can tune the effective g-factor causing the Pauli limit to become thickness dependent. We experimentally probe the in-plane upper critical field (Hc2||) of PdTe2 at intermediate thicknesses down to 20mK. Hc2|| is enhanced by more than an order of magnitude as the thickness is varied from 50nm down to 19nm. We model its temperature and thickness dependence, revealing that both orbital and spin Zeeman depairing mechanisms impact its value. While the variation of the orbital interaction is expected, our findings reveal how the Zeeman interaction impacts superconductivity in thin films. They aid in the search for mixed and odd pairing superconductivity where an enhancement of Hc2|| can be occasionally associated with those unconventional pairing symmetries.