Spin-orbit coupling controlling the superconducting dome of artificial superlattices of quantum wells

TL;DR

This paper demonstrates how spin-orbit coupling, specifically Rashba SOC, can be used to control the superconducting transition temperature in artificial quantum well superlattices, revealing a new pathway for designing high-temperature superconductors.

Contribution

First-principles calculations showing the interplay of Rashba spin-orbit coupling and phonon-mediated pairing in quantum well heterostructures to tune superconductivity.

Findings

Superconducting Tc can be tuned by Rashba SOC and quantum size effects.

Superconducting domes depend on Lifshitz transition parameters.

Quantum size effects induce two-gap superconductivity.

Abstract

While it is known that a resonant amplification of Tc in two-gap superconductors can be driven by using the Fano-Feshbach resonance tuning the chemical potential near a Lifshitz transition, little is known on tuning the Tc resonance by cooperative interplay of the Rashba spin-orbit coupling (RSOC) joint with phonon mediated (e-ph) pairing at selected k-space spots. Here we present first-principles quantum calculation of superconductivity in an artificial heterostructure of metallic quantum wells with 3 nm period where quantum size effects give two-gap superconductivity with RSOC controlled by the internal electric field at the interface between the nanoscale metallic layers intercalated by insulating spacer layers. The key results of this work show that fundamental quantum mechanics effects including RSCO at the nanoscale (Mazziotti et al Phys. Rev. B, 103, 024523, 2021) provide key tools in applied physics for quantitative material design of unconventional high temperature superconductors at ambient pressure. We discuss the superconducting domes where Tc is a function of either the Lifshitz parameter (?) measuring the distance from the topological Lifshitz transition for the appearing of a new small Fermi surface due to quantum size effects with finite spin-orbit coupling and the variable e-ph coupling g in the appearing second Fermi surface linked with the softening of the phonon energy cut off.