Probing unconventional superconductivity in inversion symmetric doped Weyl semimetal

TL;DR

This paper investigates unconventional superconducting states in doped inversion symmetric Weyl semimetals using quantum transport methods, identifying signatures of FFLO and nodal BCS states through Josephson current peaks and topological phase transitions.

Contribution

It introduces novel four-terminal measurement techniques to detect FFLO and nodal BCS states in doped Weyl semimetals, providing electrical signatures and phase diagrams.

Findings

Peak in Josephson current indicates FFLO states.

Transverse current shifts nodal points, revealing topological transitions.

Density of states decreases at quantum critical points.

Abstract

Unconventional superconductivity has been predicted to arise in the topologically non-trivial Fermi surface of doped inversion symmetric Weyl semimetals (WSM). In particular, Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) and nodal BCS states are theoretically predicted to be possible superconductor pairing states in inversion symmetric doped WSM. In an effort to resolve preferred pairing state, we theoretically study two separate four terminal quantum transport methods that each exhibit a unique electrical signature in the presence of FFLO and nodal BCS states in doped WSMs. We first introduce a Josephson junction that consists of a doped WSM and an s-wave superconductor in which we show that the application of a transverse uniform current in s-wave superconductor effectively cancels the momentum carried by FFLO states in doped WSM. From our numerical analysis, we find a peak in Josephson current amplitude at finite uniform current in s-wave superconductor that serves as an indicator of FFLO states in doped WSMs. Furthermore, we show using a four terminal measurement configuration that the nodal points may be shifted by an application of transverse uniform current in doped WSM. We analyze the topological phase transitions induced by nodal pair annihilation in non-equilibrium by constructing the phase diagram and we find a characteristic decrease in the density of states that serves as a signature of the quantum critical point in the topological phase transition, thereby identifying nodal BCS states in doped WSM.