Ising superconductivity in the bulk incommensurate layered material (PbS)$_{1.13}$(TaS$_2$)

TL;DR

This study demonstrates Ising superconductivity and strong spin-valley locking in the bulk misfit compound (PbS)$_{1.13}$(TaS$_2$), highlighting its potential for spintronics and quantum applications.

Contribution

It provides the first comprehensive evidence of Ising superconductivity and spin-valley locking in a bulk misfit layered material, with detailed spectroscopic and magnetic measurements.

Findings

Ising superconductivity with Tc of 3.14 K

Strong spin-valley locking observed via ARPES

Absence of charge density wave signatures

Abstract

Exploiting the spin-valley degree of freedom of electrons in materials is a promising avenue for energy-efficient information storage and quantum computing. A key challenge in utilizing spin-valley polarization is the realization of spin-valley locking in bulk systems. Here, we report a comprehensive study of the noncentrosymmetric bulk misfit compound (PbS)$_{1.13}$(TaS$_2$), showing a strong spin-valley locking. Our investigation reveals Ising superconductivity with a transition temperature of 3.14 K, closely matching that of a monolayer of TaS$_2$. Notably, the absence of charge density wave (CDW) signatures in transport measurements suggests that the PbS layers primarily act as spacers between the dichalcogenide monolayers. This is further supported by angle-resolved photoemission spectroscopy (ARPES), which shows negligible interlayer coupling, a lack of dispersion along the $k_{\perp}$ direction and significant charge transfer from the PbS to the TaS$_2$ layers. Spin resolved ARPES shows strong spin-valley locking of the electronic bands. Muon spin rotation experiments conducted in the vortex phase reveal an isotropic superconducting gap. However, the temperature dependence of the upper critical field and low-temperature specific heat measurements suggest the possibility of multigap superconductivity. These findings underscore the potential of misfit compounds as robust platforms for both realizing and utilizing spin-valley locking in bulk materials, as well as exploring proximity effects in two-dimensional structures.