Physical properties of noncentrosymmetric tungsten and molybdenum aluminides

TL;DR

This paper reports the growth and physical characterization of noncentrosymmetric tungsten and molybdenum aluminides, highlighting their potential for unconventional physics and superconductivity due to lack of inversion symmetry.

Contribution

It presents the first single crystal growth and physical property analysis of Al$_4$W, Al$_5$W, and related molybdenum aluminides, expanding candidate materials for exotic physics.

Findings

All compounds are nonmagnetic metals with high conductivity.

Potential for superconductivity at lower temperatures due to their properties.

Limits on transition temperatures suggest possible significant parity mixing in superconductivity.

Abstract

A lack of spatial inversion symmetry gives rise to a variety of unconventional physics, from noncollinear order and Skyrmion lattice phases in magnetic materials to topologically-protected surface states in certain band insulators, to mixed-parity pairing states in superconductors. The search for exotic physics in such materials is largely limited by a lack of candidate materials, and often by difficulty in obtaining crystals. Here, we report the single crystal growth and physical properties of the noncentrosymmetric tungsten aluminide cage compounds Al$_4$W and Al$_5$W, alongside related molybdenum aluminides in which spin-orbit coupling should be significantly weaker. All compounds are nonmagnetic metals. Their high conductivities suggest the opportunity to find superconductivity at lower temperatures, while the limits we can place on their transition temperatures suggest that any superconductivity may be expected to exhibit significant parity mixing.