NbIr$_2$B$_2$ and TaIr$_2$B$_2$ -- new low symmetry noncentrosymmetric superconductors with strong spin orbit coupling

TL;DR

This paper reports the discovery of two new noncentrosymmetric superconductors, NbIr$_2$B$_2$ and TaIr$_2$B$_2$, with high critical fields and strong spin-orbit coupling, offering a platform to explore unconventional superconductivity.

Contribution

The paper introduces two novel superconducting materials with unique crystal structures and strong spin-orbit coupling, expanding the class of noncentrosymmetric superconductors.

Findings

Superconducting transitions at 7.2 K and 5.2 K.

Critical magnetic fields exceed the Pauli limit.

First-principle calculations reveal strong spin-orbit coupling effects.

Abstract

Superconductivity was first observed more than a century ago, but the search for new superconducting materials remains a challenge. The Cooper pairs in superconductors are ideal embodiments of quantum entanglement. Thus, novel superconductors can be critical for both learning about electronic systems in condensed matter and for possible application in future quantum technologies. Here two previously unreported materials, NbIr$_2$B$_2$ and TaIr$_2$B$_2$, are presented with superconducting transitions at 7.2 and 5.2 K, respectively. They display a unique noncentrosymmetric crystal structure, and for both compounds the magnetic field that destroys the superconductivity at 0 K exceeds one of the fundamental characteristics of conventional superconductors (the Pauli limit), suggesting that the superconductivity may be unconventional. Supporting this experimentally based deduction, first-principle calculations show a spin split Fermi surface due to the presence of strong spin-orbit coupling. These materials may thus provide an excellent platform for the study of non-BCS superconductivity in intermetallic compounds.