Fermions and bosons in nonsymmorphic PdSb2 with sixfold degeneracy

TL;DR

This study investigates the exotic fermions and bosons in PdSb2, revealing its nontrivial band structure, large magnetoresistance, quantum oscillations, and pressure-induced superconductivity, highlighting its potential for hosting novel quasiparticles.

Contribution

It provides the first detailed experimental characterization of PdSb2's electronic properties and demonstrates pressure-induced superconductivity linked to its sixfold degeneracy.

Findings

PdSb2 exhibits large magnetoresistance up to 14 T.

Quantum oscillations reveal a nearly zero effective mass and nontrivial Berry phase.

Superconductivity emerges under pressure with a maximum Tc of 2.9 K.

Abstract

PdSb2 is a candidate for hosting 6-fold-degenerate exotic fermions (beyond Dirac and Weyl fermions).The nontrivial band crossing protected by the nonsymmorphic symmetry plays a crucial role in physical properties. We have grown high-quality single crystals of PdSb2 and characterized their physical properties under several stimuli (temperature, magnetic field, and pressure). While it is a diamagnetic Fermi-liquid metal under ambient pressure, PdSb2 exhibits a large magnetoresistance with continuous increase up to 14 T, which follows the Kohler's scaling law at all temperatures. This implies one-band electrical transport, although multiple bands are predicted by first principles calculations. By applying magnetic field along the [111] direction, de Haas-van Alphen oscillations are observed with frequency of 102 T. The effective mass is nearly zero (0.045m0) with the Berry phase close to {\pi}, confirming that the band close to the R point has a nontrivial character. Under quasihydrostatic pressure (p), evidence for superconductivity is observed in the resistivity below the critical temperature Tc. The dome-shaped Tc versus p is obtained with maximum Tc~2.9 K. We argue that the formation of Cooper pairs (bosons) is the consequence of the redistribution of the 6-fold-degenerate fermions under pressure.