Fermions and bosons in nonsymmorphic PdSb2 with sixfold degeneracy
PdSb2 is a candidate for hosting sixfold-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 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  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 π, 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 Tcmax∼2.9K. We argue that the formation of Cooper pairs (bosons) is the consequence of the redistribution of the sixfold-degenerate fermions under pressure.
Publication Source (Journal or Book title)
Physical Review B
Chapai, R., Jia, Y., Shelton, W., Nepal, R., Saghayezhian, M., Ditusa, J., Plummer, E., Jin, C., & Jin, R. (2019). Fermions and bosons in nonsymmorphic PdSb2 with sixfold degeneracy. Physical Review B, 99 (16) https://doi.org/10.1103/PhysRevB.99.161110