Upper critical magnetic field in superconducting Dirac semimetal

¹ Electrophysics Department, National Chiao Tung University - Hsinchu 30050, Taiwan, ROC
² Physics Department, Bar-Ilan University - 52900 Ramat-Gan, Israel
³ School of Physics, Peking University - Beijing 100871, China
⁴ Collaborative Innovation Center of Quantum Matter - Beijing, China

Received: 6 September 2018
Accepted: 15 October 2018

Abstract

Temperature dependence of the upper critical field H_c2 of the Dirac semimetal (DSM) with phonon-mediated pairing is considered within the semiclassical approximation. The low-temperature dependence deviates from conventional BCS superconductor with parabolic dispersion relation (Werthamer N. R., Helfand E. and Hohenberg P. C., Phys. Rev., 147 (1966) 295; Helfand E. and Werthamer N. R., Phys. Rev. Lett., 13 (1964) 686) even for large adiabaticity parameter, , where μ is the chemical potential and Ω the Debye frequency. In particular the “reduced field”, ratio of zero-temperature H_c2 to the derivative at critical temperature, , depends on γ and can be extended beyond the adiabatic limit. The reduced magnetic field ratio is universal (independent of the chemical potential, interaction strength, etc.) and smaller than the Werthamer ratio for clean superconductors: for DSM, for parabolic band. The results are in good agreement compared with recent experiments on TaP.