TY - JOUR

T1 - Heat capacity double transitions in time-reversal symmetry broken superconductors

AU - Roising, Henrik S.

AU - Wagner, Glenn

AU - Roig, Merce

AU - Romer, Astrid T.

AU - Andersen, Brian M.

PY - 2022/11/29

Y1 - 2022/11/29

N2 - Standard superconductors display a ubiquitous discontinuous jump in the electronic specific heat at the critical superconducting transition temperature. In a growing class of unconventional superconductors, however, a second order parameter component may get stabilized and produce a second heat capacity jump at a lower temperature, typically associated with the spontaneous breaking of time-reversal symmetry. The splitting of the two specific heat discontinuities can be controlled by external perturbations such as chemical substitution, hydrostatic pressure, or uniaxial strain. We develop a theoretical quantitative multiband framework to determine the ratio of the heat capacity jumps, given the band structure and the order parameter momentum structure. We discuss the conditions of the gap profile which determine the amplitude of the second jump. We apply our formalism to the case of Sr2RuO4, and using the gap functions from a microscopic random phase approximation calculation, we show that recently proposed accidentally degenerate order parameters may exhibit a strongly suppressed second heat capacity jump. We discuss the origin of this result and consider also the role of spatial inhomogeneity on the specific heat. Our results provide a possible explanation of why a second heat capacity jump has so far evaded experimental detection in Sr2RuO4.

AB - Standard superconductors display a ubiquitous discontinuous jump in the electronic specific heat at the critical superconducting transition temperature. In a growing class of unconventional superconductors, however, a second order parameter component may get stabilized and produce a second heat capacity jump at a lower temperature, typically associated with the spontaneous breaking of time-reversal symmetry. The splitting of the two specific heat discontinuities can be controlled by external perturbations such as chemical substitution, hydrostatic pressure, or uniaxial strain. We develop a theoretical quantitative multiband framework to determine the ratio of the heat capacity jumps, given the band structure and the order parameter momentum structure. We discuss the conditions of the gap profile which determine the amplitude of the second jump. We apply our formalism to the case of Sr2RuO4, and using the gap functions from a microscopic random phase approximation calculation, we show that recently proposed accidentally degenerate order parameters may exhibit a strongly suppressed second heat capacity jump. We discuss the origin of this result and consider also the role of spatial inhomogeneity on the specific heat. Our results provide a possible explanation of why a second heat capacity jump has so far evaded experimental detection in Sr2RuO4.

KW - MUON SPIN RELAXATION

KW - ORDER-PARAMETER

KW - GAP STRUCTURE

KW - PHASE

KW - SR2RUO4

KW - STATE

U2 - 10.1103/PhysRevB.106.174518

DO - 10.1103/PhysRevB.106.174518

M3 - Journal article

VL - 106

JO - Physical Review B

JF - Physical Review B

SN - 2469-9950

IS - 17

M1 - 174518

ER -