Heat capacity double transitions in time-reversal symmetry broken superconductors

Abstract

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 multi-band 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 Sr${}_2$RuO${}_4$, 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 Sr${}_2$RuO${}_4$.

13+8 pages, 8+8 figures

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Cited by in corpus (14)

• Calorimetric evidence for two phase transitions in Ba${}_{1-\mathrm{x}}$K${}_{\mathrm{x}}$Fe${}_2$As${}_2$ with fermion pairing and quadrupling states
• Spontaneous time-reversal symmetry breaking by disorder in superconductors
• Chiral and topological superconductivity in isospin polarized multilayer graphene
• Multiband strong-coupling superconductors with spontaneously broken time-reversal symmetry
• Thermodynamic transitions and topology of spin-triplet superconductivity: Application to UTe${}_2$
• $\mu$SR measurements on Sr${}_2$RuO${}_4$ under $⟨110⟩$ uniaxial stress
• Competition between d-wave superconductivity and magnetism in uniaxially strained Sr2RuO4
• Time-reversal symmetry breaking from lattice dislocations in superconductors
• Proximity effect of time-reversal symmetry broken non-centrosymmetric superconductors
• Superconducting gap symmetry from Bogoliubov quasiparticle interference analysis on {Sr}${}_2${RuO}${}_4$
• Pair-Kondo effect: a mechanism for time-reversal broken superconductivity in UTe${}_2$
• Nonlocal electrodynamics and the penetration depth of superconducting Sr${}_2$RuO${}_4$
• Why Scanning Tunneling Microscopy on Sr${}_2$RuO${}_4$ sometimes doesn't see the superconducting gap
• Axionic $p+is$ superconductivity from two pairing channels