Fluctuation and strain effects in a chiralp-wave superconductor

Abstract

For a tetragonal material, order parameters of px and py symmetry are related by rotation and hence have the same Tc at a mean-field level. This degeneracy can be lifted by a symmetry-breaking field, like (uniaxial) in-plane strain, such that at Tc, the order parameter is only of px or py symmetry. Only at a lower temperature also the respective other order parameter condenses to form a chiral p-wave state. At the mean-field level, the derivative of Tc with strain is discontinuous at zero strain. We analyze consequences of (thermal) fluctuations on the strain-temperature phase diagram within a Ginzburg-Landau approach. We find that the order-parameter fluctuations can drive the transition to be weakly first order, rounding off this discontinuity. We discuss the possibility of a second-order transition into a non-superconducting time-reversal-symmetry-breaking phase and consequences for the spin-triplet superconductor Sr2RuO4.

Intertwined Vestigial Order in Quantum Materials: Nematicity and Beyond

“…This simple yet robust result has important implications for the interpretation of experimental data on material candidates for p-wave superconductivity (see also Ref. [52]). The same behavior holds also for any superconducting state with a multi-component order parameter that transforms according to any of the 32 point groups of three-dimensional crystalline systems.…”

“…Particularly near a quantum phase transition, the symmetry of the order parameter is not enough to determine the final behavior of the vestigial phase, as the dynamics of the primary order parameter plays an essential role. Theoretically, while mean-field calculations are incapable of capturing vestigial phases, a variety of controlled and uncontrolled analytical methods exist, such as the saddle-point large-N approach [15,94], the self-consistent Gaussian approximation [51,52], and the renormalization-group approach [49,50]. Numerically, vestigial order can be addressed straightforwardly by analyzing the statistical properties of the corresponding higher-order correlation functions.…”

Vestigial nematic order and superconductivity in the doped topological insulator Cu x Bi2Se3

“…We determine this anisotropy from the fluctuation spectrum of the Cooper pair field. The nematic order discussed here has several parallels to spininduced Ising nematic order above a striped magnetic state of the iron-based superconductors [15][16][17][18] or to time-reversal symmetry breaking proposed for chiral superconductors in the context of SrRuO 4 , 19 , revealing the universality of the underlying principle of composite or intertwined order. 20 Before we discuss the details of our analysis we summarize the key idea of this paper.…”

Strong peak in T c of Sr 2 RuO 4 under uniaxial pressure

“…[37]. Although no cusp was seen, the resolution of that experiment does not rule out a cusp of this magnitude, and furthermore a cusp could be rounded by fluctuations [58].…”