Upper critical field in ferromagnetic metals with triplet pairing

Abstract

The theory of triplet superconductivity in ferromagnetic metals based on electron-electron interaction by spin fluctuation exchange is developed. The equations for the upper critical field temperature dependence are derived. In contrast to the similar equations for the superconductivity in two band metals they contain the pairing amplitudes and the Fermi velocities depending on magnetic field. The critical field behaviour near the critical temperature and at T = 0 is established analytically.

Unconventional superconductivity in UTe2

“…Indeed, in the weak coupling limit, λ could be field dependent and have a strong influence on the field dependence of H c2 , with almost no noticeable effects on γ: in the weak coupling limit (λ → 0), T SC depends exponentially on λ through a BCS-like relation T SC ∝ exp − 1 λ−μ * , whereas γ ∝ (1 + λ). Moreover, for paring mediated by magnetic fluctuations, the relation between γ and λ is not as simple as for the phonon case notably in the strong coupling regime [115].…”

A review of UTe2at high magnetic fields

“…Yet this is in the context of a ferromagnetically ordered superconductor, whereas in UTe 2 there is no long-range magnetic order at ambient pressure. Rather, for UTe 2 it may be the case that the mass renormalization and the superconducting pairing each have their own magnetic field dependence [74]. As seen in figure 3, enhanced superconductivity only appears for a narrow angular range of magnetic field direction near the b axis, while the metamagnetic transition-and the accompanying enhancement of effective mass-occurs for a much broader angular range.…”

Piezomagnetism in ferromagnetic superconductors

“…At temperature decrease these substances pass to the superconducting state which reveals specific piezomagnetic qualities. The superconducting state in these ferromagnetic metals is developed at least in two (spin-up, spin-down) conducting bands and described by multicomponent order parameter [7][8][9]. In order not to overload the presentation with the corresponding cumbersome calculations, we will demonstrate the manifestation of piezomagnetism in the superconducting state using the simplest one-component model of superconductivity.…”