Superconducting Triple Point in UTe$_2$: Thermodynamics and Symmetry (opens in new tab)

Three lines of second-order phase transitions between the normal phase and two distinct superconducting phases meet at a single point on the phase diagram of UTe$_2$. Contrary to common belief, there are no thermodynamic constraints for such triple points. The phase diagram is interpreted within Landau theory in terms of two superconducting order parameters with different gauge symmetries. Such an interpretation is unique under the assumption of...