Time-reversal symmetry breaking and d-wave superconductivity of triple-point fermions

We study the possibility of complex tensor (d-wave) superconducting order in three-dimensional semimetals with chiral spin-1/2 triple-point fermions, which have an effective orbital angular momentum of L = 1 arising from a crossing of three bands. Retaining the first three lowest order terms in momentum and assuming rotational symmetry we show that the resulting mean-field d-wave ground state breaks time-reversal symmetry, but then depends crucially on the coefficients of the two quadratic terms in the Hamiltonian. The phase diagram at a finite chemical potential displays both the cyclic and the ferromagnetic superconducting states, distinguished by the average value of the magnetization; in the former state it is minimal (zero), whereas in the latter it is maximal (two). In both states we find mini Bogoliubov-Fermi surfaces in the quasiparticle spectrum, conforming to recent general arguments.

Automated summary

The study examines the possibility of complex tensor (d-wave) superconducting order in three-dimensional semimetals with chiral spin-1/2 triple-point fermions. By retaining the first three lowest order terms in momentum and assuming rotational symmetry, the resulting mean-field d-wave ground state was found to break time-reversal symmetry, depending crucially on the coefficients of the two quadratic terms in the Hamiltonian. The phase diagram at a finite chemical potential exhibits both cyclic and ferromagnetic superconducting states, distinguished by the average value of the magnetization.