FIG. 1: The critical interaction strength Uc as a function of filling n is indicated by the red line. The color scale represents the relative intensity of the ferromagnetic fluctuations in the longitudinal susceptibility. In this filling region, between the two van Hove singularities nvH1 and nvH2 , strong tendencies to triplet superconductivity are predicted. The inset shows the density of states versus filling for Vso = 0 (dashed line) and Vso = 0.5 (solid line). The Fermi surface shape in each filling region is indicated.
"Topological superconductors have attracted great interest recently due to their potential use for quantum informa-tion technology and novel superconducting devices. Many interesting topological phases, such as the chiral p-wave state, are realized in superconductors with odd-parity spin-triplet pairing. However, until now only a few material systems have been discovered which show spin-triplet superconductivity, since spin-singlet pairing is in most cases the dominant pairing channel.
We study superconducting pairing instabilities of the hole-doped Rashba-Hubbard model on the square lattice with first- and second-neighbor hopping. Within the random phase approximation we compute the spin-fluctuation mediated paring interactions as a function of filling n and the local Coulomb repulsion U . Rashba spin-orbit coupling splits the spin degeneracies of the bands, which leads to two Fermi surfaces and van Hove singularities at different fillings (see Figure). We find that for a doping region in between these two van Hove fillings the spin fluctuations exhibit a strong ferromagnetic contribution (see Figure). Because of these ferromagnetic fluctuations, there is a strong tendency towards spin-triplet f -wave pairing within this filling region, resulting in a
topological nontrivial phase.
Mechanism for Unconventional Superconductivity in the Hole-Doped Rashba-Hubbard Model
Andrés Greco and Andreas P. Schnyder
Phys. Rev. Lett. 120, 177002 – Published 27 April 2018