Mixed singlet-triplet superconducting state within the moiré t−J−U model applied to twisted bilayer WSe2

Abstract

We analyze an analog of the t−J−U model as applied to the description of a single moiré flat band of twisted WSe2 bilayer. To take into account the correlation effects induced by a significant strength of the Coulomb repulsion, we use the Gutzwiller approach and compare it with the results obtained by the Hartree-Fock method. We discuss in detail the graduate appearance of a two-dome structure of the superconducting state in the phase diagram by systematically increasing the Coulomb repulsion integral U. The two superconducting domes residing on both sides of a Mott insulating state can be reproduced for a realistic parameter range, in agreement with the available experimental data. According to our analysis, the paired state has a highly unconventional character with a mixed d+id (singlet) and p−ip (triplet) symmetry. Both components of the mixed paired state are of comparable amplitudes. However, as shown here, a transition between pure singlet and pure triplet pairing should be possible in the considered system by tuning the top and bottom gate voltage, which controls the magnitude of valley-dependent spin splitting in the system.

Source-reported materials — not catalogue approval

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