Two-dimensional bulk Fulde–Ferrell state and gapless superconducting edge modes in the 1T'-WS<sub>2</sub>/2H-WS<sub>2</sub> heterophase bilayer
ORAL
Abstract
We propose a material platform comprised of transition metal dichalcogenide (TMDC) heterostructures to realize the two-dimensional (2D) Fulde–Ferrell (FF) state and gapless superconducting edge modes. By van der Waals stacking a 2D superconductor (1T'-WS2 with inversion symmetry) on top of a 2D topological insulator (2H-WS2 with mirror symmetry), the resulting TMDC bilayer exhibits Rashba superconductivity with broken inversion symmetry. Under an external in-plane magnetic field, the system can host finite-momentum Cooper pairing, evidenced by the divergence in the particle-particle susceptibility calculated from a k · p Hamiltonian fitted to the ab initio theory band structure. The resulting bulk FF state can induce superconductivity in the edge states with its spatially varying order parameter. By varying the strength of the in-plane magnetic field, we demonstrate that the edge state can undergo a phase transition to a one-dimensional gapless phase with narrow Fermi segments corresponding to zero-energy Bogoliubov quasi-particles. The controllable one-dimensional gapless phase serves as a clear experimental fingerprint of FF state and has potential applications on nonreciprocal superconducting transport and the engineering of Majorana-based quantum devices.
*This research used Theory and Computation resources at the Center for Functional Nanomaterials (CFN), which is a U.S. Department of Energy Office of Science User Facility, at Brookhaven National Laboratory under Contract No. DE-SC0012704. Y.B. acknowledges support from the DOE EPSCoR program under the award DE-SC0022178. Y.P. acknowledges the funding support from the National Science Foundation under grant no. DMR-2143233. J.C. acknowledges support from the NSF under Grant No. DMR-1942447 and from the Flatiron Institute, a division of the Simons Foundation. This research used resources of the National Energy Research Scientific Computing Center (NERSC), a Department of Energy User Facility using NERSC award BES-ERCAP28324 and 32137.
