Superconductivity, charge density wave, and supersolidity in flat bands with tunable quantum metric

          @misc{ pirsa_PIRSA:22050039,
            doi = {10.48660/22050039},
            url = {https://pirsa.org/22050039},
            author = {Hofmann, Johannes},
            keywords = {Condensed Matter},
            language = {en},
            title = {Superconductivity, charge density wave, and supersolidity in flat bands with tunable quantum metric},
            publisher = {Perimeter Institute},
            year = {2022},
            month = {may},
            note = {PIRSA:22050039 see, \url{https://pirsa.org}}
          }
          

Abstract

Predicting the fate of an interacting system in the limit where the electronic bandwidth is quenched is often highly non-trivial. The complex interplay between interactions and quantum fluctuations driven by the band geometry can drive a competition between various ground states, such as charge density wave order and superconductivity. In this work, we study an electronic model of topologically-trivial flat bands with a continuously tunable Fubini-Study metric in the presence of on-site attraction and nearest-neighbor repulsion, using numerically exact quantum Monte Carlo simulations. By varying the electron filling and the spatial extent of the localized flat-band Wannier wavefunctions, we obtain a number of intertwined orders. These include a phase with coexisting charge density wave order and superconductivity, i.e., a supersolid. In spite of the non-perturbative nature of the problem, we identify an analytically tractable limit associated with a `small' spatial extent of the Wannier functions, and derive a low-energy effective Hamiltonian that can well describe our numerical results.