Flat-band-induced non-Fermi-liquid behavior of multicomponent fermions

Abstract

We investigate multicomponent fermions in a flat band and predict experimental signatures of non-Fermiliquid behavior. We use dynamical mean-field theory to obtain the density, double occupancy and entropy in a Lieb lattice for N = 2 and N = 4 components. We derive a mean-field scaling relation between the results for different values of N , and study its breakdown due to beyond mean-field effects. The predicted signatures occur at temperatures above the Néel temperature and persists even in the presence of a trapping potential, thus they are observable in current ultracold gas experiments.

Catalogue of Flat-Band Stoichiometric Materials

“…We refer to the sublattices formed by Ca atoms and N atoms as L and L, respectively. We introduce the S matrix formed by the s or d 2 z orbital in L and p orbitals in L as (1,2,3) corresponds to the p x , p y and p z orbitals at (0, 0, 1/2) in L. The S-matrix reads…”

“…Electrons whose energy dispersion is bound within a narrow window are conjectured to exhibit a wide-range of interesting physics phenomena. Such electrons form a high density of states "flat band", where many-body effects dominate over the kinetic energy and where Fermisurface physics gives way to strongly interacting, non-Fermi liquid behavior [2]. The archetypal such system -and until recently the only experimentally discovered one -is the Fractional Quantum Hall effect [3][4][5][6], where non-abelian quasiparticle excitations can appear under a fractional filling of an electronic flat band that develops in the presence of a large magnetic field.…”

“…1(b), where the quenching of the kinetic energy arises from interference effects despite large electron orbital overlaps and hopping. The latter type of bands can host many exotic quantum phenomena, including magnetism, fractional quantum Hall effect at zero field [3][4][5][6], unconventional superconductivity [8,15,16], non-Fermi liquid behavior [2] and anomalous Landau level beyond the Onsager's rule [17]. Such topological bands can enhance the superfluid weight in twisted bilayer graphene [18,19] and could lead to high-temperature superconductivity.…”

Kondo-lattice-mediated interactions in flat band systems

“…While a wide variety of correlated states in flat band systems can emerge, minimal attractive or repulsive on-site interactions are well known to lead to magnetism and superconductivity, respectively [2,[21][22][23][24][25][26][27]. More complex interactions in flat bands are also well known to give rise to other symmetry broken states, including charge density waves and bond orders [28][29][30][31]. The different interactions considered are usually written as an effective density-density interaction.…”

Possible insulator-pseudogap crossover in the attractive Hubbard model on the Lieb lattice

“…The normal state of (partially or nearly) flat-band systems with repulsive interactions has also been studied in Refs. [25][26][27][28][29]. We calculate the orbital-resolved pair and spin susceptibilities based on two-particle Green's functions.…”