Non-Fermi Liquid Phase from Dipole Symmetry

Multipole symmetries and conservation laws are relatively new concepts in condensed matter, with their microscopic consequences and symmetry-broken phases being the subject of ongoing research. Motivated by the recent study of bosonic systems with dipolar symmetry [1], we consider fermions on a 2-D square lattice with both charge and dipole moment conservation. The model is intrinsically interacting due to the dipolar symmetry, and we explore the phase diagram of the model using mean-field methods. In particular, we find a phase where the dipolar symmetry is spontaneously broken. In this phase, fermions acquire dispersion from the condensation of dipole moments and the low-energy theory is that of a Fermi surface coupled to Goldstone modes of the broken symmetry. Moreover, we notice that the Goldstone-Fermion coupling is non-vanishing at low momentum, which gives rise to a non-Fermi liquid state at low energy in the dipole condensed phase.

[1]: Lake, et al., Phys. Rev. B 106, 064511