Spectral weight redistribution and an indirect band gap mott insulator in a shaken optical lattice

Abstract

In this work, we explore the influence of shaking parameters on the single-particle excitation spectra of bosonic atoms confined in a one-dimensional shaken optical lattice. Using mean-field theory to solve the two-band Bose-Hubbard model, we obtain a phase diagram that qualitatively aligns with experimental observations. We employ the Random Phase Approximation (RPA) based on mean-field states to examine excitation spectra across different phases during the phase transitions. Notably, the gapless superfluid (SF) and Pi-SF phases exhibit roton-maxon excitations, whereas the gapped Mott insulator (MI) phase can manifest as a direct or indirect band-gap MI. These calculations provide detailed insights into how excitations evolve across different phases and how spectral weights areredistributed during the transitions.