Spectral Function of a Boson Ladder in an Artificial Gauge Field

Abstract

We calculate the spectral function of a boson ladder in an artificial magnetic field by means of analytic approaches based on bosonization and Bogoliubov theory. We discuss the evolution of the spectral function at increasing effective magnetic flux, from the Meissner to the Vortex phase, focussing on the effects of incommensurations in momentum space. At low flux, in the Meissner phase, the spectral function displays both a gapless branch and a gapped one, while at higher flux, in the Vortex phase, the spectral function displays two gapless branches and the spectral weight is shifted at a wavevector associated to the underlying vortex spatial structure, which can indicate a supersolid-like behavior. While the Bogoliubov theory, valid at weak interactions, predicts sharp delta-like features in the spectral function, at stronger interactions we find power-law broadening of the spectral functions due to quantum fluctuations as well as additional spectral weight at higher momenta due to backscattering and incommensuration effects. These features could be accessed in ultracold atom experiments using radio-frequency spectroscopy techniques.

Duality between Weak and Strong Interactions in Quantum Gases

“…Our work can be generalized in a number of ways. It can, for example, be directly extended to treat Bose-Fermi dualities in multispecies systems [52], allowing one to access cases of high experimental relevance [5][6][7][8][9][10][11][12][13]53] that up to now have been treated only in the limit of infinite repulsion [54][55][56][57], via low-energy approximations [58][59][60][61][62], or in the hydrodynamic regime [13,14,63]. Crucially, our method does not rely on integrability and allows one to study any such strongly coupled theory.…”