Spectroscopy for cold atom gases in periodically phase-modulated optical lattices

TL;DR

This paper explores how phase modulation of optical lattices can be used to probe the conductivity and response of cold atom gases, providing a new spectroscopic method for studying their properties.

Contribution

It introduces a theoretical framework linking phase modulation to measurable response functions, enabling direct access to conductivity in cold atom gases.

Findings

Phase modulation probes conductivity via energy absorption and double occupancy.

Application example with one-dimensional bosons at zero temperature.

Links between phase- and amplitude-modulation are discussed.

Abstract

The response of cold atom gases to small periodic phase modulation of an optical lattice is discussed. For bosonic gases, the energy absorption rate is given, within linear response theory, by imaginary part of the current correlation function. For fermionic gases in a strong lattice potential, the same correlation function can be probed via the production rate double occupancy. The phase modulation gives thus direct access to the conductivity of the system, as function of the modulation frequency. We give an example of application in the case of one dimensional bosons at zero temperature and discuss the link between the phase- and amplitude-modulation.