Modulation spectroscopy with ultracold fermions in an optical lattice

TL;DR

This paper proposes an experimental method using modulation spectroscopy on ultracold fermions in optical lattices to measure pairing gaps and spin orderings, providing a new tool for quantum many-body physics.

Contribution

It introduces a novel modulation spectroscopy technique combined with time-dependent density-matrix renormalization group calculations to probe pairing and spin states in ultracold fermion systems.

Findings

Peak positions in the spectrum reveal pairing and interaction energies.

Spectral weight correlates with spin ordering at finite temperature.

Method effectively distinguishes superfluid and Mott-insulating states.

Abstract

We propose an experimental setup of ultracold fermions in an optical lattice to determine the pairing gap in a superfluid state and the spin ordering in a Mott-insulating state. The idea is to apply a periodic modulation of the lattice potential and to use the thereby induced double occupancy to probe the system. We show by full time-dependent calculation using the adaptive time dependent density-matrix renormalization group method that the position of the peak in the spectrum of the induced double occupancy gives the pairing energy in a superfluid and the interaction energy in a Mott-insulator, respectively. In the Mott-insulator we relate the spectral weight of the peak to the spin ordering at finite temperature using perturbative calculations.