Quantized Nonlinear Transport with Ultracold Atoms

TL;DR

This paper proposes a method to measure quantized nonlinear transport in ultracold atomic Fermi gases, linking the response to topological properties and addressing experimental challenges for observing quantization.

Contribution

It introduces a novel scheme for quantized nonlinear transport measurement in ultracold atoms and suggests a symmetry-based averaging technique to mitigate experimental deviations.

Findings

Quantized nonlinear density response linked to Euler characteristic.

Averaging measurements reduces deviations from ideal quantization.

Method feasible with current ultracold atom experimental setups.

Abstract

In this letter, we propose how to measure the quantized nonlinear transport using two-dimensional ultracold atomic Fermi gases in a harmonic trap. This scheme requires successively applying two optical pulses in the left and lower half-planes and then measuring the number of extra atoms in the first quadrant. In ideal situations, this nonlinear density response to two successive pulses is quantized, and the quantization value probes the Euler characteristic of the local Fermi sea at the trap center. We investigate the practical effects in experiments, including finite pulse duration, finite edge width of pulses, and finite temperature, which can lead to deviation from quantization. We propose a method to reduce the deviation by averaging measurements performed at the first and third quadrants, inspired by symmetry considerations. With this method, the quantized nonlinear response can be observed reasonably well with experimental conditions readily achieved with ultracold atoms.