Measuring Zak phase in room-temperature atoms

TL;DR

This paper introduces a novel spectroscopic method to measure Zak phases in room-temperature atoms by exploiting thermal motion, enabling topological invariant detection without the need for ultra-cold conditions.

Contribution

The authors develop a technique to extract geometric Zak phases from energy spectra of superradiance lattices at room temperature, overcoming thermal noise limitations.

Findings

Zak phases measured from anti-crossings in spectra

Thermal motion acts as an effective force for spectroscopy

Method applicable to room-temperature atomic systems

Abstract

Cold atoms provide a flexible platform for synthesizing and characterizing topolog-ical matter, where geometric phases play a central role. However, cold atoms are intrinsically prone to thermal noise, which can overwhelm the topological response and hamper promised applications. On the other hand, geometric phases also de-termine the energy spectra of particles subjected to a static force, based on the po-larization relation between Wannier-Stark ladders and geometric Zak phases. By exploiting this relation, we develop a method to extract geometric phases from en-ergy spectra of room-temperature superradiance lattices, which are momentum-space lattices of timed Dicke states. In such momentum-space lattices the thermal motion of atoms, instead of being a source of noise, provides effective forces which lead to spectroscopic signatures of the Zak phases. We measure Zak phases direct-ly from the anti-crossings between Wannier-Stark ladders in the Doppler-broadened absorption spectra of superradiance lattices. Our approach paves the way of measuring topological invariants and developing their applications in room-temperature atoms.