Experimental Observation of Momentum-Space Chiral Edge Currents in Room-Temperature Atoms

Abstract

Chiral edge currents play an important role in characterizing topological matter. In atoms, they have been observed at such a low temperature that the atomic motion can be measured. Here we report the first experimental observation of chiral edge currents in atoms at room temperature. Staggered magnetic fluxes are induced by the spatial phase difference between two standing-wave light fields, which couple atoms to form a momentum-space zigzag superradiance lattice. The chiral edge currents have been measured by comparing the directional superradiant emissions of two timed Dicke states in the lattice. This work paves the way for quantum simulation of topological matter with hot atoms and facilitates the application of topological physics in real devices.

Synthesized magnetic field of a sawtooth superradiance lattice in Bose–Einstein condensates

“…This AB phase determines the moving direction of excitations created in the SL and induces nonsymmetric reflectivities when the SL is probed in two opposite directions. Compared with the lattices studied in previous work, 13,14,16,18,19 the key difference of the edge states lies in the flatband. This work is promising to study the relevant effects, including the Bloch-Zener oscillation 21 and compact localized states.…”

“…Unlike previous study of the gauge field simulation in ultracold atoms, 10,11,13,14 the band structure is characterized by optical spectra. 19 Our scheme offers the possibility to probe the band structure of SL in situ 28 without atomic time of flight (TOF) imaging. By using a short probe pulse, e.g., a π-pulse, instead of the long one in the current scheme to pump a single excitation to the SL, we can measure the dynamics of the single excitation.…”

“…The chiral current is defined as J e = ∑ i=± ∫dxδ(E i − E)|〈ψ i |e〉| 2 ∂E i ∕∂x. 19 For positive dispersion of the e j i edge, i.e., red lines in Fig. 2b, the momentum decreases with time.…”

“…17 Chiral edge currents have been observed in ultracold 13,14,16,18 and hot atoms. 19 Recently, one-dimensional superradiance lattice (1D SL) 20 of a Bose-Einstein condensate (BEC) based on standing wave-coupled electromagnetically induced transparency (EIT) was realized experimentally. 24 The band structure was investigated by measuring the directional emissions of one of the superradiant excited state in the 1D SL.…”

Many-Body Chiral Edge Currents and Sliding Phases of Atomic Spin Waves in Momentum-Space Lattice

“…When the standing wave lasers are phase mismatched [ Fig. 1(a)], a synthetic magnetic field is generated [50]. This gives a nearest-neighbor hopping with complex amplitudes along and between the ladders, described by the Hamiltonian…”