Realization of a Cross-Linked Chiral Ladder with Neutral Fermions in a 1D Optical Lattice by Orbital-Momentum Coupling

Abstract

We report the experimental realization of a cross-linked chiral ladder with ultracold fermionic atoms in an optical lattice. In the ladder, the legs are formed by the orbital states of the optical lattice and the complex inter-leg links are generated by the orbital-changing Raman transitions that are driven by a moving lattice potential superimposed onto the optical lattice. The effective magnetic flux per ladder plaquette is tuned by the spatial periodicity of the moving lattice, and the chiral currents are observed from the asymmetric momentum distributions of the orbitals. The effect of the complex cross links is demonstrated in quench dynamics by measuring the momentum dependence of the inter-orbital coupling strength. We discuss the topological phase transition of the chiral ladder system for the variations of the complex cross links. +

Topological Devil’s staircase in atomic two-leg ladders

“…Their presence has been diagnosed by studying the behavior of the density profile, when an extra particle is put in the system with respect to the filling ν=1/2. Our results are immediately testable in cold atom experiments described by the setup in [31,32]: while the single particle Hamiltonian has already been realized, a key requirement is to reach density regimes where an incompressible phase is stabilized in the center of the harmonic trap. Given that fractional phases appear already for quarter-filled band, we expect signal-to-noise not to constitute a problem.…”

“…In the context of one-dimensional (1D) systems, ladders pierced by synthetic gauge fields [13][14][15][16][17][18][19][20][21][22][23] have been experimentally shown to display a plethora of phenomena, including chiral currents [24] and edge modes akin to the two-dimensional Hall effect [7], accompanied with the long-predicted-but hard to directly observeskipping orbits [25,26]. While such phenomena have required relatively simple microscopic Hamiltonians apt to describe electrons in a magnetic field [27], the flexibility demonstrated in very recent settings utilizing alkaline-earth-like atoms [28][29][30][31][32][33] has shown how a new class of model Hamiltonians-where nearest neighbor couplings on multi-leg ladders can be engineered almost independently one from the other-is well within experimental reach. Remarkably, these works have not only demonstrated the capability of realizing spin-orbit couplings utilizing clock transitions [29,30], but also the observation of band structures where topology is tied to inversion symmetry [31,34], a playground for crystalline topological insulators [35][36][37].…”

Creutz ladder in a resonantly shaken 1D optical lattice

“…Ultracold atoms in optical lattices, featuring tunneling amplitude engineering and tunable interaction strength, provide a unique platform for realizing and exploring such exotic topological states [3,4]. Along with the steady development of experimental techniques, many topological model systems have been recently realized, which include the Harper-Hofstadter Hamiltonian in 2D rectangular lattices [5,6], the Haldane model in a 2D hexagonal lattice [7], and various Hall and topological ladder systems based on additional synthetic dimensions such as internal atomic states [8][9][10][11][12][13] and lattice orbital states [14].…”

Nonlinear gap modes and compactons in a lattice model for spin-orbit coupled exciton-polaritons in zigzag chains

“…Finally, we note also the recent realizations of zigzag chains with large tunability for atomic Bose-Einstein condensates [36], opening up the possibility for studying related phenomena involving spin-orbit coupling in a different context. Having in mind experimental progress on coherent transfer of atomic Bose-Einstein condensates into the flat bands originating from different optical lattice configurations (e.g., [37,38]), as well as in engineering spin-orbit coupling within ultracold atomic systems [39,40], experimental realization of phenomena analogous to those described in the present work should be expected to be within reach. Very recently, a theoretical proposal for observing flat bands and compact modes for spin-orbit coupled atomic Bose-Einstein condensates in one-dimensional shaking optical lattices also appeared, where an exact tuning of the spin-orbit term could be achieved by an additional time-periodic modulation of the Zeeman field [41].…”