Electron confinement and long-range interactions in 1-D atom chains

Niek. M. M. Aarts, Anna M. H. Krieg, Emil Sierda +8 more

Solid-state quantum simulation is a powerful approach in which the material properties of a tunable platform are used to emulate user-defined model Hamiltonians. One of the biggest challenges in materials-based quantum simulation is understanding how to exactly map material-specific changes onto model parameters in a given Hamiltonian. Here, we study the electronic structure resulting from tailored quasi-1D atomic Cs chains constructed atom by atom, using scanning tunneling microscopy and spectroscopy with the aim to uncover how Cs adatoms on InSb can be used for quantum simulation. We study the dependence of the Cs-induced confined electronic states as a function of various parameters of the chain structure. We find that the lowest-level states can be well described by a 1D confinement potential, determined by the chain length, and that the critical parameter determining the depth of the attractive potential is the Cs density. We relate the observations to a lattice model Hamiltonian with exponential long-range hopping, and compare the calculated local density of states with the experimental observations, which reproduce the lowest energy states well. We find deviations from the 1D-confinement potential description for the higher-energy states, which we detail and speculate on its origin. These studies are critical for developing this material platform toward quantum simulation of electronic structure.

T. Shirai, Hideaki Kasai, Wilson Agerico Diño +2 more

Seiji Yunoki, Sadamichi Maekawa

Xing-Dong Zhao, Zhengwei Xie, Weiping Zhang

The modulational instability of coherently excited spin waves is studied in an atomic spin chain of spinor Bose-Einstein condensates (BECs) confined in an optical lattice. We examine the dependence of the stability on the long-range nonlinear interaction of spin waves excited at different lattice sites. The long-range nonlinear spin coupling in the optical lattice is due to light-induced and static magnetic dipole-dipole interaction between atoms. We compare the spin wave dynamics in an atomic spin chain of spinor BECs formed in an optical lattice with that in a Heisenberg-like spin chain in solid-state physics. This reveals the important differences of the spin chain with long-range spin coupling from that with the short-range one.

Norio Kawakami

Arindam Mallick, Jakub Zakrzewski

Quantum simulators of lattice gauge theories involve dynamics of typically short-ranged interacting particles and dynamical fields. Elimination of the latter via Gauss law leads to infinite range interactions as exemplified by the Schwinger model in a staggered formalism. This motivates the study of long-range interactions, not necessarily diminishing with the distance. Here we consider localization properties of a spin chain with interaction strength growing linearly along the chain as for the Schwinger model. We generalize the problem to models with different interaction ranges. Using exact diagonalization we find the participation ratio of all eigenstates, which allows us to quantify the localization volume in Hilbert space. Surprisingly, the localization volume changes nonmonotonically with the interaction range. Our study is relevant for quantum simulators of lattice gauge theories implemented in state-of-the-art cold atom/ion devices, and it could help to reveal hidden features in disorder-free confinement phenomena in long-range interacting systems.