Spin-obit coupling in optical superlattices

Abstract

Quantum simulation is emerging as an exciting and active frontier in atomic physics. It allows us not only to verify existing models with high precision, but also to engineer novel systems with strong correlations and exotic topologies. Recent efforts have been made to include synthetic gauge fields and spin-orbit couplings into ultracold quantum gas experiments, which would enable us to study the quantum Hall effect, topological insulators as well as topological superfluids. This thesis will describe the experimental implementation of a new spin-orbit coupled system using pseudospin-1/2 in an optical superlattices, as well as progress towards detecting the stripe phase in this system. The first part of this thesis describes the development of a new apparatus for performing quantum simulations with sodium and lithium in optical lattices. A quantum simulation program is challenging itself, therefore having a stable platform for preparing quantum gases is essential for this task. We'll describe our development in reliable and efficient production of sodium Bose-Einstein condensates and lithium degenerate Fermi gases, as well as the characterization of our optical lattice system in a superfluid to a Mott-insulator quantum phase transition. The dynamics of a Bloch oscillation in a tilted lattice has also been studied as an important step towards the implementation of synthetic magnetic fields in our system. The second part of this thesis describes the experimental realization of spin-orbit coupling in a pseudospin-1/2 system using an optical superlattice. This new scheme uses orbital states in a tilted double-well as the pseudospins, therefore does not require near-resonant Raman light to flip the spins and promise longer lifetimes compared to earlier spin-orbit coupling experiments in atomic gases. It also features a robust miscible ground state with stationary density stripes, which is closely related to the concept of supersolidity in condensed matter systems. We'll present our experimental implementation of this new system, signatures of the resonant spin-orbit coupling, as well as progress toward experimental detection of the stripe phase via Bragg scattering. This pseudospin-1/2 system could also be used for simulating quantum magnetism,and potentially novel models with topological properties and Majorana excitations.