Speaker： Gyu-Boong Jo
Title：Emulating topological matter with ultracold fermions in engineered optical lattices
Abstract：
Ultracold atoms that are extremely pristine systems provide controllable platforms in emulating topological phases in optical lattices with bosonic and fermionic atoms. In this talk, we demonstrate the quantum simulation of topological phases realized in spin-orbit-coupled ultracold fermions trapped in 1D and 2D optical lattices.
First, we disucss the observation of a novel type of symmetry-protected topological (SPT) phases realized in 1D optical lattices. The observed SPT phase is beyond the Altland-Zirnbauer classification, and protected by mirror and a generalized chiral symmetry that can be manipulated in an optical lattice with Raman-induced spin-orbit coupling, with its topology being detected by measuring the spin polarization of Bloch states at highly symmetric points of the Brillouin zone. Quite interestingly, the nontrivial topology of the phase is also reflected in the non-equilibrium spin dynamics when the system is quenched from initial phase to the trivial and nontrivial phases. We demonstrate the underlying mechanisms of the spin relaxation dynamics in the present SPT phase. Secondly, we present the engineering of 2D spin-orbit coupling for ultracold fermions in optical lattices, leading to the realization of 2D Dirac-type semimetal band structure. With proper band engineering, we explore the topological phase transition between topological and trivial phases by measuring the spin polarization within the first Brillouin zone, and furthermore investigate the temperature dependence of the spin texture of the topological Bloch band in the topological semimetal band structure. Our works should pave the way for the quantum simulation of topological phases in and out of equilibrium for ultracold fermions.