## Floquet-engineering topological Dirac bands in an optical lattice

Dr. Ian B. Spielman

Fellow, Joint Quantum Institute

National Institute of Standards and Technology and the University of Maryland

*Watch the recording*

Faculty Host: Tin-Lun (Jason) Ho

**Abstract**: Over the years my group has performed a number of experiments realizing relativistic physics using cold atoms — described by the 1D Dirac Hamiltonian in some degree of approximation. I will begin by reviewing these results in conjunction with those from the whole of the cold-atom community.

With that backdrop, I describe a spin dependent bipartite Floquet lattice, in which the dispersion relation is linear for all points in the Brillouin zone. The (stroboscopic) Floquet spectrum of our periodically-driven Hamiltonian features perfect spin-momentum locking, and a linear Dirac dispersion. These bands are protected by a Floquet topological invariant which we directly measure by using quantum state tomography.

**More about Dr. Spielman:**

Ian B. Spielman is a Fellow of the Joint Quantum Institute (JQI), a joint research institute between the National Institute of Standards and Technology (NIST) and the University of Maryland (UMd). A member of the NIST technical staff since 2006, in 2014 Spielman was appointed as a “NIST Fellow” (of NIST’s 1,800 member technical staff, just 40 are NIST fellows).

Spielman is an experimentalist in atomic, molecular and optical physics but was trained as a condensed matter physicist during his Ph.D. at Caltech from 1998 to 2004. Spielman’s research centers using ultracold-atom systems – just 10’s of nano-Kelvin above absolute zero – to realize the many-body phenomena so common in conventional materials. He has pioneered techniques to add artificial magnetic fields and spin-orbit coupling to cold-atom systems opening the door for new many-body systems. Spielman has received many awards on account of this research including the 2015 APS I.I. Rabi Prize in Atomic, Molecular, and Optical Physics.