University of Minnesota
School of Physics & Astronomy

Condensed Matter Seminar

Monday, February 22nd 2016
Speaker: Zhanybek Alpichshev, Massachusetts Institute of Technology
Subject: Non-equilibrium dynamics of a frustrated Mott insulator

A handy way to tell what‘s inside a black box is to give it a good shake. Similarly it is often a good idea to bring a system far from equilibrium to understand its inner workings.

This talk mainly focuses on the results of ultrafast optical spectroscopy on Na2IrO3, a frustrated Mott insulator with strong spin-orbit coupling. Our results indicate that there is a distinct change in the non-equilibrium behavior of excitations as the system becomes magnetically ordered at low temperatures. Specifically, we observe that in the disordered phase the transient response is due to both bound “Hubbard excitons” and unpaired single particles, whereas in the ordered phase the single particle contribution becomes strongly suppressed. This is an indication of an increase of binding energy of Hubbard excitons which we argue is due to unique interplay between the strong frustrated Kitaev term and the weak Heisenberg-type ordering term in the Hamiltonian. In this regime magnetic ordering gives rise to an effective attraction between charged excitations which grows with distance causing them to become trapped within the excitons in analogy with quark confinement inside hadrons.

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