The Vishwanath Group

We are a Theoretical Physics group specializing in the study of Condensed Matter Physics. 
We seek to understand  properties of matter such as superconductivity and magnetism  starting from fundamental physical laws like quantum mechanics.  Historically, this has led to a deeper understanding of interacting quantum systems of very many particles as well as applications like the transistor, magnetic memories and magnetic resonance imaging . 

This wordle  gives you a picture of our current interests which includes  topological phases with strong interactions, unconventional quantum critical points and and three dimensional zero-gap semiconductors (i.e. Weyl and Dirac semimetals). We explore both the fundamental theory of such states, as well as their experimental signatures. 

We use a variety of theoretical tools, e.g. quantum field theory, but our research is primarily guided by interesting physical problems and ideas rather than techniques. We are happy to pick up new tools if they suite the problem at hand - for example we recently exploited concepts from quantum information theory to sharpen our understanding of topological phases.  We also work closely with experimental groups that  study interesting states of matter in solids and ultracold atomic systems. 

Research Highlights:

1. Chiral Floquet Phases of Many-Body Localized Bosons

Key Image

Po Fidkowski, Morimoto, Potter, and Vishwanath. Phys. Rev. X 6, 041070 (2016)

Chiral topological phases feature unidirectional transport of quantities such as energy or charge around the edge. Can chiral phases exist in settings where neither charge nor energy is conserved? We find that, nonetheless, chiral phases are tenable in such systems. Instead of charge or energy, quantum information is pumped around the edges.

2. Radical chiral Floquet phases in a periodically driven Kitaev model and beyond. 

Po, Fidkowski, Vishwanath, Potter. Phys. Rev. B 96, 245116 (2017).

Figure 1

We describe a nonequilibrium topological phases in which time-periodic driving of a 2D system produces excitations with fractional statistics, and produces chiral quantum channels that propagate a quantized fractional number of qubits along the sample edge during each driving period. These phases share some common features with fractional quantum Hall states, but are sharply distinct dynamical phenomena.We construct solvable models of driven and interacting spin systems with these properties.