In 2007 he joined Microsoft's Station Q as a research physicist, on leave from the UCSB physics department.
Some of his most important works have been in the theories of quantum phase transitions, in particular superconductor-insulator transitions (with Daniel Fisher, Steven Girvin and others) and deconfined quantum criticality (with Subir Sachdev, T. Senthil, Ashvin Vishwanath and Leon Balents).
He has also made significant advances in the transport and other aspects of the physics of Luttinger liquids (with Charles Kane) and other one-dimensional problems in condensed matter such as the edges of quantum Hall states.
He has also done important works in the area of quantum spin liquids, often using the aforementioned dualities to provide theoretical descriptions of various spin liquid phenomena (with Leon Balents, Michael Hermele, Jason Alicea, Shinsei Ryu and others).
He has also made important contributions to the physics of carbon nanotubes (with Leon Balents and Charles Kane) and emergent Majorana fermions and related phenomena in quasi-one-dimensional problems (with Jason Alicea and others).