摘要

Cluster Mott insulator (CMI) is a new class of physical systems where the electrons are localized in the cluster units instead of lattice sites. These cluster units build the lattice. Due to the sub-Mott-gap charge fluctuation in CMIs, the idea of cluster localization leads to an emergent gauge structure at low energies.

I will present recent theoretical work on cluster Mott insulators (CMI) in which the physics of emergent lattices, charge fractionalization and quantum spin liquids can be realized. I apply the theory to explain the puzzling experiments in real materials.

For the two-dimensional anisotropic Kagome system like LiZn2Mo3O8, two distinct CMIs, type-I and type-II, arising from the repulsive interactions, are identified. In type-I CMI, the electrons are localized in one half of the triangle clusters of the Kagome system while the electrons in the type-II CMI are localized in every triangle cluster. Both CMIs are U(1) quantum spin liquids (QSL) with a spinon Fermi surface. In type-II CMI, however, the charge fluctuations give rise to local charge resonant valence bond (RVB) state that breaks the lattice symmetry. The spin degrees of freedom are immediately influenced, which gives the fractional spin susceptibility that is observed in LiZn2Mo3O8.  For the three-dimensional cluster Mott insulator, the system can further support a charge fractionalization with an emergent gauge photon in the charge sector in addition to the spin fractionalization in the spin sector. 

报告人简介

2004 graduate from University of Science and Technology of China with highest honor

2004-2010 doing PhD in Univ of California Santa Barbara with Prof Leon Balents of Kavli institute for theoretical physics

2010-2013, Postdoctoral Fellow at Univ of Colorado Boulder with Michael Hermele, Leo Radzihovsky, Ana Maria Rey

2013/10-Now Postdoctoral Fellow at Univ of Toronto.