DEPARTMENT OF PHYSICS DISSERTATION: Zhaoyu Han

Ph.D. Candidate:  Zhaoyu Han

Date: July 10, 2024 Time: 2:00 pm

Research Advisor: Steven A. Kivelson

Location: Mccullough 335 

Zoom Link: https://stanford.zoom.us/j/96603101628?pwd=BkGOOYWPr15XbJeIbp1UWCBUCAJa69.1

Zoom Password: Email physicsstudentservices [at] stanford.edu (physicsstudentservices[at]stanford[dot]edu) for password. 

Title:  Emergent gauge fields in strongly coupled electron-phonon systems

Abstract: Resonating valence bond (RVB) states describe one of the most extreme classes of quantum phases that feature emergent gauge fields at low energy. Since this concept was revived by Anderson in 1973 in the spin physics context, the pursuits of such phases have been mostly restricted to the studies of frustrated antiferromagnets. In this talk, I will introduce an entirely different route to their possible realizations, which builds on phonon degrees of freedom on lattice bonds – roughly realizing the original intuitive depiction of RVB by Pauling in 1949. I will provide two explicit minimal models as caricatures of two types of electron-phonon systems, where it can be shown with asymptotically exact arguments that deconfined gauge fields emerge in certain strong coupling regimes of their phase diagrams. Particularly I will show that such phases can appear in electronically trivial `band insulators’ proximate to ferroelectric ordering.