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The Anthony J Leggett Institute for Condensed Matter Physics Seminar: "Unconventional discontinuous transitions in a 2D system with spin and valley degrees of freedom"

Event Type
Seminar/Symposium
Sponsor
Physics Department
Location
ESB 190
Date
Dec 2, 2024   12:00 pm  
Speaker
Andrey Chubukov, Universiy of Minnesota
Contact
Stephen Bullwinkel
E-Mail
bullwink@illinois.edu
Phone
217-333-1652
Views
51
Originating Calendar
Physics - The Anthony J Leggett Institute for Condensed Matter Theory Seminar

We analyze the transition into the most favorable ordered state for a system of 2D fermions with spin and valley degrees of freedom.  We show that for short-ranged interactions and a range of rotationally invariant dispersions, the ordering transition is highly unconventional:  the associated susceptibility diverges (or almost diverges) at the transition, yet immediately below it the system jumps discontinuously into a fully polarized state. We analyze  the dispersion of  longitudinal and transverse  collective   modes in different parameter regimes above and below the transition. Additionally, we consider ordering in a system with full SU(4) symmetry and show that there is a cascade of discontinuous transitions into a set of states, which includes a quarter-metal, a half-metal and a three-quarter metal. We compare our results with the data for biased bilayer graphene and AlAs.

 * In  collaboration with Z. Raines (UMN) and L.I. Glazman (Yale)

 

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