** This is a weekly seminar with research talks from local condensed matter theory students and postdocs, aimed at a broad quantum audience. Everyone is welcome! If you're interested in presenting at a future seminar, please send a message to This email address is being protected from spambots. You need JavaScript enabled to view it.. ** Time: Thursday, March 5 - 4:00-5:00pm Location: ATL 3100A and Virtual Via Zoom: https://umd.zoom.us/j/94978519761 Speaker:Zhi-Yuan Wei, UMD Title:Quantum dynamics of multiparty competition Abstract:Competition among multiple orders is a defining feature of strongly correlated matter, from frustrated magnets to high-Tc superconductors. Here, I will present two examples where quantum dynamics is governed by such multiparty competition.
In the first part [1], we analyze a Kondo impurity coupled to an attractive Fermi–Hubbard bath. The ground state exhibits the celebrated singlet–doublet transition. Examining transport between two one-dimensional leads connected by the impurity, we find long-time competition among charge, magnetic, and superconducting orders: a dynamical crossover from superconducting to charge-density-wave order precedes a DC current peak driven by Kondo correlations.
In the second part [2], we study one-dimensional fermions evolving under a BCS Hamiltonian with gap Δ, subject to on-site, spin-selective number measurements at rate p. Defying the common expectation that LOCC measurements cannot increase steady-state entanglement, we show that for Δ>0 the steady-state entropy S_s grows with p over a finite interval 0<p<p_th. The mechanism is a multiparty competition among unitary entanglement generation, measurement, and fermion pairing: pairing suppresses entanglement, measurement suppresses pairing, and together these effects yield a net increase in entanglement S_s as the measurement rate p rises.
Taken together, these results showcase the rich nonequilibrium phenomena that arise from multiparty competition under both unitary and monitored dynamics.