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R. G. Herb Condensed Matter Seminars

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Events on Thursday, April 17th, 2025

Field theory of monitored, interacting fermions with charge-conservation
Time: 10:00 am - 6:00 pm
Place: 5310 Chamberlin Hall
Speaker: Matthew Foster, Rice University
Abstract: The dynamics of entanglement in monitored quantum circuits has opened up a new chapter in far-from-equilibrium, quantum many-body physics. Charge-conserving dynamics of 1D free fermions monitored by local charge measurements are known to possess only an area-law entangled phase, with no measurement-induced phase transition (MIPT). We formulate the more interesting problem for monitored dynamics of interacting fermions, using the Keldysh formalism. We derive a simple effective statistical mechanics model for the system. We show that, as soon as local density interactions are turned on, the volume-law entangled phase and the MIPT into an area-law phase appear, the latter described by a separatrix in the weak-coupling RG flow. Invoking general symmetry principles, our theory also naturally exhibits the “charge-fuzzy” and “‘charge-sharpened” phases, as well as the “charge-sharpening” transition of KT type, identified in previous work. We explain how the simple effective stat. mech. model that we obtain is made possible by the heating effects of the measurements, which trivialize the fermion distribution function whilst still admitting a panoply of dynamical phases and transitions.
Host: Alex Levchenko
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