Natan Andrei – Rutgers University
Date/Time/Location
Thursday, February 19, 2026, 12:10 pm; Hill Center 705
Thermodynamics in a split Hilbert space: Quantum impurity in interacting environments
A rich phase diagram arises when a quantum spin impurity is placed in an interacting environment. Different phases arise depending on the relative strengths of the various interactions, in marked difference from the Kondo effect the canonical example of a spin impurity placed in a metal where only one phase prevails. We show further that in each phase the Hilbert space splits into several towers of excitations and as a result the thermodynamics requires tower summation in each phase. We compute explicitly the resulting impurity entropy in each phase and show that it exhibits interesting behavior which is experimentally verifiable and reflecting the underlying tower structure.