Alberto Rosso (LPTMS)

Bath-Induced Phase Transitions in the XXZ Chain in a Magnetic Field

I present a study of a one-dimensional XXZ spin chain in an external magnetic field, coupled to a bath of harmonic oscillators. Using bosonization techniques, we map this dissipative quantum system onto an effective classical problem describing the thermal fluctuations of a two-dimensional interface. Within this framework, the coupling to Caldeira–Leggett baths generates effective long-range interactions in the interface representation, profoundly modifying the system’s critical properties. Using methods from statistical physics, we determine the resulting phase diagram, highlighting the competition between interactions, external magnetic field and dissipation. In particular, we show how dissipation can give rise to new phases absent in the corresponding closed system.

in collaboration with Oscar Bouverot-Dupuis and Laura Foini