Bath-induced phase transitions at strong system-bath coupling: A non-perturbative mapping approach

In this talk, we introduce the Reaction-Coordinate Polaron-Transform (RCPT) approach, a non-perturbative analytic mapping framework [1] that identifies the equilibrium steady state of quantum systems strongly coupled to bosonic baths. We then apply this approach to dissipative spin chain models [2] and a dissipative fermionic model [3]. In the first example, we demonstrate that dissipative processes drive magnetic orders in spin chains. Using the RCPT framework, we show how these orders can be controlled by tuning bath locality, revealing effects such as spin splitting suppression, bath dressing, and non-local ferromagnetic interactions. In the second example, we show that coupling the Su-Schrieffer-Heeger chain to local thermal environments can alter the topological window. The RCPT framework explains how intracell or intercell coupling expands the topological-insulator or the band-insulator parameter space at the Hamiltonian level.

[1] N. Anto-Sztrikacs, A. Nazir, and D. Segal, PRX Quantum 4, 020307 (2023).

[2] BM, N. Anto-Sztrikacs, M. Brenes, and D. Segal, Phys. Rev. Lett. 132, 266701(2024).

[3] BM, K. Agarwal, and D. Segal, Phys. Rev. B. 110, 125415 (2024).