The Joint Condensed Matter Seminar (JCMS) series is organised by KTH Royal Insitute of Technology, Nordita, and Stockholm University.
On Monday, January 30th, 2023 from 11 am to 12 am we will host a seminar by Paolo Molignini from Stockholm University.
Topological phase transitions at finite temperature
Zero-temperature one-dimensional topological systems with inversion symmetry are described by a topological invariant known as the Zak phase. Recently, a generalisation of this quantity to open systems - known as the Ensemble Geometric Phase (EGP) - has emerged as a robust way to describe topology at non-zero temperature. By using this quantity, we explore the nature of topology allowed for dissipation described by Lindblad and Redfield master equations. We introduce two main aspects to the theory of open system topology. We discover topological phase transitions as a function of the temperature T, manifesting as changes in differences of the EGP accumulated over a closed loop in parameter space. We characterise the nature of these transitions and reveal that the corresponding non-equilibrium steady state can exhibit a nontrivial structure - contrary to previous studies where it was found to be in a fully mixed state. Additionally, we demonstrate that the EGP becomes itself a quantised quantity when key symmetries are present.