RQMP Research Seminar

Non-conventional orders, modulation, and disentanglement in low-dimensional quantum systems

Gennady Chitov

Institut quantique & Département de physique
Université de Sherbrooke

The research to be discussed is focused on quantum phase transitions with non-conventional (topological) orders, such that the standard Landau paradigm does not work in a usual way. The main goal is to advance a new unifying theory to deal with different critical phenomena characterized by unconventional orders. The low-dimensional systems studied are mainly chains and ladders of quantum spins or fermions, with phases possessing distinct hidden orders. The latter are quantitatively described by the string or brane order parameters. The theory is advanced to calculate those quantities, along with duality transformations mapping them onto conventional local orders. Also, the winding numbers and zero-energy Majorana edge states, as additional attributes of topological order, are discussed. The modulation (i.e., appearance of oscillations in correlation functions) is related to the analytical properties of zeros of the partition functions. The latter are shown tocontain all information needed for analysis of phase transitions, of modulation transitions (disorder lines), and of the ground-state factorization (disentanglement).