Cancelled Interacting topological phases of matter

by Dr. Dganit Meidan

Department Of Physics, Ben-Gurion University Of The Negev
at Physics Colloquium

Tue, 17 Mar 2020, 15:30
Building 37, room 202


Topological insulators (TI) are an exotic state of quantum matter, distinct from ordinary insulators in that while their bulk cannot conduct electricity, their surface supports conducting states. TI’s provide new platforms for exploring fundamental science questions, and hold promise for a multitude of applications including the possibility to encode and manipulate quantum information in a way that is inherently protected against decoherence.
Despite immense progress in discovering, realising and employing topological phases, one prominent challenge is understand the role of e-e interactions which alter their fundamental properties resulting in a rich and complex variety of physical phenomena. The impact of interactions can be divided into two complementary actions: reducing the topological protection that stabilises these phases, and creating new topological orders in which quasi particles carry fractional charge and statistics, thus permitting a wider range of applications.
In this talk I will discuss one example of each phenomena. As a first example I will address a recent conjecture which suggests that the stability of non-abelian excitations at high energies can be enhanced due to disorder-induced localization. This notion has been called localization-protected topological-order and its consequences could be far-reaching, allowing for topological quantum processors that can be operated at high temperatures. We conduct a numerical study of the effect of disorder on the stability of the many body zero mode in a Kitaev chain with local interactions. We find that disorder can both enhance and degrade topological order. We further identify a regime of parameter space where topological superconductivity coexists together with a significant violation of Eigenstate-Thermalisation-Hypothesis.
As a second example I will discuss the topological classification of parafermionic chains in the presence of a modified time reversal symmetry. Such chains can be realized in one dimensional structures embedded in fractionalized two dimensional states of matter. I will discuss how we identify the interface Z_N parafermions and their composition for the physical problem at hand. I will then show how the different topological phases of the parafermionic chain split when time reversal symmetry is added. I will identify a composite Haldane phase and demonstrate the appearance of emergent Majorana zero modes in a system where the constituents particles are either fermions or bosons.

Created on 11-03-2020 by Bar, Ilana (ibar)
Updaded on 14-03-2020 by Bar, Ilana (ibar)