Agenda

Next Quantum Materials Seminar/LANEF:

Thursday, September 14th 2023 at 2:00 pm

Julie Karel (Monash University, Clayton, Australia)

“Topology and Disordered Materials ”

To access this seminar:

Institut Néel CNRS, Building K, Room Rémy Lemaire  (K223)

Abstract: The consideration of topology has led to the emergence of new exotic physics; topological insulators and Weyl semimetals, for instance, are two classes of materials where unique properties arise due to the topology of the electronic band structure. Recent theoretical studies suggest topological effects may even be present in amorphous materials. In this talk, I will discuss experimental results probing electronic and spin transport in numerous disordered material systems. First, it will be shown that introducing disorder via porosity in the topological insulator Bi2Te3 remarkably leads to an enhanced phase coherence length and more metallic-like electronic transport behavior. Secondly, spin current generation using amorphous ferromagnetic and non-magnetic materials will be discussed. It will be shown that the anomalous Hall conductivity (σxy), when suitably normalized by magnetization and number of charge carriers, is independent of the longitudinal conductivity in a series of amorphous transition metal silicide and germanide thin films. This observation suggests a primary dependence on the intrinsic mechanism, which is remarkable because it indicates a local atomic level description of a Berry phase, resulting in an intrinsic AHE in a system that lacks lattice periodicity. The anomalous Hall angle in these systems is  found to be as large as 5%. Moreover, a very large spin orbit torque efficiency (~200%) can be realized using these amorphous materials, and the origin will be discussed. Finally, I will present our recent work patterning topological surface and edge states by inducing a transition from a crystalline to an amorphous material.

The organizers:

Elsa Lhotel (elsa.lhotel@neel.cnrs.fr)
Florence Levy-Bertrand (florence.levy-bertrand@neel.cnrs.fr)