Negative Magnetoresistance in topological crystalline insulators

Our new article on the observation and the explanation of negative magnetoresistance in PbSnSe topological crystalline insulator was highlighted among the editor’s suggestions of Physical Review Letters.

General audience summary

Topological insulators are promising materials for spintronic data processing and quantum computing. They are materials that can be made insulating in the bulk, but always conduct at the surface like metals. This is due to the fact the in such materials surface electrons have their spin coupled to their momentum. Spin transport is therefore inherent to these materials even in the absence of ferromagnetism. A second reason is the fact that one can create robust Majorana fermions using these spin-momentum locked electrons. Majoranas are potentially useful for use as qubits in quantum computers.

Up to now most studies were concerned with studying manifestations of the topological properties of these materials via their ‘exotic’ surface electrons. In our recent work, we go beyond this paradigm, and reveal manifestations of topological properties in the insulating bulk states. When materials are subjected to strong magnetic fields, their electrons are quantized into orbits, referred to as Landau orbits. In a topological material, we demonstrate that a fundamental signature from bulk electrons is an anomalous behavior of these Landau orbits, that yields a resistance that drops as a function of increasing magnetic field, contrary to what usually happens in conventional semiconductors.

With this work (Physical Review Letters 119 106606 (2017)) and our previous work on optical spectroscopy of these Landau levels (Nature partner journals, Quantum Materials 2 26 (2017)), we demonstrate bulk signatures of the topological properties of charge carriers in these materials.

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