Topological nonsymmorphic metals from band inversion

Date

Feb 15, 2017

Time

2:00 PM - 3:00 PM

Language

en

Main Topic

Physik

Other Topics

Physik

Host

Lukas Muechler (Princeton University)

Description

According to the Landau-Ginzburg paradigm, different phases of matter are distinguished by their symmetry. A recent major advance led to the recognition that insulators with the same symmetries and particle numbers can be topologically distinct. That is, for the same electron filling and symmetry class, one may have either trivial or topological insulators. This scenario is substantially modified for crystals having a broad class of spatial symmetries that are commonly found in nature called nonsymmorphic symmetries. Nonsymmorphic symmetries are fundamentally different, in that they naturally lead to energy bands that stick together, which guarantees that at certain fillings the phase of matter must _always_ be gapless. Our work explores the distinct phases of matter within this broad class of spatial symmetries, but _for fillings that do not guarantee gaplessness_. We find that a topological phase transition separates a trivial, gapped phase from a topological, gapless phase. This contrasts with the conventional paradigm that a phase transition separates a trivial from a topological insulator. We show, based on ab-initio calculations and tight-binding models, that MTe2 (M = W, Mo) monolayers without spin-orbit coupling are examples of this novel topological metal. We further find that important aspects of the electronic properties of the MTe2 monolayer survive in bilayer and three-dimensional MTe2, which among other things show a record high magnetoresistance. We propose that the magnetoresitance has a unique topological origin - precisely, it originates from the topological metallicity discussed above.

Last modified: Feb 15, 2017, 8:40:33 AM