Probing the quantum metric of 3D topological insulators

Kavli Affiliate: Andrea D. Caviglia

| First 5 Authors: Giacomo Sala, Giacomo Sala, , ,

| Summary:

The surface states of 3D topological insulators possess geometric structures
that imprint distinctive signatures on electronic transport. A prime example is
the Berry curvature, which controls electric frequency doubling via a higher
order moment, called Berry curvature triple. In addition to the Berry
curvature, topological surface states are expected to exhibit a nontrivial
quantum metric, which plays a key role in governing nonlinear magnetotransport.
However, its manifestation has yet to be experimentally observed in 3D
topological insulators. Here, we provide evidence for a nonlinear response
activated by the quantum metric of the topological surface states of
Sb$_2$Te$_3$. We measure a time-reversal odd, nonlinear magnetoresistance that
is independent of temperature and disorder below 30 K and is thus of intrinsic
geometrical origin. Our measurements demonstrate the existence of quantum
geometry-induced transport in topological phases of matter and provide
strategies for designing novel functionalities in topological devices.

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