Spin memory of the topological material under strong disorder

TL;DR

This study reveals that disordered topological Sb2Te3 films exhibit a robust spin response and spin memory effects at high temperatures, with disorder controlling the transition between topological and trivial states, highlighting disorder's role in spin transport.

Contribution

It demonstrates the existence of disorder-induced spin correlations and spin memory in amorphous topological materials, extending understanding of topological protection limits under strong disorder.

Findings

Robust spin response detected in amorphous Sb2Te3 films.

Spin memory phenomenon driven by localized spins in disordered state.

Transition from negative to positive magnetoresistance with disorder level.

Abstract

Robustness to disorder - the defining property of any topological state - has been mostly tested in low-disorder translationally-invariant materials systems where the protecting underlying symmetry, such as time reversal, is preserved. The ultimate disorder limits to topological protection are still unknown, however, a number of theories predict that even in the amorphous state a quantized conductance might yet reemerge. Here we report a directly detected robust spin response in structurally disordered thin films of the topological material Sb2Te3 free of extrinsic magnetic dopants, which we controllably tune from a strong (amorphous) to a weak crystalline) disorder state. The magnetic signal onsets at a surprisingly high temperature (~ 200 K) and eventually ceases within the crystalline state. We demonstrate that in a strongly disordered state disorder-induced spin correlations dominate the transport of charge - they engender a spin memory phenomenon, generated by the nonequilibrium charge currents controlled by localized spins. The negative magnetoresistance (MR) in the extensive spin-memory phase space is isotropic. Within the crystalline state, it transitions into a positive MR corresponding to the weak antilocalization (WAL) quantum interference effect, with a 2D scaling characteristic of the topological state. Our findings demonstrate that these nonequilibrium currents set a disorder threshold to the topological state; they lay out a path to tunable spin-dependent charge transport and point to new possibilities of spin control by disorder engineering of topological materials