Strong spin-dephasing in a topological insulator - paramagnet heterostructure

TL;DR

This study demonstrates that interfacing a topological insulator with a kagome-lattice paramagnet causes strong spin dephasing, suppressing spin-momentum locking and affecting transport properties, with implications for topological device engineering.

Contribution

It reveals how magnetic heterostructures can induce strong spin dephasing in topological insulators, advancing understanding of spin transport manipulation at interfaces.

Findings

Suppression of weak antilocalization in heterostructures at monolayer thickness

Unordered Co moments cause stronger dephasing than non-magnetic Co$^{3+}$

Magnetic interfaces significantly alter spin-polarized transport in topological insulators

Abstract

The interface between magnetic materials and topological insulators can drive the formation of exotic phases of matter and enable functionality through manipulation of the strong spin polarized transport. Here, we report that the spin-momentum-locked transport in the topological insulator Bi$_2$Se$_3$ is completely suppressed by scattering at a heterointerface with the kagome-lattice paramagnet, Co$_7$Se$_8$. Bi$_2$Se$_{3-}$Co$_7$Se$_{8-}$Bi$_2$Se$_3$ trilayer heterostructures were grown using molecular beam epitaxy. Magnetotransport measurements revealed a substantial suppression of the weak antilocalization effect for Co$_7$Se$_8$ at thicknesses as thin as a monolayer, indicating a strong dephasing mechanism. Bi$_{2-x}$Co$_x$Se$_3$ films, where Co is in a non-magnetic $3^+$ state, show weak antilocalization that survives to $x = 0.5$, which, in comparison with the heterostructures, suggests the unordered moments of the Co$^{2+}$ act as a far stronger dephasing element. This work highlights several important points regarding spin-polarized transport in topological insulator interfaces and how magnetic materials can be integrated with topological materials to realize both exotic phases as well as novel device functionality.