Tunneling Planar Hall Effect in Topological Insulators: Spin-Valves and Amplifiers

TL;DR

This paper explores how tunneling across ferromagnetic barriers on topological insulators induces a giant planar Hall effect, enabling control of conductance and potential applications in spin-valves and amplifiers.

Contribution

It demonstrates electrostatic control of tunneling Hall conductance and sign reversal of conductance without opening a gap in topological surface states.

Findings

Giant tunneling planar Hall conductance exceeding longitudinal conductance.

Sign reversal of conductance by changing magnetization direction.

Transport can be switched from spin-valve to amplifier mode.

Abstract

We investigate tunneling across a single ferromagnetic barrier on the surface of a three-dimensional topological insulator. In the presence of a magnetization component along the bias direction, a tunneling planar Hall conductance (TPHC), transverse to the applied bias, develops. Electrostatic control of the barrier enables a giant Hall angle, with the TPHC exceeding the longitudinal tunneling conductance. By changing the in-plane magnetization direction it is possible to change the sign of both the longitudinal and transverse differential conductance without opening a gap in the topological surface state. The transport in a topological insulator/ferromagnet junction can thus be drastically altered from a simple spin-valve to an amplifier.