Mesoscopic electron focusing in topological insulators

TL;DR

This paper demonstrates mesoscopic focusing of coherent charge density oscillations in topological insulators through magnetic surface doping, revealing long-distance spin information transmission and broad applicability to systems with spin-orbit interactions.

Contribution

It introduces a method to achieve mesoscopic electron focusing in topological insulators, enabling long-range spin information transfer via coherent quantum effects.

Findings

Mesoscopic focusing observed at large energy contour segments.

Magnetic surface doping enables anisotropic Dirac fermion interactions.

Results applicable to systems with spin-orbit lifted degeneracy.

Abstract

The particle wave duality sets a fundamental correspondence between optics and quantum mechanics. Within this framework, the propagation of quasiparticles can give rise to superposition phenomena which, like for electromagnetic waves, can be described by the Huygens principle. However, the utilization of this principle by means of propagation and manipulation of quantum information is limited by the required coherence in time and space. Here we show that in topological insulators, which in their pristine form are characterized by opposite propagation directions for the two quasiparticles spin channels, mesoscopic focusing of coherent charge density oscillations can be obtained at large nested segments of constant energy contours by magnetic surface doping. Our findings provide evidence of strongly anisotropic Dirac fermion-mediated interactions. Even more remarkably, the validity of our findings goes beyond topological insulators but applies for systems with spin orbit lifted degeneracy in general. It demonstrates how spin information can be transmitted over long distances, allowing the design of experiments and devices based on coherent quantum effects in this fascinating class of materials.