Nitin Samarth

Affiliations

Department of Physics, Penn State University, University Park PA 16802, USA

Title

Topological spintronics

Abstract

We provide a perspective on the emergence of "topological spintronics," which exploits the helical spin texture of two-dimensional surface states in three-dimensional topological insulators. Spin- and angle-resolved photoemission spectroscopy shows how this spin texture can be engineered using quantum tunneling between surfaces [1] while spin transport devices allow all electrical measurements of the underlying spin-momentum locking [2,3]. In bilayers of a topological insulator and a ferromagnetic metal, we find evidence for a highly efficient charge-to-spin conversion at room temperature, measured through both spin torque ferromagnetic resonance [4] and through spin pumping [5]. When time-reversal symmetry is broken in a ferromagnetic topological insulator, a quantum anomalous Hall insulator emerges at cryogenic temperatures, characterized by a precisely quantized Hall resistance and vanishing longitudinal resistance [6]. The "giant" anisotropic magnetoresistance of quantum anomalous Hall insulators provides quantitative insights into the interplay between dissipation-free edge state transport and co-existing dissipative channels in regimes away from perfect quantization [7]. Various aspects of this work were supported by DARPA, ONR, ARO MURI and by C-SPIN, one of six centers of STARnet, a Semiconductor Research Corporation program, sponsored by MARCO and DARPA.

References

• [1] M. Neupane, A. Richardella et al., Nature Communications 5, 3841 (2014).
• [2] Luqiao Liu et al., Phys. Rev. B 91, 235437 (2015).
• [3] J. S. Lee et al., arxiv:1507.07063.
• [4] A. Mellnik, J. S. Lee, A. Richardella et al., Nature 511, 449 (2014).
• [5] M. Jamali et al., arxiv:1407.7940
• [7] A. Kandala, A. Richardella, et al., Nature Communications 6, 7434 (2015).