“Topological Spintronics” by Nitin Samarth (Penn State University)

Wednesday, March 2, 2016 - 4:00pm
Condensed Matter Physics Journal club Seminar

We provide a perspective on the recent 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 for 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 [4]. 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, despite the presence of significant magnetic inhomogeneity [5]. The “giant“ anisotropic magneto-resistance of the quantum anomalous Hall insulator provides quantitative insights into the interplay between dissipation-free edge state transport and co-existing dissipative channels in regimes away from perfect quantization [6]. 

[1] M. Neupane, A. Richardella et al., Nature Communications 5, 3841 (2014).

[2] Luqiao Liu, A. Richardella et al., Phys. Rev. B 91, 235437 (2015).

[3] J. S. Lee, A. Richardella et al., Phys. Rev. B 92, 155312 (2015) .

[4] A. Mellnik, J. S. Lee, A. Richardella et al., Nature 511, 449 (2014).

[5] E. Lachman et al., Science Advances 1, e1500740 (2016).

[6] A. Kandala, A. Richardella, et al., Nature Communications 6, 7434 (2015).

PAB 4-330