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# CM-AMO SEMINAR

New Twists in Spintronics: Exploiting the Echoes of Special Relativity in Condensed Matter Physics

Understanding the origin and properties of different phases of complex materials and how to control them is at the heart of condensed matter physics. One of the grand challenges of the field is controlling spin and magnetic dependent properties by only electrical means. To do so, one must resort to the spin-orbit coupling (SOC), which is one of the few echoes of special relativity in condensed-matter physics that couples the spin and charge of the electron. While the weak SOC regime is relatively well understood, the SOC regime remains one of the most theoretically challenging at a fundamental level. Research in this regime has given rise to new physical insights in established phenomena, such as the anomalous Hall effect (AHE), new directions in recent fields such as magnetic spin-transfer torque dynamics, and new emerging frontiers, such as topological insulators and spin-caloritronics. I will broadly describe how we have exploited SOC to create new paradigms of enhanced control of spin properties and discovered unexpected links between seemingly disparate ideas as topology, materials science, ferromagnetism, and thermoelectricity. This will take us from recent insights on the AHE which lead to the spin-Hall effect and topological insulators (1,2), to the realization of a spin-transistor based on spin-helix state (3,4) and to a way of increasing thermoelectric efficiency by exploiting the topological properties of the band structure imparted by the strong SOC in topological insulators (5). These are joint theoretical and experimental efforts, with each taking alternate leading roles in a unique fast paced spintronics tango (6).

References:

- N. Nagaosa, Jairo Sinova, S. Onoda, A.H. MacDonald, and P. Ong, “Anomalous Hall Effect,” Rev. of Mod. Phys. 82, 1539 (2010).
- Alexey Kovalev, Jairo Sinova, Y. Tserkovnyak, “Anomalous Hall Effect in Disordered Multi-band Metals,” Phys. Rev. Let.. 105, 036601 (2010); Juergen Weischenberg, Frank Freimuth, Jairo Sinova, Stefan Blugel, and Yuriy Mokrousov, “Ab Initio Theory of Scattering-Independent Anomalous Hall Effect,” Phys. Rev. Lett. 107, 106601 (2011); Xiong-Jun Liu, Xin Liu, and Jairo Sinova, “Scaling of the anomalous Hall effect in the insulating regime,” Phys. Rev. B 84, 165304 (2011).
- J. Wunderlich, B.G. Park, A.C. Irvine, L.P. Zarbo, E. Rozkotova, P.Nemec, V. Novak, Jairo Sinova, T. Jungwirth, “Sping Hall effect transistor,” Science 330, 1801 (2010).
- J. Wunderlich, A.C. Irvine, Jairo Sinova, B.G. Park, X.L. Xu, B. Kaestner, V. Novak, and T. Jungwirth, “Spin-injection Hall effect in a planar photovoltaic cell,” Nature Physics 5, 675 (2009).
- O. A. Tretiakov, Ar. Abanov, S. Murakami, and Jairo Sinova, “Large thermoelectric figure of merit for 3D topological Anderson insulators via line dislocation engineering,” Appl. Phys. Letts. 97, 073108 (2010); Oleg A. Tretiakov, Ar. Abanov, Jairo Sinova, “Holey topological thermoelectrics,” Appl. Phys. Lett. 99, 113110 (2011).
- Jairo Sinova and Igor Zutic, “New moves of the spintronics tango,” Nature 11, 368 (2012).