XXXVI Reunión Bienal de la Real Sociedad Española de Física

Topological transitions in spin dynamics by geometric phase engineering

Not scheduled

Aula Magna (Santiago de Compostela, Facultade de Química)

Quantum Materials and Technologies (GEFES)

Description

Research on spin geometric (Berry) phases in mesoscopic systems has been active for about 25 years already. Still, incontrovertible evidence of spin geometric phases was found only recently [1] in mesoscopic rings subject to spin-orbit coupling (Rashba rings) in agreement with theoretical predictions [2], giving a new impulse to the field. Here, we discuss some new possibilities for electronic manipulation based on the control of the spin geometric phases in nanodevices such as Rashba interferometers subject to additional magnetic fields. These run from a purely geometric manipulation of electron spins (for weak fields) [3] to topological transitions (for large fields) [4]. Moreover, we notice that similar physics plays a role in spin resonance under driving fields that undergo a topological transition. There we find [5] that, despite the strongly non-adiabatic effects dominating the spin dynamics, the field's topology appears clearly imprinted in the quasienergy of Floquet spin states. This has remarkable consequences on the spin resonance condition, suggesting a whole new class of experiments to spot topological transitions in the dynamics of spins and other two-level systems (from nuclear magnetic resonance to strongly-driven superconducting quits). [1] F. Nagasawa, J. Takagi, Y. Kunihashi, M. Kohda, and J. Nitta, Phys. Rev. Lett. 108, 086801 (2012); K. Richter, Physics 5, 22 (2012). [2] D. Frustaglia and K. Richter, Phys. Rev. B 69, 235310 (2004). [3] F. Nagasawa, D. Frustaglia, H. Saarikoski, K. Richter, and J. Nitta, Nature Comm. 4, 2526 (2013). [4] H. Saarikoski, J.E. Vázquez-Lozano, J.P. Baltanás, F. Nagasawa, J. Nitta, and D. Frustaglia, Phys. Rev. B 91, 241406(R) (2015). [5] A.A. Reynoso, J.P. Baltanás, H. Saarikoski, J.E. Vázquez-Lozano, J. Nitta, and D. Frustaglia, arXiv:1702.0178, to appear in New J. Phys. (2017).