Regensburg 2016 – scientific programme
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DS: Fachverband Dünne Schichten
DS 51: Transport: Spintronics and Magnetotransport
(Joint session of DS, HL, MA and TT, organized by TT)
DS 51.2: Talk
Thursday, March 10, 2016, 16:45–17:00, H23
Shot noise in magnetic tunnel junctions: effect of the geometric phase — •Tim Ludwig1 and Alexander Shnirman1,2 — 1Institut für Theorie der Kondensierten Materie, Karlsruher Institut für Technologie, 76131 Karlsruhe, Germany — 2L. D. Landau Institute for Theoretical Physics RAS, Kosygina street 2, 119334 Moscow, Russia
We analyze the current driven dynamics of magnetization and voltage in a magnetic tunnel junction.
As predicted in [1, 2], the magnetization can be driven by spin currents. This effect can also be reversed, such that an externally driven magnetization generates a dc voltage [3]. Although both effects are intimately related, so far they have been treated separately. We generalize the approach of [4] to derive an action that contains both effects simultaneously.
We employ the Keldysh formalism, which allows us to derive stochastic Landau-Lifshitz-Gilbert-Langevin equations describing the angular dynamics of the magnetization coupled with the voltage dynamics. We identify two low-temperature regimes. In one regime the voltage fluctuations are governed by the applied current only, as expected for the shot noise. In the other regime an excess noise arises, which is
governed by the geometric phase of the precessing magnetization.
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