Fluctuations and Correlations in Semiconductor Spintronics
Final Report Abstract
Recent progress in controlling spin and charge degrees of freedom in semiconductor nano-devices allowed performing experimental studies of non-equilibrium statistical physics in quantum systems, and more progress is to be expected. Vice versa, the recent progress in theoretical statistical physics out of equilibrium and in the quantum regime should provide an approach to better understand fluctuation effects in mesoscopic and spintronic devices. The aim of our project was to understand correlations of fluctuations in semiconductor spintronics from the view of the non-equilibrium statistical physics. The expected knowledge gain obtained in this project can be used to improve the performance of the spintronics devices. The plans of the joint project were the following; (a) verification of the fluctuation theorem in real time for direction-resolved single-electron tunneling in quantum dot systems, and (b) the study of spin and electron correlations in spintronics devices. (a): We were successful in verifying the fluctuation theorem (FT) beyond our original expectation. During the project we could start collaborations with three experimental groups and produced several publications with them. (1) We interpreted the results of the group NTT Basic Research Laboratories on bi-directional electron counting in double quantum-dot, measured by a quantum point contact electrometer. (2) Similar but quantitatively more precise measurements were performed later in the group of Prof. Klaus Ensslin at ETH Zurich. (3) The quantum FT was verified experimentally in an Aharonov-Bohm interferometer by the Group of Prof. Kensuke Kobayashi in Kyoto University (now at Osaka University). In particular, we studied the time resolution and the back-action effects of the measurement devices. To do this, we fully utilized the Keldysh real-time diagrammatic expansion of the reduced density matrix. In addition, we used the theory of the full counting statistics in discrete Markov master equations. (b): With a view on quantum information devices based on the nuclear spins in semiconductor quantum dots we performed numerical simulations of spin correlations and spin dynamics.
Publications
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Bidirectional Single-Electron Counting and the Fluctuation Theorem, Physical Review B, Vol. 81.2010, Iss. 12, 125331.
Y. Utsumi, D.S. Golubev, M. Marthaler, K. Saito, T. Fujisawa, G. Schön
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Single-Electron Counting and the Fluctuation Theorem, in: Perspectives of Mesoscopic Physics - dedicated to Joseph Imry's 70th Birthday, Eds. A. Aharony and O. Entin-Wohlman, pp. 397-414, World Scientific (2010), ISBN 978-981-4299-43-5.
Y. Utsumi, D. S. Golubev, M. Marthaler, T. Fujisawa, and G. Schön
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Fluctuation theorem for a double quantum dot coupled to a point-contact electrometer, Physical Review B, Vol. 84.2011, Iss. 7, 075323.
D. S. Golubev, M. Marthaler, Y. Utsumi, G. Schön
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Irreversibility on the Level of Single-Electron Tunneling, Physical Review X, Vol. 2.2012, Iss. 1, 011001.
B. Küng, C. Rössler, M. Beck, M. Marthaler, D.S. Golubev, Y. Utsumi, T. Ihn, K. Ensslin
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Numerical Study on Spin Torque Switching in Thermally Activated Region. Applied Physics Express, Vol. 5. 2012, Number 6, 063009.
T. Taniguchi, M. Shibata, M. Marthaler, Y. Utsumi, and H. Imamura
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Work fluctuation theorem for a classical circuit coupled to a quantum conductor, Phys. Rev. B, Vol. 86. 2012, Iss. 7, 075420.
Y. Utsumi, D. S. Golubev, M. Marthaler, G. Schön, and K. Kobayashi
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Spin torque switching of an in-plane magnetized system in a thermally activated region. Physical Reviews B, Vol. 87. 2013, Issue 5, 054406.
T. Taniguchi, Y. Utsumi, M. Marthaler, D. S. Golubev, and H. Imamura
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Test of the fluctuation theorem for single-electron transport, Journal of Applied Physics, Vol. 113. 2013, Issue 13, 136507.
B. Küng, C. Rössler, M. Beck, M. Marthaler, D. S. Golubev, Y. Utsumi, T. Ihn, and K. Ensslin
