K. Yu. Arutyunov,University of Jyväskylä, Finland

Jeudi 24 Janvier 2013, 14h
Amphi Howleck, Esc C, 1ème etage

Quantum fluctuations in superconducting nanostructures : physics and applications

K. Yu. Arutyunov
University of Jyväskylä, Department of Physics, NanoScience Centre, PB 35, 40014 Jyväskylä, Finland and Nuclear Physics Institute, Moscow State University, 119992 Moscow, Russiace

The topic of quantum fluctuations in quasi-1D superconductors, also called quantum phase slips (QPS), has attracted a significant attention [1]. It has been shown that the phenomenon is capable to suppress the zero resistivity of ultra-narrow superconducting nanowires at low temperatures T<<Tc [2-4] and quench persistent currents in tiny nanorings [5]. It has been predicted that a superconducting nanowire in the regime of QPS is dual to a Josephson junction [6]. In particular case of an extremely narrow superconducting nanowire imbedded in a high-impedance environment the duality leads to an intuitively controversial result : the superconductor should enter an insulating state. Here we experimentally demonstrate [7] that the I-V characteristic of such a wire indeed shows Coulomb blockade which disappears with application of a critical magnetic field and/or above the critical temperature proving that the effect is related to superconductivity. The quantum duality with Josephson systems goes even further : application of an external RF radiation can be synchronized with the internal Bloch oscillations of the current-biased ‘superconducting’ nanowire. The phenomenon is dual to the well-known Shapiro effect : the voltage steps for a Josephson junction are substituted by the current steps for a QPS wire. The position of the n-th step follows the relation In=n×(2e)×f, where f is the frequency of external RF radiation and 2e is the charge of a Cooper pair. In addition to a significant importance for basic science, utilization of the QPS effect is expected to lead to the important metrological application - the quantum standard of electric current [7] and the new generation of quantum logic devices – qubits [8].

[1] K. Yu. Arutyunov, D. S. Golubev, and A.D. Zaikin, Phys. Rep. 464, 1 (2008).
[2] M. Zgirski, K.-P. Riikonen, V. Touboltsev, and K. Arutyunov, NanoLett. 5, 1029 (2005).
[3] M. Zgirski, K.-P. Riikonen, V. Touboltsev and K.Yu. Arutyunov, Phys. Rev. B 77, 054508 (2008).
[4] J. S. Lehtinen, T. Sajavaara, K. Yu. Arutyunov, M. Yu. Presnjakov and A. Vasiliev, Phys. Rev. B 85, 094508 (2012).
[5] K. Yu. Arutyunov, T. T. Hongisto, J. S. Lehtinen, L. I. Leino, and A. L. Vasiliev. Nature : Sci. Rep. 2, 293 (2012).
[6] J. E. Mooij and Yu. V. Nazarov, Nature Physics 2, 169 (2006).
[7] J. S. Lehtinen, K. Zakharov and K. Yu. Arutyunov, Phys. Rev. Lett. 109, 187001 (2012)
[8] O. V. Astafiev, L. B. Ioffe, S. Kafanov, Yu. A. Pashkin, K. Yu. Arutyunov, D. Shahar, O. Cohen, & J. S. Tsai, Nature 484, 355 (2012).

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