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Title: Macroscopic quantum tunneling in small Josephson junctions in a magnetic field.

Abstract

We study the phenomenon of macroscopic quantum tunneling (MQT) in small Josephson junctions (JJ) with an externally applied magnetic field. The latter results in the appearance of the Fraunhofer type modulation of the current density along the barrier. The problem of MQT for a pointlike JJ is reduced to the motion of the quantum particle in the washboard potential. In the case of a finite size JJ under consideration, this problem corresponds to a MQT in a potential which itself, besides the phase, depends on space variables. The general expression for the crossover temperature To between thermally activated and macroscopic quantum tunneling regimes and the escaping time {tau}{sub esc} have been calculated.

Authors:
; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC); MIUR; Russian Foundation Basic Research
OSTI Identifier:
919350
Report Number(s):
ANL/MSD/JA-60417
Journal ID: ISSN 0031-9007; PRLTAO; TRN: US0806355
DOE Contract Number:
DE-AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Phys. Rev. Lett.; Journal Volume: 99; Journal Issue: 2007
Country of Publication:
United States
Language:
ENGLISH
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CURRENT DENSITY; JOSEPHSON JUNCTIONS; MAGNETIC FIELDS; MODULATION; TUNNELING

Citation Formats

Ovchinnikov, Yu. N., Barone, A., Varlamov, A. A., Materials Science Division, Max-Planck Inst. for Physics of Complex Systems, Landau Inst. Theoretical Physics, Univ. di Napoli Federico II, and Coherentia-INFM, CNR. Macroscopic quantum tunneling in small Josephson junctions in a magnetic field.. United States: N. p., 2007. Web. doi:10.1103/PhysRevLett.99.037004.
Ovchinnikov, Yu. N., Barone, A., Varlamov, A. A., Materials Science Division, Max-Planck Inst. for Physics of Complex Systems, Landau Inst. Theoretical Physics, Univ. di Napoli Federico II, & Coherentia-INFM, CNR. Macroscopic quantum tunneling in small Josephson junctions in a magnetic field.. United States. doi:10.1103/PhysRevLett.99.037004.
Ovchinnikov, Yu. N., Barone, A., Varlamov, A. A., Materials Science Division, Max-Planck Inst. for Physics of Complex Systems, Landau Inst. Theoretical Physics, Univ. di Napoli Federico II, and Coherentia-INFM, CNR. Mon . "Macroscopic quantum tunneling in small Josephson junctions in a magnetic field.". United States. doi:10.1103/PhysRevLett.99.037004.
@article{osti_919350,
title = {Macroscopic quantum tunneling in small Josephson junctions in a magnetic field.},
author = {Ovchinnikov, Yu. N. and Barone, A. and Varlamov, A. A. and Materials Science Division and Max-Planck Inst. for Physics of Complex Systems and Landau Inst. Theoretical Physics and Univ. di Napoli Federico II and Coherentia-INFM, CNR},
abstractNote = {We study the phenomenon of macroscopic quantum tunneling (MQT) in small Josephson junctions (JJ) with an externally applied magnetic field. The latter results in the appearance of the Fraunhofer type modulation of the current density along the barrier. The problem of MQT for a pointlike JJ is reduced to the motion of the quantum particle in the washboard potential. In the case of a finite size JJ under consideration, this problem corresponds to a MQT in a potential which itself, besides the phase, depends on space variables. The general expression for the crossover temperature To between thermally activated and macroscopic quantum tunneling regimes and the escaping time {tau}{sub esc} have been calculated.},
doi = {10.1103/PhysRevLett.99.037004},
journal = {Phys. Rev. Lett.},
number = 2007,
volume = 99,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • We study the effect of the phase dependence of the effective capacitance of Josephson junctions on macroscopic quantum tunneling. We calculate the correction due to the nonlinearity of the capacitance on the rate of escape out of a metastable well, in the presence of Ohmic dissipation, and discuss its dependence on the parameters of the junction. We show that the correction tends to enhance the escape rate and that the enhancement becomes more pronounced as the self-capacitance or the normal-state resistance of the junction is reduced.
  • The effect of dissipation on macroscopic quantum tunneling in Josephson junctions is investigated. It is shown that friction can lead to an increase in the lifetime of the metastable state of the junction. It is found that a sharp division of the tunneling probability into a purely quantum-mechanical probability for tunneling in the absence of friction and a probability for dissipation-involving tunneling is possible only in the case of weak friction.
  • Macroscopic quantum tunneling (MQT) in a Josephson junction (JJ) is considered. The typical I-V curve of a JJ is used for the expressions of the tunneling and thermal activation rates of the phase of a JJ in order to help clarify the role of the dynamical resistance in MQT in Josephson junctions. The participating parameters in the expressions of the rates are experimentally independently measurable.
  • Many theoretical studies and some experiments have shown the possibility of several new secondary quantum effects in small Josephson junctions at low temperatures. We show that, within the well-established quantum picture of the junction, it is possible to experimentally observe sharp voltage peaks at certain current values. Such peaks are related to a resonant macroscopic quantum tunneling between levels in neighboring wells of the proper washboard potential having close energies. The proposed experiment, with respect to experiments on Coulomb blockade or Block oscillations, requires a larger junction area, reducing the technological difficulties in making the samples. 7 refs., 2 figs.
  • Macroscopic quantum tunneling in a long-overlap Josephson junction (JJ) is considered. Expressions for the nucleation rate of the phase of the JJ in the tunneling and thermal-activation regimes are presented.