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Localizing quantum phase slips in one-dimensional Josephson junction chains
KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.ORCID iD: 0000-0003-0493-7792
KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.ORCID iD: 0000-0002-9881-7857
KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
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2013 (English)In: New Journal of Physics, ISSN 1367-2630, Vol. 15, 095014- p.Article in journal (Refereed) Published
Abstract [en]

We studied quantum phase-slip (QPS) phenomena in long one-dimensional Josephson junction series arrays with tunable Josephson coupling. These chains were fabricated with as many as 2888 junctions, where one sample had a separately tunable link in the middle of the chain. Measurements were made of the zero-bias resistance, R-0, as well as current-voltage characteristics (IVC). The finite R-0 is explained by QPS and shows an exponential dependence on root E-J/E-C with a distinct change in the exponent at R-0 = R-Q = h/4e(2). When R-0 > R-Q, the IVC clearly shows a remnant of the Coulomb blockade, which evolves to a zero-current state with a sharp critical voltage as E-J is tuned to a smaller value. The zero-current state below the critical voltage is due to coherent QPSs and we show that these are enhanced when the central link is weaker than all other links. Above the critical voltage, a negative, differential resistance is observed, which nearly restores the zero-current state.

Place, publisher, year, edition, pages
2013. Vol. 15, 095014- p.
Keyword [en]
Small Tunnel-Junctions, Charge Solitons, Arrays, Superconductivity, Transition, Nanowires, Vortices
National Category
Physical Sciences
URN: urn:nbn:se:kth:diva-131716DOI: 10.1088/1367-2630/15/9/095014ISI: 000324795400004ScopusID: 2-s2.0-84885158666OAI: diva2:657121
Swedish Research Council

QC 20131018

Available from: 2013-10-18 Created: 2013-10-17 Last updated: 2013-11-04Bibliographically approved
In thesis
1. Nonlinear dynamics of Josephson Junction Chains and Superconducting Resonators
Open this publication in new window or tab >>Nonlinear dynamics of Josephson Junction Chains and Superconducting Resonators
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents the results of the experimental studies on two kindof Superconducting circuits: one-dimensional Josephson junction chains andsuperconducting coplanar waveguide (CPW) resonators. One-dimensionalJosephson junction chains are constructed by connecting many Superconducting quantum interference devices (SQUIDs) in series. We have studied DC transport properties of the SQUID chains and model their nonlineardynamics with Thermally Activated Phase-Slips (TAPS). Experimental andsimulated results showed qualitative agreement revealing the existence of auniform phase-slipping and phase-sticking process which results in a voltage-independent current on the dissipative branch of the current-voltage char-acteristics (IVC). By modulating the effective Josephson coupling energy ofthe SQUIDs (EJ ) with an external magnetic field, we found that the ratio EJ /EC is a decisive factor in determining the qualitative shape of theIVC. A quantum phase transition between incoherent Quantum Phase Slip, QPS (supercurrent branch with a finite slope) to coherent QPS (IVC withwell-developed Coulomb blockade) via an intermediate state (supercurrentbranch with a remnant of Coulomb blockade) is observed as the EJ /EC ratio is tuned. This transition from incoherent QPS to the intermediate-statehappens around R0 ∼ RQ (RQ = h/4e^2 = 6.45kΩ). We also fabricated structured chains where a SQUID at the middle of the chain (central SQUID) has different junction size and loop area compared to other SQUIDs in the chain. Results showed that with these structured chains it is possible to localize andtune the amplitude of both TAPS and QPS at the central SQUID.

The second part of the thesis describes the fabrication process and themeasurement results of superconducting CPW resonators. Resonators withdifferent design parameters were fabricated and measured. The transmissionspectra showed quality factors up to, Q ∼ 5 × 10^5 . We have observed bendingof the resonance curves to the lower frequencies due to existence of a nonlinear kinetic inductance. The origin of the nonlinear kinetic inductance isthe nonlinear relation between supercurrent density, Js, and superfluid veloc-ity, vs , of the charge carriers on the center line of the resonators. A simplemodel based on the Ginzburg-Landau theory is used in order to explain ob-served nonlinear kinetic inductance and estimates using this model showedgood agreement with the experimental results.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. vi, 119 p.
Trita-FYS, ISSN 0280-316X ; 13:52
Superconductivity, Josephson Junction, SQUID, Superconducting Resonators
National Category
Condensed Matter Physics
urn:nbn:se:kth:diva-132238 (URN)978-91-7501-869-0 (ISBN)
Public defence
2013-11-28, FA32, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (English)
EU, FP7, Seventh Framework Programme

QC 20131030

Available from: 2013-11-04 Created: 2013-10-24 Last updated: 2013-11-04Bibliographically approved

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