Observation of a gradual collective excitation of a geometrical resonance in an array of Nb/NbSi/Nb Josephson junctions with increasing number of synchronized junctions
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2023-07-15 14:37
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KRASNOV, Vladimir. Observation of a gradual collective excitation of a geometrical resonance in an array of Nb/NbSi/Nb Josephson junctions with increasing number of synchronized junctions. In: The 12th international conference on intrinsic Josephson effect and horizons of superconducting spintronics, 22-25 octombrie 2021, Chişinău. Chişinău: 2021, p. 48. ISBN 978-9975-47-215-9.
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The 12th international conference on intrinsic Josephson effect and horizons of superconducting spintronics 2021
Conferința "The 12th international conference on intrinsic Josephson effect and horizons of superconducting spintronics"
Chişinău, Moldova, 22-25 octombrie 2021

Observation of a gradual collective excitation of a geometrical resonance in an array of Nb/NbSi/Nb Josephson junctions with increasing number of synchronized junctions


Pag. 48-48

Krasnov Vladimir12
 
1 Stockholm University,
2 Moscow Institute of Physics and Technology
 
Disponibil în IBN: 18 martie 2022


Rezumat

Synchronization of many Josephson junctions (JJs) is required for achieving significant emission power from Josephson oscillators [1]. One of the most promising strategies of synchronization is via collective excitation of a geometrical resonance either inside [1] or outside [2] the junction. Successful synchronization of up to 9000 JJ’s coupled to an external cavity mode, accompanied by a coherent superradiant emission, has been demonstrated in a 1D junction array [3]. However, dynamics of such synchronization is not fully understood: it depends strongly on the array geometry [3], a specific mode of the geometrical resonance [2,3] and many other factors [1]. Here we study experimentally a 1D array of Nb/NbSi/Nb JJ’s, consisting of 7 meander lines with 1000 JJs in each line, similar to those studied in Refs. [2,3]. The JJs exhibit a hysteresis in current- voltage (I-V) characteristics, presumably of thermal origin. Presence of a small inhomogeneity (specifically introduced by applying a small magnetic field) together with the hysteresis, allows one-by-one switching of JJs from the superconducting to the resistive state. We observe that above a certain number of JJs, N≳100, a resonant step starts to develop in the I-V. As shown in Ref. [3] the step is caused by a collective excitation of a cavity mode in the array electrode. The step amplitude gradually increases with increasing N, which is accompanied by a parabolic-like enhancement of the emission power, measured with an external bolometer. Our observation provides a clear evidence for the mutual feedback between the cavity mode and the oscillating JJs. Such the feedback provides an effective mechanism for array synchronization and coherent emission.