Scaling Behavior of Quasi-One-Dimensional Vortex Avalanches in Superconducting Films

A J Qviller,T H Johansen,P Mikheenko,J B Hansen,T Qureishy,J I Vestgården,Y Xu,H Suo,P B Mozhaev

doi:10.1038/s41598-020-62601-y

A J Qviller, T H Johansen + Show 7 more

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https://doi.org/10.1038/s41598-020-62601-y

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Scaling behaviour of dynamically driven vortex avalanches in superconducting YBa2Cu3O7−δ films deposited on tilted crystalline substrates has been observed using quantitative magneto-optical imaging. Two films with different tilt angles are characterized by the probability distributions of avalanche size in terms of the number of moving vortices. It is found in both samples that these distributions follow power-laws over up to three decades, and have exponents ranging between 1.0 and 1.4. The distributions also show clear finite-size scaling, when the system size is defined by the depth of the flux penetration front – a signature of self-organized criticality. A scaling relation between the avalanche size exponent and the fractal dimension, previously derived theoretically from conservation of the number of magnetic vortices in the stationary state and shown in numerical simulations, is here shown to be satisfied also experimentally.

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Avalanche behaviour is found in a wide range of natural systems, and is commonly observed, e.g., as abrupt displacement in granular media, earthquakes, Barkhausen noise caused by sudden motion of magnetic domain walls in ferromagnetic materials, and abrupt displacement of vortices in superconductors, where their dissipative motion can trigger thermomagnetic avalanches[1,2,3,4]
The obtained avalanche size exponents are in the same range as those found in the present work, but the obtained fractal dimensions differ considerably
The probability distributions of flux avalanches were measured by quantitative magneto-optical imaging (MOI) for two YBCO samples deposited on substrates cut with tilt angles of 14° and 20°

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Avalanche behaviour is found in a wide range of natural systems, and is commonly observed, e.g., as abrupt displacement in granular media, earthquakes, Barkhausen noise caused by sudden motion of magnetic domain walls in ferromagnetic materials, and abrupt displacement of vortices in superconductors, where their dissipative motion can trigger thermomagnetic avalanches[1,2,3,4]. SOC seems to capture basic aspects of sandpile physics, both particle rolling and inertial effects tend to create system-spanning avalanches, which introduce cutoffs in the power-law probability distributions already after approximately one decade[1]. Such cutoffs are seen in results obtained by numerical simulations[6]. For thin films in perpendicular magnetic fields, the analogy is less obvious,[12,13] since there the flux density gradient is not constant, the critical state is still characterized by jc

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