Nanoscale physics

RF-dynamics of vortex kinks in the mixed state of nanostructured superconductors with columnar defects
Boliasova O.O.1, Kasatkin A.L.2, Pokusinskii A.O.3, Shapovalov A.P.4, Tsvitkovskyi V.P.2
1 Donetsk Institute for Physics and Engineering Named after O. O. Galkin, NAS of Ukraine, Nauky Ave., 46, Kyiv-03028, Ukraine.
E-mail: ol.boliasova@gmail.com 
2 G. V. Kurdyumov Institute for Metal Physics, NAS of Ukraine, 36 Academician Vernadsky Blvd., Kyiv-03142, Ukraine.
3 Taras Shevchenko National University of Kyiv, Volodymyrska St, 60, Kyiv-01033, Ukraine.
4 Kyiv Academic University, 36 Academician Vernadsky Blvd., Kyiv-03142, Ukraine.

We suggest a theoretical model for the microwave response of Abrikosov vortices in nanostructured superconductors with columnar defects which serve as effective pinning sites for vortices that are considered as the elastic strings [1]. For this case, we suppose that microwave losses related to the vortex oscillations in a microwave field arise caused by viscous oscillations of vortex kinks, which connect different parts of the vortex line pinned on adjacent columnar defects. In what follows it is supposed that there is rigid pinning of vortex parts settled on columnar defects while vortex kinks can viscously move along the columnar defect axis under the Lorentz force action. At high enough temperatures vortex kinks arise as thermal excitations of the whole vortex lines settled in potential wells produced by columnar defects. In this case, the kinks attract to the flat specimen surface and their concentration inside the superconductor should obey the barometric law. For the case of inclined magnetic field H, rf losses due to viscous kinks oscillations under the microwave current action arise even at T=0 if the inclination angle H concerning the columnar pinning site axis (z-axis) exceeds some locking angle value L [2].

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2.	Blatter G., Feigel’man M.V., Geshkenbein V.B., Larkin A.I., and Vinokur V.M. Vortices in high-temperature superconductors // Rev. Mod. Phys.-1994.-66, N 4.-P. 1125-1388.