Slowing down of vortex motion at the Berezinskii-Kosterlitz-Thouless transition in ultrathin NbN films

Abstract

We present a quantitative comparison between the measurements of the complex conductance at low (kHz) and high (GHz) frequency in a thin superconducting film of NbN and the theoretical predictions of the dynamical Beresinksii-Kosterlitz-Thouless theory. While the data in the GHz regime can be well reproduced by extending the standard approach to the realistic case of a inhomogeneous sample, the low-frequency measurements present an anomalously large dissipative response around Tc. This anomaly can only be accounted for by assuming a strong slowing down of the vortex diffusion in the kHz regime, or analogously a strong reduction of the length scale probed by the incoming finite-frequency field. This effect suggests the emergence of an intrinsic length scale for the vortex motion that coincides with the typical size of inhomogeneity probed by STM measurements in disordered NbN films.

Competition between electron pairing and phase coherence in superconducting interfaces

“…In superconducting thin films, J s is usually assessed either from penetration depth measurements 16 , 17 or from dynamic transport measurements 18 , 19 . This latter method was adapted in this work for the specific case of LaAlO 3 /SrTiO 3 samples.…”

Evidence for correlated dynamics near the Berezinskii-Kosterlitz-Thouless-like transition in highly underdopedLa2−xSrxCuO4

“…[21] and [22], respectively), but not for correlations. Also, in complex impedance studies, disorder-induced inhomogeneity may lead to spurious effects at low f [23], and magnetic flux noise is more susceptible to surface [24] and geometrical [25] effects. In contrast, R noise has been a powerful probe of correlated dynamics in many systems [26][27][28][29][30], including lightly doped, insulating LSCO [31,32].…”

Effective two-dimensional thickness for the Berezinskii-Kosterlitz-Thouless-like transition in a highly underdopedLa2−xSrxCuO4

“…(10) the temperature dependence of the superfluid stiffness J s (T ), which we analyze along the lines of the approach discussed earlier for both conventional 14,33,63,64 and cuprate superconductors.…”