Crossover from 2D to 3D behavior in the superfluid density of thin YBa2Cu3O7−δ films

Superconductor-to-metal quantum phase transition in overdoped La2−xSrxCuOLemberger1, Hetel2, Tsukada3 et al. 2011Phys. Rev. B

“…Analogous features appear in microwave measurements of σ in underdoped LSCO films [22], indicating significant interlayer coupling across the LSCO phase diagram. Finally, similar evidence for interlayer coupling is found in "thick" underdoped YBCO films, which also show 3D critical scaling [23].…”

Simultaneous suppression of superfluid and resistance on approach to superconductor-insulator transition in underdoped ultrathinCa0.3Y0.7Ba2Cu3Steers1, Lemberger2, Draskovic3 2016Phys. Rev. B8010View full textAdd to dashboardCite

“…We have grown 10 uc films with T c 's up to 75 K, while we have grown 5 uc films with T c 's up to 60 K and 2 uc films with T c 's up to 40 K. We pause to consider how we should treat the dimensionality of our films. Previous measurements find that the expected drop in superfluid density at the Kosterlitz-Thouless-Berezinskii transition occurs at a temperature consistent with the interpretation that copper-oxide layers are sufficiently coupled that the full film thickness behaves as a single two-dimensional film 14 . This is puzzling from a theoretical side, for at T = 0, the c-axis coherence length for YBCO, ξ , is approximately 4 Angstroms, less than the c-axis unit cell dimension of 11.8 Angstroms.…”

“…Figure (2) shows the superfluid density and resistivity ρ in the vicinity of the transition to superconductivity for a film that is 50 unit cells thick, totalling 59 nm. For our pur- poses, this is a thick film 14 . As one would expect from crystals and other studies on 'thick' (20 to 100 uc) films, the resistive and superfluid transitions are fairly close in temperature.…”

Covariant gaussian approximation in Ginzburg–Landau model

“…(9) as a perturbation. The minimization equation (12) can be interpreted variationally as minimizing the quantum mechanical double well Hamiltonian…”

“…Superconducting fluctuations as far above T c as 2T c still dominate over the normal state contributions to the above three physical phenomena. Similarly below T c (but away from low temperatures where the penetration depth is mainly determined by its microscopic details) the fluctuations strongly affect the nontrivial penetration depth dependence on temperature [10][11][12] and magnetic properties [4]. In particular some of the still poorly understood phenomena in underdoped and optimally doped high T c cuprates known as the ''pseudogap'' features [13] can be interpreted as strong fluctuations effects that are nonperturbative [14] (cannot be accounted for by gaussian fluctuations) rather than stemming from an yet unknown microscopic origin.…”