Hole-doping dependence of the magnetic penetration depth and vortex core size inYBa2Cu3Oy: Evidence for stripe correlations near

Abstract

We report on muon spin rotation (µSR) measurements of the internal magnetic field distribution n(B) in the vortex solid phase of YBa2Cu3Oy (YBCO) single crystals, from which we have simultaneously determined the hole doping dependences of the in-plane Ginzburg-Landau (GL) length scales in the underdoped regime. We find that Tc has a sublinear dependence on 1/λ 2 ab , where λ ab is the in-plane magnetic penetration depth in the extrapolated limits T → 0 and H → 0. The power coefficient of the sublinear dependence is close to that determined in severely underdoped YBCO thin films, indicating that the same relationship between Tc and the superfluid density is maintained throughout the underdoped regime. The GL coherence length ξ ab (vortex core size) is found to increase with decreasing hole doping concentration, and exhibit a field dependence that is explained by proximity-induced superconductivity on the CuO chains. Both λ ab and ξ ab are enhanced near 1/8 hole doping, supporting the belief by some that stripe correlations are a universal property of high-Tc cuprates.

Role of CuO chains in vortex core structure inYBa2Cu3O7−δ

“…5 are in qualitative agreement with a simplified quasiclassical "doppler-shift" calculation that has been reported previously 12 . The current results confirm the validity of the previous approximate calculations.…”

“…Experimental measurements of the core size 12 , plotted in Fig. 5(c), show a similar variation at low field.…”

“…2(a,b) have a radius of roughly 2a 0 , whereas the coherence length is ∼ 5a 0 in optimally-doped YBCO 6.95 . 12 This discrepancy results from our having taken the order parameter to be twice what is appropriate for quantitative models of YBa 2 Cu 3 O 7−δ . We have done this so that energy scale of the the induced gap in the chain layer lies near the middle of the range of numerically accessible magnetic fields.…”

The effect of CuO chains on the local density of states in the vortex phase of YBa2Cu3O7

“…For example, it has been found [16,17] that the vortex cores in YBa 2 Cu 3 O 7−δ , as measured by µSR experiments, are much larger at small magnetic fields B than expected from the measured upper critical field, and that the cores contract rapidly with increasing B below a crossover field B * . This anomalous behaviour has been explained by the presence of CuO chains [18,19], and it can be shown that B * ∼ E 2 s . It has also been suggested that a similar small energy scale seen in tunneling experiments [20,21,22] can be attributed to the chains.…”

Response of HTS tapes to a parallel ac magnetic field in the vicinity of the superconducting transition

“…However, this refined method is labor-consuming (e.g., the study in Ref. 7 was performed during several years). Moreover, the SR method is used to measure the magnetic field distribution in superconductors in the vortex state.…”