measurements on the vortex lattice of La1.83Sr0.17CuO4

Experimental Evidence for Two Gaps in the High-TemperatureLa1.83Sr0.17CuO4Superconductor

“…The analysis reveals for "d + s": ∆ [21], suggests that the large gap has d−wave symmetry. Another argument in favor of a "large" d−wave gap comes from the observation of a square vortex lattice in the same crystal as used in this work in fields higher than 0.4 T [14,22], where as shown below the contribution from the large gap to σ sc is dominant. A square vortex lattice is typical for d−wave superconductors [14].…”

Concerning the superconducting gap symmetry in YBa2Cu3O7 − δ, YBa2Cu4O8, and La2 −xSrxCuO4determined from muon spin rotation in mixed states of crystals and powders

“…However, as noted in [14] such asymmetry in P(B) is consistent with pinning. In actuality, the deviations observed [41] in the high-field tail of the local magnetic field distribution are most certainly due to field-induced changes in the pinning structure, and a symmetric lineshape is only observed with vortex melting at T ≈ 30 K (the single-crystal La 1.83 Sr 0.17 CuO 4 sample studied in [41] was the same sample measured earlier by different groups [62,63]). Even for static pinning, lineshapes depend upon the structure of the pinning potential [2], crystal stacking faults and the longitudinal flux line correlation length [33,35]; a symmetric and greatly narrowed lineshape is, for example, observed for Bi 2 Sr 2 CaCu 2 O 8+δ at 1.5 T (see figure 3 of [35]), and is attributable to a shortened hard-axis (longitudinal) correlation length.…”

“…a minor maximum at 0.1 T and a minimum at 0.45 T) [63] and YBa 2 Cu 3 O 7-δ [25,37]. This non-monotonic response is illustrated for La 1.83 Sr 0.17 CuO 4 in figure 6, where data obtained from [63] (reproduced as filled circles) show a markedly subdued and non-monotonic field dependence, when compared to the lesser complete data of [41] (triangles). The solid curve in figure 6 shows the depinning model for σ ab (T=0,H) at H = 0.02, 0.1, and 0.64 T and smooth interpolation for fields in between points.…”

“…The fit obtained for 0.2 T with the d-wave gap function is given by the dashed curve in figure 5(b), illustrating its deviation from the data. Data set "A" is taken from [41] and data set "B" is from [63]. The solid curve is the depinning model fitted to data "A"; dashed curve is for ideal flux lattice [44] (absent depinning effects) fitted to data "B".…”

Evidence for a square-square vortex lattice transition in a high-$T_\textrm{c}$ cuprate superconductor

“…Indeed, ultrasound has been used to observe a known 45 • rotation of the hexagonal vortex lattice and a rhombicsquare transition in YNi 2 B 2 C at low fields [31]. In LSCO p = 0.17, the VL structure goes from hexagonal to square at very low field (< 0.5 T) with nearest-neighbour direction aligned along the Cu-O directions [12,13,32]. This square VL configuration, presented as v in Fig.…”