Effect of Nonmagnetic Impurities on the Electronic State of Quasiparticles Confined in the Naturally Prepared Nanostructure under Magnetic Field in YBa₂Cu₃O_y

Abstract

The effects of Zn impurities on the electronic state in the vortex core were investigated systematically in almost optimally doped YBa 2 (Cu 1Àx Zn x ) 3 O y (0 x 0:06) using the microwave complex surface impedance (Z s ) measurement technique. We estimated the viscosity, , and the pinning constant, p , of a vortex as functions of temperature and x on the basis of a mean-field theory of the vortex motion. p as a function of Zn concentration, x, suggests that Zn doping is not an effective procedure for pinning the vortex motion. ðxÞ depended very weakly on x for x 0:003, while it decreased rapidly with increasing x for x > 0:003. These finding suggest that the scattering of QPs in the vortex core is much larger than that in the Meissner (zero-field) state for x 0:003. On the other hand, for x > 0:003, the scattering of QPs in the vortex core is governed by Zn impurity, showing that the presence of the vortex is not important for the scattering in this regime. The large scattering in the low-doping-concentration region (x 0:003) is particularly important, since this is characteristic of the presence of the vortex core. Our result is consistent with the previously published microwave result for the Zn-free material [Tsuchiya et al.: Phys. Rev. B 63 (2001) 184517] in the sense that both experimental data suggest the existence of the high QP-DOS in the vortex core, but is inconsistent with a picture proposed by STM measurements on the vortex core. We discuss possible origins for this discrepancy, including novel mechanisms of energy dissipation in the motion of a moderately clean (' $ ) vortex core.

Low energy excitations inside the vortex core of LiFe(As, P) single crystals investigated by microwave-surface impedance

“…In other words, the mean free path of quasi-particles inside the vortex core, l core = v F s core % 200 Å is much shorter than that outside by one order of magnitude, and is rather comparable to the core radius, n % 40 Å, where v F % 3.5 Â 10 4 m/s is the Fermi velocity estimated from the relation hx 0 ¼ D 0 =k F n. This tendency seems to be very strange at the first sight. However, the short mean free path of the quasi-particle inside the vortex core was also observed in the flux-flow study of cuprate superconductors [11,[29][30][31] and Y 2 C 3 [32]. In the cuprate case, the mean free path inside the vortex core is also much shorter than that outside and close to the core radius, l core $ n ( l M .…”

Vortex dynamics in a NbN film studied by terahertz spectroscopy

“…28͒, or in high-T c SCs. 13,29 In the present case of NbN, however, the system can be recognized as dirty limit. In such a case, the bound states in the vortex core are considered to disappear and the conductivity inside the vortex can be regarded as that of normal state.…”

“…10͒ and at 10-100 GHz for high-T c SCs, 11 the high-frequency electromagnetic response of vortices has been intensively studied. [10][11][12][13][14] With the progress of terahertz time-domain spectroscopy ͑THz-TDS͒, 15 the energy range has been further extended, making it possible to obtain directly the complex conductivity spectra without using Kramers-Kronig analysis. Especially, since the relevant frequency is much higher than the depinning frequency even for high-T c SCs, the technique makes it possible to obtain the resistivity in the flux-flow region by optical means.…”

Study of friction using driven vortices of superconductor as a model system

“…With an aid of a general phenomenological model [33], we can extract fluxflow resistivity. Details on the procedure were described in the literatures [31,32,34].…”

“…We can know both j and ρ by the usual dc I-V characteristics measurement, whereas ρ ∞ can be obtained in the microwave complex surfaceimpedance measurement [31,32].…”