Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · cond-mat/0007510

Angular dependence of the penetration depth in unconventional superconductors

Klaus Halterman·Oriol T. Valls·Igor Zutic
View original source ↗Read source document ↗Export metadata ↓

Abstract

We examine the Meissner state nonlinear electrodynamic effects on the field and angular dependence of the low temperature penetration depth, $λ$, of superconductors in several kinds of unconventional pairing states, with nodes or deep minima (``quasinodes'') in the energy gap. Our calculations are prompted by the fact that, for typical unconventional superconducting material parameters, the predicted size of these effects for $λ$ exceeds the available experimental precision for this quantity by a much larger factor than for others. We obtain expressions for the nonlinear component of the penetration depth, $Δλ$, for different two- and three- dimensional nodal or quasinodal structures. Each case has a characteristic signature as to its dependence on the size and orientation of the applied magnetic field. This shows that $Δλ$ measurements can be used to elucidate the nodal or quasinodal structure of the energy gap. For nodal lines we find that $Δλ$ is linear in the applied field, while the dependence is quadratic for point nodes. For layered materials with $\rm{YBa_2Cu_3O_{7-δ}}$ (YBCO) type anisotropy, our results for the angular dependence of $Δλ$ differ greatly from those for tetragonal materials and are in agreement with experiment. For the two- and three- dimensional quasinodal cases, $Δλ$ is no longer proportional to a power of the field and the field and angular dependences are not separable, with a suppression of the overall signal as the node is filled in.

Explore related subjects

cond-mat.supr-con

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Klaus Halterman, Oriol T. Valls, Igor Zutic. 2000-07-31. Angular dependence of the penetration depth in unconventional superconductors. https://doi.org/10.1103/physrevb.63.014501

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Anisotropic upper critical field in the van der Waals superconducting quasicrystal (Ta$_{0.7}$Nb$_{0.3}$)$_{1.6}$Te

We investigated the upper critical field of a large single grain of the Nb-substituted van der Waals layered quasicrystal (Ta$_{0.7}$Nb$_{0.3}$)$_{1.6}$Te. The sample exhibits a sharp superconducting transition at $T_{\mathrm{c}}$ = 1.35 K, the highest value reported to date among quasicrystal superconductors. The angular dependence of the critical field exhibits a pronounced criterion dependence: the field determined using the 10% $R_{\mathrm{N}}$ ($R_{\mathrm{N}}$: normal-state resistance) criterion is well described by the anisotropic Ginzburg-Landau model, whereas those determined using the 65% and 90% $R_{\mathrm{N}}$ criteria exhibit Tinkham-like angular dependence characteristic of two-dimensional superconductivity. The high-field part of the resistive transition is well described by a surface-superconductivity model and exhibits a pronounced excitation-current dependence for magnetic fields close to the $ab$ plane, supporting the presence of surface superconductivity on the quasiperiodic $ab$-plane surfaces. The bulk $H_{\mathrm{c2}}$ is strongly anisotropic, with the in-plane $H_{\mathrm{c2}}$ exceeding the weak-coupling Pauli limit by a factor of approximately 2.5. For both field orientations, $H_{\mathrm{c2}}(T)$ deviates upward from the conventional dirty-limit Werthamer-Helfand-Hohenberg prediction at low temperatures. A phenomenologically modified Ginzburg-Landau-Abrikosov-Gorkov model incorporating a spatial distribution of the electronic diffusivity substantially improves the description of $H_{\mathrm{c2}}(T)$, suggesting that spatial variations in electronic transport properties may contribute to its anomalous temperature dependence.

cond-mat.supr-con↗
arXiv2026

Field-induced incipient spin-density phase stabilized inside the nematic phase of FeSe$_{1-x}$S$_x$

Spin-density wave (SDW) order and superconductivity frequently compete and coexist in unconventional superconductors, where spin fluctuations often mediate superconducting pairing. In iron-chalcogenide superconductors, FeSe$_{1-x}$S$_x$, SDW order has only been detected under applied pressure, while both spin and nematic fluctuations are involved in determining their rich superconducting phase diagrams. Here, we report evidence for an incipient SDW phase, within the nematic state of FeSe$_{1-x}$S$_x$, revealed in magnetic fields up to 68~T. Once superconductivity is quenched, we observe sharp upturns in longitudinal resistivity accompanied by anomalies in tunnel diode oscillator frequency response and torque anisotropy, consistent with a field-induced electronic order. Dominant low-frequency quantum oscillations reveal a small reconstructed Fermi surface, consistent with a field-induced SDW order. Direct experimental comparisons with a pressure-tuned nematic, analogue, FeSe$_{0.96}$S$_{0.04}$, demonstrate that SDW phases are stabilized within the nematic phase of FeSe$_{1-x}$S$_x$ via both chemical substitution and applied pressure. These findings reveal that by weakening nematicity, the SDW orders are stabilised, which promotes the dominant superconducting pairing mechanism in iron chalcogenides.

cond-mat.supr-con↗
arXiv2026

Q-ball mechanism of electron transport and spin/phonon excitations properties of high-Tc superconductors

The Q-ball mechanism of high Tc superconductivity in cuprates, recently proposed by the author, is farther explored. Scattering on the Q-balls above Tc causes linear with temperature growth of electrical resistivity, splitting of the inplane phonon brunches into softened and hardened ones and hourglass dispersion of spin-wave excitations close to CDW and SDW wave vectors respectively. The diamagnetic response of Q-balls gas above Tc is in qualitative accord with experimental data in high Tc cuprates.

cond-mat.supr-con↗