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Register a new userStrong pressure dependence of the magnetic penetration depth in single crystals of the heavy fermion superconductor CeCoIn5 studied by muon spin rotation
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In the tetragonal heavy fermion system CeCoIn5 the unconventional superconducting state is probed by means of muon spin rotation. The pressure dependence (0-1 GPa) of the basal-plane magnetic penetration depth (lambda_a), the penetration depth anisotropy (gamma=lambda_c/lambda_a) and the temperature dependence of 1/lambda_i^2 (i=a,c) were studied in single crystals. A strong decrease of lambda_a with pressure was observed, while gamma and lambda_i^2(0)/lambda_i^2(T) are pressure independent. A linear relationship between 1/lambda_a^2(270 mK) and Tc was also found. The large decrease of lambda_a with pressure is the signature of an increase of the number of superconducting quasiparticles by a factor of about 2.
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We report temperature- and magnetic field-dependent bulk muon spin rotation measurements in a c-axis oriented superconductor CaC6 in the mixed state. Using both a simple second moment analysis and the more precise analytical Ginzburg-Landau model, we obtained a field independent in-plane magnetic penetration depth {lambda}ab (0) = 72(3) nm. The temperature dependencies of the normalized muon spin relaxation rate and of the normalized superfluid density result to be identical, and both are well represented by the clean limit BCS model with 2Delta/kB Tc = 3.6(1), suggesting that CaC6 is a fully gapped BCS superconductor in the clean limit regime.
The pressure dependence of the magnetic penetration depth in polycrystalline samples of YBa2Cu3Ox with different oxygen concentrations x = 6.45, 6.6, 6.8, and 6.98 was studied by muon spin rotation (muSR). The pressure dependence of the superfluid density (p_s) as a function of the superconducting transition temperature Tc is found to deviate from the usual Uemura line. The ratio (dTc/dP)/(dp_s/dP) is factor of 2 smaller than that of the Uemura relation. In underdoped samples, the zero temperature superconducting gap and the BCS ratio both increase with increasing external hydrostatic pressure, implying an increase of the coupling strength with pressure. The relation between the pressure effect and the oxygen isotope effect on the magnetic penetration depth is also discussed. In order to analyze reliably the muSR spectra of samples with strong magnetic moments in a pressure cell, a special model was developed and applied.
We report transverse field and zero field muon spin rotation studies of the superconducting rhenium oxide pyrochlore, Cd2Re2O7. Transverse field measurements (H=0.007 T) show line broadening below Tc, which is characteristic of a vortex state, demonstrating conclusively the type-II nature of this superconductor. The penetration depth is seen to level off below about 400 mK (T/Tc~0.4), with a rather large value of lambda (T=0)~7500A. The temperature independent behavior below ~ 400 mK is consistent with a nodeless superconducting energy gap. Zero-field measurements indicate no static magnetic fields developing below the transition temperature.
The temperature dependence of the in-plane, lambda_{parallel}, and interplane, lambda_{perp}, London penetration depth was measured in the metal-free all-organic superconductor beta-ET (see title) ($T_c approx$ 5.2 K). lambda_{parallel} ~T^3 up to 0.5 Tc, a power law previously observed only in materials thought to be p-wave superconductors. lambda_{perp} is larger than the sample dimensions down to the lowest temperatures (0.35 K), implying an anisotropy of lambda_{perp}/lambda_{parallel} ~ 400-800.
Muon-spin rotation spectroscopy has been used to measure the internal magnetic field distribution in NbSe2 for Hc1 << H < 0.25 Hc2. The deduced profiles of the supercurrent density indicate that the vortex-core radius in the bulk decreases sharply with increasing magnetic field. This effect, which is attributed to increased vortex-vortex interactions, does not agree with the dirty-limit microscopic theory. A simple phenomenological equation in which the core radius depends on the intervortex spacing is used to model this behaviour. In addition, we find for the first time that the in-plane magnetic penetration depth increases linearly with H in the vortex state of a conventional superconductor.
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