Thermodynamic study and intrinsic type II superconductivity in the A-15 compound V3Si

Abstract

The specific heat of a single crystal of the A-15-type compound V3Si in the normal, mixed, and superconducting states has been measured from 4 to 30 K in magnetic fields up to 50 kOe. The analysis has been performed in a self-consistent way based on the second-order phase transition from the normal to the superconducting state. The thermodynamic critical field and then various physical parameters characterizing the superconducting and normal states are almost consistently derived from the thermodynamics and the microscopic BCS-GLA G theory. It is confirmed that V3Si is an intrinsic type H superconductor with a high intrinsic GL parameter Ko.

Strong electron-phonon coupling in the rare-earth carbide superconductorLa2C3

“…A sharp anomaly at ≈ 13.4 K is clearly resolved indicating bulk superconductivity in the La 2 C 3 sample, which has not been observed previously. 44 The onset of 13.4 K determined from the specific heat jump is consistent with that obtained from the susceptibility measurements. At H = 9 T, the superconducting anomaly is shifted to lower temperatures.…”

“…4 is the best fit to the H = 9 T data for T c (H = 9 T) < T < 15 K, yielding the parameters, γ N = 10.60(4) mJ/mol K 2 , β = 228.2(11) µJ/mol K 4 , and δ = 0.5988 µJ/mol K 6 . The measured γ N is much higher and more realistic than those previously reported from specific heat 44 and upper critical fields measurements. 12 The corresponding Debye temperature Θ D (0) = 349(1) K is comparable with that found in previous work.…”

Experimental determination of the temperature-dependent penetration depth in V/sub 3/Si

“…The result of such a fit is shown in Figure 2, where we have included the combined effects of strong-coupling and impurity scatterina. From this we obtain, agree with, but lie near the upper range of, previous determinations found by a variety of experimental techniques (4)(5)(6).…”

“…From the measured value at low-temperature (see Figure 1), we obtain the London penetration depth X L (0) =A(0)(l+1.283Q)-i /2 =91.6±2. 5 nm, slightly larger than that calculated from normal state properties, which yield AjJO) in the range 75 nm to 86 nm (4,5). The value XL BCi (0)=57nm, found using unrenormalized properties calculated from band theory (6), would imply an anomalously large electron-phonon coupling constant A e p=1.6.…”

Microavalanches Size Distribution in Fine Structure of Thermomagnetic Flux Jumps in the V3Si Monocrystal Superconductor

“…Unfortunately, it was not possible to answer definitely the question of the nature of the pinning centers in our sample. According to the value of the resistance ratio (R 300 K /R 20 K ≈ 12) we have that the mean free path is estimated to be as long as the Ginzburg-Landau coherence length l ≈ ξ G−L [14] that is, our sample is in the middle between the limits of pure l ξ and a dirty superconductor l ξ. The investigated crystal is quite perfect from the crystallographic point of view, which was confirmed by the X-ray studies.…”