Specific heat of Nb_3Sn: The case for a second energy gap

Abstract

We present new specific heat data for Nb3Sn, a well-known technically applied superconductor with a critical temperature T_c ~ 18 K, in the temperature range from 1.2 to 200 K in zero magnetic field, and from 1.5 to 22 K in fields H <= 16 T. The particularly dense and homogeneous polycrystalline sample used for this study is characterized in detail. We determine the bulk upper critical field H_c2(T) from specific heat data, and the Sommerfeld constant Gamma from the entropy S(T). We investigate in detail a low-temperature anomaly already noticed in previous investigations in zero field, and find that this feature can be quantitatively ascribed to the presence of a second superconducting gap 2 Delta_S(0) ~ 0.8 k_B T_c, in addition to the main one 2 Delta_L(0) ~ 4.9 k_B T_c. The signature of this minor gap, which affects 7.5% of the electronic density-of-states, vanishes in fields above ~ 7 T.

16 pages, 8 figures

References in corpus (8)

• Beyond Eliashberg superconductivity in MgB2: anharmonicity, two-phonon scattering, and multiple gaps
• Two-gap superconductivity in MgB${}_2$: clean or dirty?
• Phenomenological two-gap model for the specific heat of MgB_2
• Upper critical field pecularities of superconducting YNi2B2C and LuNi2B2C
• Vortex Imaging in the pi-Band of Magnesium Diboride
• Unusual effects of anisotropy on the specific heat of ceramic and single crystal MgB2
• Nonconstant electronic density of states tunneling inversion for A15 superconductors: Nb3Sn
• The gap maximum of anisotropic superconductors

Cited by in corpus (36)

• A Review of the Properties of Nb3Sn and Their Variation with A15 Composition, Morphology and Strain State
• A general scaling relation for the critical current density in Nb3Sn
• Limits of the upper critical field in dirty two-gap superconductors
• Extremely strong-coupling superconductivity and anomalous lattice properties in the beta-pyrochlore oxide KOs2O6
• A review of two-band superconductivity: materials and effects on the thermodynamic and reversible mixed-state properties
• Doping evolution of superconducting gaps and electronic densities of states in Ba(Fe1-xCox)2As2 iron pnictides
• Rattling-Induced Superconductiviy in the Beta-Pyrochlore Oxides AOs2O6
• Specific heat evidence for two-gap superconductivity in ternary-iron silicide Lu${}_2$Fe${}_3$Si${}_5$
• Experimental evidence for a two-gap structure of superconducting NbSe_2: a specific heat study in external magnetic fields
• Pyrochlore Oxide Superconductor Cd2Re2O7 Revisited
• Thermodynamic origin of the peak effect in the superconductor Nb3Sn
• Phonon density of states, anharmonicity, electron-phonon coupling and possible multigap superconductivity in the clathrate superconductors Ba8Si46 and Ba24Si100: Why is Tc different in these two compounds?
• Microwave Response of V3Si Single Crystals: Evidence for Two-Gap Superconductivity
• Thermal fluctuations and vortex melting in the classical superconductor Nb3Sn from high-resolution specific-heat measurements
• Strain sensitivity and superconducting properties of Nb3Sn from first principles calculations
• Multi-band conductivity and multi-gap superconductivity in V3Si from optical measurements on films at terahertz frequencies
• Superconductivity at 3.7 K in Ternary Silicide Li2IrSi3
• The single- vs. two-gap scenario: the specific heat and the thermodynamic critical field of BeAu superconductor
• Evidence of multiband superconductivity in the $\beta$-phase Mo${}_{1-x}$Re${}_x$ alloys
• Muon spin rotation study of type-I superconductivity: elemental $\beta -$Sn
• Superconductivity in the Topological Nodal-line Semimetal NaAlSi
• Quantifying nonadiabaticity in major families of superconductors
• A theory of the strain-dependent critical field in Nb3Sn, based on anharmonic phonon generation
• Superconducting properties variation with A15 composition in Nb3Sn
• Universal Scaling Law for the Condensation Energy, U, Across a Broad Range of Superconductor Classes
• Testing V3Si for two-band superconductivity
• Nonlinear current response of one- and two-band superconductors
• Self-consistent two-gap approach in studying multi-band superconductivity in NdFeAsO${}_{0.65}$F${}_{0.35}$
• A second superconducting energy gap of Nb_3Sn observed by breakjunction point-contact spectroscopy
• Magnetic field-induced quasiparticle excitation in Nb3Sn: Evidence for anisotropic s-wave pairing
• Specific heat studies of pure Nb3Sn single crystals at low temperature
• Features of Excess Conductivity Behavior in a Magnetic Superconductor Dy${}_{0.6}$Y${}_{0.4}$Rh${}_{3.85}$Ru${}_{0.15}$B${}_4$
• Superconductivity in Nb5Ir3-xPtxO
• Investigate the effect of anisotropic order parameter on the specific heat of anisotropic two-band superconductors
• Abrikosov flux-lines in two-band superconductors with mixed dimensionality
• Differential-thermal analysis around and below the critical temperature Tc of various low-Tc superconductors: A comparative study