Thermodynamic properties of the layered superconductor 2H-NbSe/sub 2/

Journal Article · Fri Apr 01 04:00:00 EST 1977 · J. Low Temp. Phys.; (United States)

DOI:https://doi.org/10.1007/BF00654647· OSTI ID:7220146

Kobayashi, N; Noto, K; Muto, Y

The specific heat in the normal and superconducting states of single crystals of the transition metal dichalcogenide superconductor 2H-NbSe/sub 2/ was measured from 1.7 to 9 K by use of a thermal relaxation method. The thermodynamic critical field and the specific heat behavior are different from those predicted by the BCS theory. The anisotropy and strong coupling effects in the thermodynamic properties are made evident through comparison wilth the Clem--Sheahen--Gubser relations, which take account of these effects near T/sub c/ and 0 K. A simple semiempirical model is proposed to explain the temperature dependences of the thermodynamic critical field and the superconducting electronic specific heat. Under the assumption of a spheroidal Fermi surface based on the tight-binding approximation, the model takes into account effects of the anisotropy and the strong coupling interaction in the expression for the energy gap ..delta../sub g/k(t) =K/sub 0/(t)(1+epsilon/sub 2/cos/sup 2/theta). The strong coupling parameter 2..delta../sub 0/(0)/k/sub B/T/sub c/ and the energy gap anisotropy parameter epsilon/sub 2/ are the only two adjustable parameters. The thermodynamic behavior deduced from the model gives good agreement with experimental results for values of 2..delta../sub 0/(0)/k/sub B/T/sub c/approx. =5.0 and epsilon/sub 2/approx. =--0.6.

• Research Organization: The Research Institute for Iron, Steel and Other Metals, Tohoku University, Sendai, Japan
• OSTI ID: 7220146
• Journal Information: J. Low Temp. Phys.; (United States), Journal Name: J. Low Temp. Phys.; (United States) Vol. 27:1; ISSN JLTPA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360104* -- Metals & Alloys-- Physical Properties
656102 -- Solid State Physics-- Superconductivity-- Acoustic
Electronic
Magnetic
Optical
& Thermal Phenomena-- (-1987)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANISOTROPY
BCS THEORY
CHALCOGENIDES
CRITICAL FIELD
CRYSTALS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
MAGNETIC FIELDS
MONOCRYSTALS
NIOBIUM COMPOUNDS
NIOBIUM SELENIDES
PHYSICAL PROPERTIES
SELENIDES
SELENIUM COMPOUNDS
SPECIFIC HEAT
SUPERCONDUCTIVITY
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE
ULTRALOW TEMPERATURE