TY - JOUR

T1 - Specific-heat study of superconducting and normal states in FeSe 1-xTe x (0:6 < x < 1) single crystals

T2 - Strong-coupling superconductivity, strong electron-correlation, and inhomogeneity

AU - Noji, Takashi

AU - Imaizumi, Masato

AU - Suzuki, Takumi

AU - Adachi, Tadashi

AU - Kato, Masatsune

AU - Koike, Yoji

PY - 2012/5

Y1 - 2012/5

N2 - The electronic specific heat of as-grown and annealed single-crystals of FeSe 1-xTe x (0:6 ≤ x ≤ 1) has been investigated. It has been found that annealed single-crystals with x = 0:6-0:9 exhibit bulk superconductivity with a clear specific-heat jump at the superconducting (SC) transition temperature, T c. Both Uδ 0=kBT c [Δ 0: the SC gap at 0K estimated using the single-band BCS s-wave model] and ΔC=(γ n =γ 0)T c [AC: the specific-heat jump at T c, γ n: the electronic specific-heat coefficient in the normal state, γ 0: the residual electronic specific-heat coefficient at 0K in the SC state] are largest in the well-annealed single-crystal with x = 0:7, i.e., 4.29 and 2.76, respectively, indicating that the superconductivity is of the strong coupling. The thermodynamic critical field has also been estimated. yn has been found to be one order of magnitude larger than those estimated from the band calculations and increases with increasing x at x = 0:6{0:9, which is surmised to be due to the increase in the electronic effective mass, namely, the enhancement of the electron correlation. It has been found that there remains a finite value of γ 0 in the SC state even in the well-annealed single-crystals with x = 0:8-0:9, suggesting an inhomogeneous electronic state in real space and/or momentum space.

AB - The electronic specific heat of as-grown and annealed single-crystals of FeSe 1-xTe x (0:6 ≤ x ≤ 1) has been investigated. It has been found that annealed single-crystals with x = 0:6-0:9 exhibit bulk superconductivity with a clear specific-heat jump at the superconducting (SC) transition temperature, T c. Both Uδ 0=kBT c [Δ 0: the SC gap at 0K estimated using the single-band BCS s-wave model] and ΔC=(γ n =γ 0)T c [AC: the specific-heat jump at T c, γ n: the electronic specific-heat coefficient in the normal state, γ 0: the residual electronic specific-heat coefficient at 0K in the SC state] are largest in the well-annealed single-crystal with x = 0:7, i.e., 4.29 and 2.76, respectively, indicating that the superconductivity is of the strong coupling. The thermodynamic critical field has also been estimated. yn has been found to be one order of magnitude larger than those estimated from the band calculations and increases with increasing x at x = 0:6{0:9, which is surmised to be due to the increase in the electronic effective mass, namely, the enhancement of the electron correlation. It has been found that there remains a finite value of γ 0 in the SC state even in the well-annealed single-crystals with x = 0:8-0:9, suggesting an inhomogeneous electronic state in real space and/or momentum space.

KW - Electronic specific-heat coefficient

KW - FeSe Te single crystal

KW - Specific heat

KW - Superconducting condensation energy

KW - Superconducting gap

KW - Thermodynamic critical field

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U2 - 10.1143/JPSJ.81.054708

DO - 10.1143/JPSJ.81.054708

M3 - Article

AN - SCOPUS:84860634678

VL - 81

JO - Journal of the Physical Society of Japan

JF - Journal of the Physical Society of Japan

SN - 0031-9015

IS - 5

M1 - 054708

ER -