We have investigated the superconductivity and electronic state in FeSe1-xTex (0.6 ≦ x ≦ 1) from the specific heat measurements, using annealed single-crystals of good quality. First, it has been found that annealed single-crystals of x = 0.6-0.9 exhibit bulk superconductivity with a clear specific-heat jump at the superconducting (SC) transition temperature, Tc. Both 2Δ0/k BTc [Δ0: the SC gap at 0 K] and Δ C/(γn-γ0)Tc [Δ C: the specific-heat jump at Tc, γn: the electronic specific-heat coefficient in the normal state, γ0: the residual electronic specific-heat coefficient at 0 K in the SC state] are largest at x = 0.7 and are 4.29 and 2.38, respectively, indicating that the superconductivity is strong-coupling. Secondly, it has been found that the γn value is much larger than that estimated from the band calculation and increases with increasing x and suddenly decreases above x = 0.9 due to the antiferromagnetic ordering around x = 1. The large value of γn is guessed to be due to the enhancement of the effective mass related to spin fluctuation and/or orbital fluctuation. Finally, it has been found that there remains a finite value of the electronic specific-heat coefficient at 0 K even in the SC state at x = 0.8-0.9. This suggests that a phase separation into SC and normal-state regions takes place at x = 0.8-0.9. Otherwise, there might remain a normal-state pocket at the Fermi surface even in the SC state.
|ジャーナル||Journal of Physics: Conference Series|
|出版ステータス||Published - 2012|
|イベント||26th International Conference on Low Temperature Physics, LT 2011 - Beijing, China|
継続期間: 2011 8 10 → 2011 8 17
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