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arXiv 0803.2948cond-mat.supr-concond-mat.str-el
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超导体Mo3Sb7的低温specific heat

Low-temperature specific heat of the superconductor Mo3Sb7

V. H. Tran, W. Miiller, Z. Bukowski

摘要:

在高达5 T的磁场中测量了Tc = 2.25(0.05)K的Mo_3Sb_7超导体的低温比热。在正常状态下,电子比热系数γ_n和德拜温度θ_D分别为34.5(2)mJ/molK^2和283(5)K。γ_n值的增加是由于Mo-4d带钉扎在费米能级上所致。超导态的电子比热可以用唯象的双BCS能隙模型来分析,其能隙宽度为2Delta_1/kBT_c = 4.0和2Delta_2/kBT_c = 2.5,摩尔电子热系数γ_1/γ_n = 0.7和γ_2/γ_n = 0.3。计算了该超导体的比热跃变Δ C_p(T_c)/γ_nT_c、电子-声子耦合常数λ_eph、上H_c2场和热力学临界H_c0场、穿透深度λ、相干长度xi和Ginzburg-Landau参数kappa。2Delta/kBT_c、DeltaC_p(T_c)/gamma_nT_c、N(E_F)和lambda_eph等参数的估计值表明,Mo_3Sb_7属于中等耦合区域。电子能带结构计算表明,费米能级附近的态密度主要由Mo-4d轨道形成,Mo- 4d轨道与Sb-sp轨道之间没有重叠。

英文摘要:

The low-temperature specific heat of a superconductor Mo3Sb7 with T_c = 2.25 (0.05) K has been measured in magnetic fields up to 5 T. In the normal state, the electronic specific heat coefficient gamma_n, and the Debye temperature Theta_D are found to be 34.5(2) mJ/molK^2 and 283(5) K, respectively. The enhanced gamma_n value is interpreted due to a narrow Mo-4d band pinned at the Fermi level. The electronic specific heat in the superconducting state can be analyzed in terms a phenomenological two BCS-like gap model with the gap widths 2Delta_1/k_BT_c = 4.0 and 2Delta_2/k_BT_c = 2.5, and relative weights of the mole electronic heat coefficients gamma_1/gamma_n = 0.7 and gamma_2/gamma_n = 0.3. Some characteristic thermodynamic parameters for the studied superconductor, like the specific heat jump at T_c, DeltaC_p(T_c)/gamma_nT_c, the electron-phonon coupling constant,lambda_eph, the upper H_c2 and thermodynamic critical H_c0 fields, the penetration depth, lambda, coherence length xi, and the Ginzburg-Landau parameter kappa are evaluated. The estimated values of parameters like 2Delta/k_BT_c, DeltaC_p(T_c)/gamma_nT_c, N(E_F), and lambda_eph suggest that Mo3Sb7 belongs to intermediate-coupling regime. The electronic band structure calculations indicate that the density of states near the Fermi level is formed mainly by the Mo-4d orbitals and there is no overlapping between the Mo- 4d and Sb-sp orbitals.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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