,Quasiparticle density of states of 2H-NbSe2 single crystals revealed by low-temperature specific he

• 作 者: Yan Jing Shan Lei Wang Yue Xiao Zhi-Li Wen Hai-Hu
• 机 构: National Laboratory for Superconductivity, Institute of Physics and Beifing National Laboratory for
• 出 处: 中国物理B(英文版)
• 发表日期: 2008年6期
• 关键词: 2H-NbSe2 charge density wave superconductivity specific heat

Low-temperature specific heat in a dichalcogenide superconductor 2H-NbSe2 is measured in various magnetic fields. It is found that the specific heat can be described very well by a simple model conceing two components corresponding to vortex normal core and ambient superconducting region, separately. For calculating the specific heat outside the vortex core region, we use the Bardeen-Cooper-Schrieffer (BCS) formalism under the assumption of a narrow distribution of the superconducting gaps. The field-dependent vortex core size in the mixed state of 2H-NbSe2, determined by using this model, can explain the nonlinear field dependence of specific heat coefficient γ(H), which is in good agreement with the previous experimental results and more formal calculations. With the high-temperature specific heat data, we can find that, in the multi-band superconductor 2H-NbSe2, the recovered density of states (or Fermi surface) below Tc under a magnetic field seems not to be gapped again by the charge density wave (CDW) gap, which suggests that the superconducting gap and the CDW gap may open on different Fermi surface sheets.