中国物理B ›› 2008, Vol. 17 ›› Issue (6): 2229-2235.doi: 10.1088/1674-1056/17/6/048

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Quasiparticle density of states of 2H-NbSe2 single crystals revealed by low-temperature specific heat measurements according to a two-component model

肖志力1, 闫静2, 单磊2, 王越2, 闻海虎2   

  1. (1)Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA;Department of Physics, Northern Illinois University, DeKalb, Illinois 60115, USA; (2)National Laboratory for Superconductivity, Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190, China
  • 收稿日期:2008-02-28 修回日期:2008-03-07 出版日期:2008-06-20 发布日期:2008-06-20
  • 基金资助:
    Project supported by the National Natural Science Foundation of China(Grant Nos 10221002/A0402 and 10774170/A0402), the State Key Development for Basic Research of China (Grant Nos 2006CB601000, 2006CB921802 and 2006CB921300), the Knowledge Innovation Pro

Quasiparticle density of states of 2H-NbSe2 single crystals revealed by low-temperature specific heat measurements according to a two-component model

Yan Jing(闫静)a), Shan Lei(单磊)a), Wang Yue(王越)a), Xiao Zhi-Li(肖志力)b)c), and Wen Hai-Hu(闻海虎)a)†   

  1. a  National Laboratory for Superconductivity, Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190, China; b Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA; b Department of Physics, Northern Illinois University, DeKalb, Illinois 60115, USA
  • Received:2008-02-28 Revised:2008-03-07 Online:2008-06-20 Published:2008-06-20
  • Supported by:
    Project supported by the National Natural Science Foundation of China(Grant Nos 10221002/A0402 and 10774170/A0402), the State Key Development for Basic Research of China (Grant Nos 2006CB601000, 2006CB921802 and 2006CB921300), the Knowledge Innovation Pro

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摘要： 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 concerning 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 $\gamma(H)$, 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.

关键词: 2H-NbSe2, charge density wave, superconductivity, specific heat

Abstract: 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 concerning 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 $\gamma(H)$, 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.

Key words: 2H-NbSe2, charge density wave, superconductivity, specific heat

中图分类号:  (Electronic structure (photoemission, etc.))

  • 74.25.Jb
74.20.Fg (BCS theory and its development) 74.25.Bt (Thermodynamic properties)