Anisotropy of 2H-NbSe_(2)in the superconducting and charge density wave states  

作　　者：张驰 乔山 肖宏 胡涛 Chi Zhang;Shan Qiao;Hong Xiao;Tao Hu(State Key Laboratory of Functional Materials for Informatics,Shanghai Institute of Microsystem and Information Technology,Chinese Academy of Sciences,Shanghai 200050,China;Beijing Academy of Quantum Information Sciences,Beijing 100193,China;Center for High Pressure Science and Technology Advanced Research,Beijing 100094,China;CAS Center for Excellence in Superconducting Electronics(CENSE),Shanghai 200050,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]State Key Laboratory of Functional Materials for Informatics,Shanghai Institute of Microsystem and Information Technology,Chinese Academy of Sciences,Shanghai 200050,China [2]Beijing Academy of Quantum Information Sciences,Beijing 100193,China [3]Center for High Pressure Science and Technology Advanced Research,Beijing 100094,China [4]CAS Center for Excellence in Superconducting Electronics(CENSE),Shanghai 200050,China [5]University of Chinese Academy of Sciences,Beijing 100049,China

出　　处：《Chinese Physics B》2023年第4期593-597,共5页中国物理B（英文版）

基　　金：Project supported by the National Natural Science Foundation of China(Grant Nos.11574338 and 12074038);NSAF(Grant No.U1530402)。

摘　　要：Anisotropy is an important feature of layered materials,and a large anisotropy is usually related to the two-dimensional charac teristics.We investigated the anisotropy of the layered transition metal dicalcogenide 2H-NbSe_(2)in the superconducting and charge density wave(CDW)states using magnetotransport measurements.In the superconducting state,the normalized H_(c2)^(‖c)/H_(p)is independent of the thickness of 2H-NbSe_(2),while H_(c2)^(‖ab)/H_p increases significantly with decreasing thickness,where H_p is the Pauli limiting magnetic field and H_(c2)^(‖c)anu H_(c2)^(‖ab)are the upper critical fields in the c and ab directions,respectively.It is found that the superconducting anisotropy parameterγH_(c2)=H_(c2)^(‖ab)/H_(c2)^(‖c)increases with reduction in the thickness of 2H-NbSe_(2).In the CDW state,the angular(θ)dependence of magnetoresistance,R(H,θ)scales with H(cos^(2)θ+γ_(CDW)^(-2)sin^(2)θ)^(1/2),which decreases with increasing temperature and disappears at about 40 K.It is found that the CDW anisotropy parameterγ_(CDW)is much larger than the effective mass anisotropy but does not change a lot for ultrathin and bulk samples.Our results suggest the existence of three-dimensional superconductivity and quasi-two dimensional CDWs in bulk 2H-NbSe_(2).

关 键 词：ANISOTROPY SUPERCONDUCTIVITY charge density wave transition metal dicalcogenides 

分 类 号：O469[理学—凝聚态物理]