Superconductivity in chromium nitrides Pr3Cr10-xN11 with strong electron correlations  

作　　者：Wei Wu Kai Liu Yanjie Li Zhenhai Yu Desheng Wu Yuting Shao Shihang Na Gang Li Ruizhen Huang Tao Xiang Jianlin Luo 

机构地区：[1]Beijing National Laboratory for Condensed Matter Physics and Institute of Physics,Chinese Academy of Sciences,Beijing 100190,China [2]School of Physical Sciences,University of Chinese Academy of Sciences,Beijing 100190,China [3]Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials&Micro-nano Devices,Renmin University of China,Beijing 100872,China [4]School of Physical Science and Technology,ShanghaiTech University,Shanghai 201210,China [5]Songshan Lake Materials Laboratory,Dongguan 523808,China [6]Kavli Institute for Theoretical Sciences,Beijing 100190,China

出　　处：《National Science Review》2020年第1期21-26,共6页国家科学评论（英文版）

基　　金：supported by the National Basic Research Program of China(2017YFA0302901,2014CB921500);the National Natural Science Foundation of China(11674375,11634015);the Strategic Priority Research Program and Key Research Program of Frontier Sciences of the Chinese Academy of Sciences(XDB07020200)

摘　　要：Exploration of superconductivity in Cr-based compounds has attracted considerable interest because only a few Cr-based superconductors(CrAs,A2Cr3As3 and ACr3As3(A=K,Rb,Cs,Na))have been discovered so far and they show an unconventional pairing mechanism.We report the discovery of bulk superconductivity at 5.25 K in chromium nitride in Pr3Cr10-xN11 with a cubic lattice structure.A relatively large upper critical field of Hc2(0)~12.6 T is determined,which is larger than the estimated Pauli-paramagnetic pair-breaking magnetic field.The material has a large electronic specific-heat coefficient of 170 mJ K^-2mol^-1-about 10 times larger than that estimated by the electronic structure calculation,which suggests that correlations between 3d electrons are very strong in Pr3Cr10-xN11,and thus quantum fluctuations might be involved.Electronic structure calculations show that the density of states at the Fermi energy are contributed predominantly by Cr 3d electrons,implying that the superconductivity results mainly from the condensation of Cr 3d electrons.Pr3Cr10-xN11 represents a rare example of possible unconventional superconductivity emerging in a 3D system with strong electron correlations.Nevertheless,clarification of the specific pairing symmetry needs more investigation.Exploration of superconductivity in Cr-based compounds has attracted considerable interest because only a few Cr-based superconductors（CrAs, A2Cr3As3 and ACr3As3（A = K, Rb, Cs, Na）） have been discovered so far and they show an unconventional pairing mechanism. We report the discovery of bulk superconductivity at 5.25 K in chromium nitride in Pr3Cr10-xN11 with a cubic lattice structure. A relatively large upper critical field of Hc2（0） ～12.6 T is determined, which is larger than the estimated Pauli-paramagnetic pair-breaking magnetic field. The material has a large electronic specific-heat coefficient of 170 mJ K-2mol-1—about 10 times larger than that estimated by the electronic structure calculation,which suggests that correlations between 3d electrons are very strong in Pr3Cr10-xN11, and thus quantum fluctuations might be involved. Electronic structure calculations show that the density of states at the Fermi energy are contributed predominantly by Cr 3d electrons, implying that the superconductivity results mainly from the condensation of Cr 3d electrons. Pr3Cr10-xN11 represents a rare example of possible unconventional superconductivity emerging in a 3D system with strong electron correlations. Nevertheless,clarification of the specific pairing symmetry needs more investigation.

关 键 词：Cr-based SUPERCONDUCTORS nitrides STRONG ELECTRON CORRELATIONS UNCONVENTIONAL SUPERCONDUCTIVITY 

分 类 号：TB34[一般工业技术—材料科学与工程] O469[理学—凝聚态物理]