摘要
本文报道了非中心对称化合物家族La_(4)TX(T=Ru,Rh,Ir;X=Al In)中的超导电性.该系列超导体具有立方晶体结构,空间群为F 43m La_(4)RuAl,La_(4)RhAl,La_(4)IrAl,La_(4)RuIn和La_(4)IrIn的超导转变温度在0.61–3.35 K之间,而La_(4)RuIn尚未被成功制备.La_(4)RuAl和La_(4)RhAl的低温比热可由无超导能隙节点的s波超导描述,而自旋-轨道耦合强度较大的La_(4)IrAl则可能存在能隙节点.这些超导体的上临界磁场都可由Werthamer-Helfand-Hohenberg模型描述,且上临界场Hc2(0)远低于泡利极限,说明轨道效应在库伯对拆对机制中占据主导.密度泛函理论计算表明,对于该超导家族的不同化合物,其反对称自旋-轨道耦合导致的能带劈裂存在明显区别,有助于进一步探究超导配对态与反对称自旋-轨道耦合强度之间的联系.
We report the discovery of superconductivity in a series of noncentrosymmetric compounds La_(4)TX(T = Ru,Rh, Ir;X = Al, In), which have a cubic crystal structure with the space group F 43m. La_(4)RuAl, La_(4)RhAl, La_(4)IrAl, La_(4)RuIn and La_(4)IrIn exhibit bulk superconducting transitions with critical temperatures(Tc) of 0.61–3.35 K, while La_(4)RhIn was not successfully synthesized. The specific heats of La_(4)RuAl and La_(4)RhAl are best accounted for by an s-wave model with a fully open superconducting gap, while a nodal gap cannot be excluded for La_(4)IrAl, which has stronger antisymmetric spinorbit coupling(ASOC). In all cases, the upper critical fields are well described by the Werthamer-Helfand-Hohenberg model,and the values are well below the Pauli limit, indicating that orbital limiting is the dominant pair-breaking mechanism.Density functional theory(DFT) calculations reveal that the degree of band splitting by the ASOC shows considerable variation between the different compounds. This indicates that the strength of the ASOC is highly tunable across this series of superconductors, suggesting that they are good candidates for examining the relationship between ASOC and superconducting properties in noncentrosymmetric superconductors.
作者
苏杭
杜锋
罗帅帅
聂智勇
李蕊
谢武
沈斌
王云枫
王安
Toshiro Takabatake
曹超
Michael Smidman
袁辉球
Hang Su;Feng Du;Shuaishuai Luo;Zhiyong Nie;Rui Li;Wu Xie;Bin Shen;Yunfeng Wang;An Wang;Toshiro Takabatake;Chao Cao;Michael Smidman;Huiqiu Yuan(Center for Correlated Matter and School of Physics,Zhejiang University,Hangzhou 310058,China;Zhejiang Province Key Laboratory of Quantum Technology and Device,School of Physics,Zhejiang University,Hangzhou 310058,China;Department of Quantum Matter,Graduate School of Advanced Science and Engineering,Hiroshima University,Higashi-Hiroshima 739-8530,Japan;Condensed Matter Group,Department of Physics,Hangzhou Normal University,Hangzhou 311121,China;State Key Laboratory of Silicon Materials,Zhejiang University,Hangzhou 310058,China;Collaborative Innovation Center of Advanced Microstructures,Nanjing University,Nanjing 210093,China)
基金
supported by the Key R&D Program of Zhejiang Province,China(2021C01002)
the National Natural Science Foundation of China(11874320,12034017,11874137,and 11974306)
the National Key R&D Program of China(2017YFA0303100)
Zhejiang Provincial Natural Science Foundation of China(R22A0410240).
