强自旋轨道耦合化合物Sr_(2-x)La_xIrO_4的掺杂和拉曼谱学  

Doping and Raman scattering of strong spin-orbit-coupling compound Sr_(2-x)La_xIrO_4

作　　者：刘胜利[1,2] 厉建峥 程杰[1] 王海云[1] 李永涛[1] 张红光[1] 李兴鳌[4] 

机构地区：[1]南京邮电大学先进功能陶瓷研究中心,南京210003 [2]南京大学(苏州)高新技术研究院,苏州215123 [3]南京邮电大学电子科学与工程学院,南京210003 [4]南京邮电大学材料科学与工程学院,南京210003

出　　处：《物理学报》2015年第20期335-342,共8页Acta Physica Sinica

基　　金：江苏省高校自然科学基金(批准号:13KJB140012);江苏省自然科学基金(批准号:BK20130376;BK20130855);国家自然科学基金(批准号:51172110;11405089);苏州市科技局纳米技术专项基金(批准号:ZXG201444);江苏省"六大人才高峰"高层次人才基金(批准号:2014-XCL-015)资助的课题~~

摘　　要：利用固相反应法成功制备了Sr_(2-x)La_xIrO_4系列掺杂样品,并详细研究了样品晶体结构随掺杂的演变.拉曼散射峰向高频移动和X射线衍射谱的结构精修数据发现随着掺杂量的增加,c轴晶格常数减小,顶角Ir—O1键键长随之减小,表明掺杂导致晶格收缩,而且IrO_6八面体畸变程度减弱.变温拉曼散射谱显示随着温度降低也出现蓝移现象,且与顶角氧相关的拉曼振动模式的蓝移在110 K附近出现明显跳变,表明在该温度附近出现了结构变化和磁性质转变.Novel unconventional physical phenomena,such as metal-insulator transition,high temperature superconductivity,colossal magneto-resistance and quantum criticality,are usually found in transition metal oxides（TMOs） with layered perovskite structures.Great success has been achieved in 3d TMOs,in which the localized 3d states yield strongly correlated narrow bands with a large on-site Coulomb repulsion U and a small band width W.Anomalous insulating behaviors are reported in the 5d TMOs,such as Sr_2IrO_4 system,which is surprising since the 5d TMOs are usually considered as weakly correlated wide band systems with largely reduced on-site Coulomb repulsion U due to delocalized5 d states.The crystal structure of Sr_2IrO_4 consists of two-dimensional（2D） IrO_2 layers,similar to the parent compound La_2CuO_4 of the cuprates.Theoretically,a variational Monte Carlo study of Sr_2IO_4 suggests that d-wave like superconductivity may appear but only within a narrow region of electron doping.In contrast,an s±~＊-wave phase is established for hole doping deduced from functional renormalization group,and triggered by spin fluctuations within and across the two conduction bands.Moreover,triplet p-wave pairing state with relatively high transition temperature emerges on the hole-doped side when the Hund＇s coupling is comparable to spin-orbit coupling.Several experiments are tried to search for the predicted unconventional superconductivity due to both electron-and hole-doping.However,to the best of our knowledge,it has not been found yet in the carrier-doped Sr_2IrO_4 system.Hence,more detailed studies are needed to explore the potential superconductivity.A series of La doped Sr_（2-x）La_xIrO_4 samples is synthesized based on solid state reaction method.The evolution of the crystal structure is studied by the X-ray diffraction,scanning electron microscopy,together with the Raman spectrum.It is found that the crystal constant of the c-axis decreases with increasing doping level as well as the apical Ir—01bond length

关 键 词：自旋轨道耦合 拉曼光谱 晶体结构 

分 类 号：O469[理学—凝聚态物理] O483[理学—电子物理学]