掺杂维度和浓度调控的δ掺杂的La:SrTiO_(3)超晶格结构金属-绝缘体转变  

Tuning metal-insulator transition in δ-doped La:SrTiO_(3)superlattice by varying doping dimensionality and concentration

作　　者：李云 鲁文建 Li Yun;Lu Wen-Jian(School of Physics and Electronic Engineering,Hanshan Normal University,Chaozhou 521041,China;Institute of Solid State Physics,HFIPS,Chinese Academy of Sciences,Hefei 230031,China)

机构地区：[1]韩山师范学院物理与电子工程学院,潮州521041 [2]中国科学院合肥物质科学研究院固体物理研究所,合肥230031

出　　处：《物理学报》2021年第22期270-274,共5页Acta Physica Sinica

基　　金：教育部留学回国人员科研启动基金(批准号:[2015]-1098)资助的课题.

摘　　要：利用密度泛函理论计算,本文系统研究了δ掺杂的La:SrTiO_(3)超晶格结构的电子性质随掺杂维度和掺杂浓度改变而变化的规律性.该结构通过在SrTiO_(3)等间距的单元层中掺入一定浓度的La来实现.在25%La掺杂浓度下,随着相邻掺杂层间距从1个单层增加到δ个单层,掺杂维度从三维过渡到二维,超晶格从金属性变到绝缘体性,并在带隙中产生局域态,且该局域态呈现出电荷序、自旋序和轨道序.这种金属-绝缘体转变是由于二维电子体系呈现出更强的关联性造成的.而随着二维掺杂浓度提高到50%,关联性降低,体系变成金属性.Electronic properties in δ-doped La:SrTiO_(3) superlattices varying with the doping dimensionality and concentration are systematically studied through using first-principles calculation.The superlattices consist of periodically repeated La-doped single SrTiO_(3) layers in SrTiO_(3) film,and the doping dimensionality can be tuned by varying the space of the neighboring doped layers.At 25%doping concentration,the spacing between SrTiO_(3) layers increases from 1 unit-cell layer to 5 unit-cell layers,i.e.the doping dimensionality changes three dimensions to two dimensions,the superlattice charater changes from metallic character into insulating character,and the charge sequence,spin sequence and orbital sequence are present in a localized state.This metal-insulator transition is ascribed to the stronger correlation effect in the two-dimensional electron system.With the two-dimensional doping concentration increasing to 50%,the correlation effect becomes weak and the system becomes metallic.

关 键 词：二维掺杂 强关联 金属-绝缘体转变 

分 类 号：O469[理学—凝聚态物理] TB30[理学—电子物理学]