Sr掺杂对La_(1-x)Sr_xMnO_3/LaAlO_3/SrTiO_3界面电子结构的影响  

Effect of Sr doping on electronic structure of La_(1-x)Sr_xMnO_3/LaAlO_3/SrTiO_3 heterointerface

作　　者：阮璐风 王磊 孙得彦 Ruan Lu-Feng Wang Lei Sun De-Yan(Department of Physics, School of Physics and Material Science, East China Normal University, Shanghai 200241, China Received 27 April 2017, revised manuscript received 10 June 2017)

机构地区：[1]华东师范大学物理与材料科学学院物理学系,上海200241

出　　处：《物理学报》2017年第18期210-217,共8页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11174079);国家重点基础研究发展计划(批准号:2012CB921401)资助的课题~~

摘　　要：采用基于密度泛函理论的第一性原理计算方法,系统地研究了La_(1-x)Sr_xMnO_3层中Sr的掺杂方式和掺杂量对4La_(1-x)Sr_xMnO_3/3LaAlO_3/4SrTiO_3(LSMO/LAO/STO)异质结构原子和电子结构的影响.结果表明:对于相同的Sr掺杂量,掺杂方式的差异对体系电子结构的影响微弱,不会导致体系发生金属-绝缘体转变;掺杂量的不同对体系电子结构有着显著的影响,当Sr的掺杂量较少时,LAO/STO界面处存在着准二维电子气,当Sr的掺杂量高于1/3时,LAO/STO界面处准二维电子气消失.我们相信,Sr的引入以及通过Sr掺杂量的改变可以对LSMO覆盖层极化进行调控,这也是导致体系LAO/STO界面处金属-绝缘体转变的可能原因,进一步为极化灾变机制导致的界面处电子重构提供了证据.In the past decades, the interface between two oxides LaAlO_3（LAO） and SrTiO_3（STO） has attracted much attention since a quasi-two-dimensional electron gas（q2DEG） at the interface was observed. It is generally believed that polar discontinuity at polar/non-polar oxide interface is responsible for the emergence of q2DEG at the interface. Recently,how to modulate the q2DEG at the interface is becoming a new research focus. Capping other oxide thin layer on LAO layer is one of alternative approaches to controlling the generation of q2DEG at interface. However the mechanism or origin for tuning q2DEG at capped LAO/STO interface has not yet completely understood. Using the first-principles calculations within the density functional theory, the electronic properties of La_（1-x）Sr_xMnO_3-capped LaAlO_3/SrTiO_3 heterointerfaces with different doping concentrations of Sr atoms are investigated. The system is composed of four layers of La_（1-x）Sr_xMnO_3（LSMO）, three layers of LAO and four layers of STO, denoted as 4LSMO/3LAO/4STO. The interface is normal to the [001] direction of cubic phase, namely（La_（1-x）Sr_xO） layer and（MnO_2） layer appear alternately at LSMO,and（LaO） layer and（AlO_2） layer appear alternately at LAO. In the absence of LSMO layers, q2DEG does not appear at the LAO/STO interface. It is found that the electronic structure of 4LSMO/3LAO/4STO can be tuned significantly by capping LSMO layers. For concentration of doped Sr atoms less than 1/3, a q2DEG at LAO/STO interface is observed.In this case, a strong polarization existing in LSMO, together with the polarization in LAO, forces the electrons to be redistributed, thus inducing the q2DEG at LAO/STO interface. With the increase of the concentration of Sr atoms,the polarization in LSMO becomes weaker and weaker. When the concentration is higher than 1/3, the polaried electric field fails to make the electrons redistributed, thus the q2DEG disappears from interface.Another interesting feature of the present work rel

关 键 词：第一性原理计算 氧化物异质结构 掺杂 准二维电子气 

分 类 号：O469[理学—凝聚态物理]