低维高温超导的启示:键收缩与电子双重极化  

Enlightening of the low-dimensional high-T;superconductivity:Bond contraction and electron dual polarization

作　　者：孙长庆 Chang-Qing Sun(School of Materials Science and Engineering,Jilin University,Changchun 130012,China;School of Electrical and Electronic Engineering,Nanyang Technological University,Singapore 639798,Singapore)

机构地区：[1]吉林大学材料科学与工程学院,长春130012 [2]School of Electrical and Electronic Engineering,Nanyang Technological University,Singapore 639798,Singapore

出　　处：《科学通报》2022年第2期113-117,共5页Chinese Science Bulletin

基　　金：国家自然科学基金(21875024)资助。

摘　　要：经典的Bardeen–Cooper–Schrieffer(BCS)理论[1~3]认为,费米面附近的电子通过电声耦合作用形成具有玻色子特征的库珀对,即玻色-爱因斯坦凝聚.库珀对在低温条件下相互协调,实现在晶格内无阻输运.虽然BCS理论能够很好地描述临界温度T_(C)低于30 K的金属或合金的常规超导行为,但是却不足以解释于1986年发现且持续发展的以铜氧掺杂为代表的新生代高温超导现象.在30多年的高温超导研究中,学者们坚持不懈地努力探讨新的物理机制[2,4],如电声作用、载流子的输运特性,以及铜氧面和载流子的本征起源和属性等.2021年5月,美国Science杂志携手上海交通大学发布了新的125个重要科学问题,其中包括高温超导的微观机理以及界面现象的微观测量.最近报道的准一维铜氧链的电子间超强吸引作用[5]、双层铜氧面具有与体相全同的超导行为[6],以及铁砷/镧铁氧界面超导现象[7],称为降维超导,尤其令人鼓舞.这些发现进一步激发了人们对探求电声作用机理及以铜氧面和铜氧链为代表的超导通道的物理本质和起因的研究兴趣.Electron-phonon interaction that couples the carriers for the Bose-Einstein condensation and the nature and configuration of the O-Cu chains and O-Cu planes that accommodate carriers are key issues to the cuprite high-T;superconductivity discovered in 1986. However, the new kind of high-T;superconductivity is beyond the description of the conventional Bardeen–Cooper–Schrieffer(BCS) theory. Here we address these two issues based on the bond order-length-strength correlation and nonbonding electron polarization(BOLS-NEP) notion for the effect of atomic undercoordination and the hydrogen bond(O:H-O equivalent of O:Cu-O) cooperativity and polarizability(HBCP) premise for water ice with involvement of electron lone pairs “:” interactions. First, a Cu;:O:Cu;dipolar chain is formed by connecting a series of tetrahedrons made of two Cu;ions and two Cu;dipoles surrounding the center O;. The O-Cu(110) plane includes three sublayers. The first one is made of alternative rows of Cu0 vacancies and the Cu;:O:Cu;dipolar chain with dipoles pointing out the surface;the second sublayer is formed by O;whose lone pairs polarize the dipoles and squeeze out the missing rows of Cu atoms, and the third sublayer is made of Cu;. However, the O-Cu(001) plane shows a different manner of the sublayers. The first sublayer is made of Cu;, Cu;, and Cu;, and the third sublayer of Cu;and Cu. The O;bonds to the Cu;and polarizes the Cu to form the oppositely-coupled dipoles on the Cu(001) surface. The O-Cu bonding proceeds in four discrete stages: O;bonds to one Cu to form the Cu;-2O;and then each O–bonds to its neighboring Cu in the second layer to form the twin tetrahedron with the production of the lone pairs. The introduction of O to Cu host creates valence density features of the O-Cu bonding, lone pair nonbonding, the dipolar antibonding above E;, and electron holes. Second, atomic undercoordination of the O-Cu chains and the O-Cu planes shortens and stiffens the local O-Cu bond and lengthens and weakens the O:Cu;nonbonding interact

关 键 词：上海交通大学 高温超导 铜氧面 超导现象 界面现象 物理本质 BCS理论 玻色子 

分 类 号：O469[理学—凝聚态物理]