极性界面Hubbard-Holstein模型中的电子相和相分离
Electronic Phases and Phase Separation in the Hubbard-Holstein Model of a Polar Interface
摘要：
从平均场解的Hubbard-Holstein模型，我们表明，丰富的各种不同的电子相可以导致在两个极性材料之间的界面，如LaAlO $_3$ /SrTiO $_3$。根据各种竞争相互作用的强度，即，电子动能、电子-声子相互作用、库仑能和电子屏蔽强度，电子可以（i）被强烈地限制在界面上，形成2D金属相或绝缘相，（ii）更深地扩散到块体中，形成3D相，或（iii）变得局限在单个位点上，形成Jahn-Teller极化子相。在极化相，库仑相互作用可以导致未成对电子，从而导致磁近藤中心。在适当的条件下，电子相分离也可能发生，导致在界面处的金属和绝缘区域的共存。
英文摘要：
From a mean-field solution of the Hubbard-Holstein model, we show that a rich variety of different electronic phases can result at the interface between two polar materials such as LaAlO$_3$/SrTiO$_3$. Depending on the strengths of the various competing interactions, viz., the electronic kinetic energy, electron-phonon interaction, Coulomb energy, and electronic screening strength, the electrons could (i) either be strongly confined to the interface forming a 2D metallic or an insulating phase, (ii) spread deeper into the bulk making a 3D phase, or (iii) become localized at individual sites forming a Jahn-Teller polaronic phase. In the polaronic phase, the Coulomb interaction could lead to unpaired electrons resulting in magnetic Kondo centers. Under appropriate conditions, electronic phase separation may also occur resulting in the coexistence of metallic and insulating regions at the interface.
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