锰氧化物相竞争的理论研究

锰氧化物属于典型的强关联电子材料,具有包括庞磁电阻、电荷/轨道有序、电子相分离、多铁性等奇特的物理特性。这些现象涉及一系列凝聚态物理学基本问题,是近年来研究者一直关注的热点和难点。并且这些奇异的电磁性质也为开发量子调控器件提供了基本素材。虽然近20年来对锰氧化物的研究取得了丰硕成果,全世界的研究者仍在为理解并应用其特性作着孜孜不倦的努力。本综述将主要从理论角度,重点关注钙钛矿结构锰氧化物中多种相竞争和调制。由于有着多种竞争相互作用和多重量子自由度,锰氧化物有着丰富的相,这些相物理特性迥异,而自由能却可能相当接近。因此,自发或人为调制导致的相竞争是锰氧化物研究的一个核心问题,也是整个强关联物理领域中一个很有意义的课题。本综述将以电致电阻、多铁性和异质结界面处电子重组这三个具体实例,介绍如何采用蒙特卡罗模拟等方法研究其中的相竞争和调制。

PHASE COMPETITIONS IN PEROVSKITE MANGANITES: A THEORETICAL REVIEW

Manganites are typical strongly correlated electronic materials.In manganites,there are various competing interactions.Novel properties,such as the colossal magnetoresistance(CMR),charge/orbital ordering,electronic phase separation,multiferroicity,emerge from these interactions between multi-degrees of freedom:charge,spin,orbital and lattice.All these phenomena,not only are attractive and challenging issues in condensed matter physics,but also provide great opportunities to design multifunctional quantum devices.This review mainly focuses on phase competitions in perovskite manganites from the theoretical viewpoint.In manganites,there are plenty phases with quite different properties,while their free energy can be quite close.Therefore,the phase competitions and how to modulate these competitions are the key issue of manganites,which are also important topics for other strongly correlated electronic materials.In this review,the microscopic model Hamiltonian for manganites,as well as several numerical techniques,such as the Monte Carlo simulation,will be introduced.Three particular cases:the colossal electroresistance,multiferroicity,and electronic reconstruction at heterostructures,will be studied to illustrate the phase competitions.