物理学院 School of Physics, Nanjing University

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Electronic Phase Control with an Electric Field

2017年11月03日

报告人:袁洪涛 教授
报告时间:11月07日 中午12:00
报告地点:唐楼B501
报告题目:Electronic Phase Control with an Electric Field

 
摘要:
Electric-field control of charge carrier density has attracted much attention since it is remarkably simple for modulating physical properties of condensed matters and for exploringnew functionalities with a transistor configuration. To realize novel field-effect modulated electronic phenomena in solids, a broad range of attainable carrier density is always required. However, so far, owing to the limitation of dielectric breakdown in most solid dielectrics, the maximum carrier density accumulated in conventional field-effect transistors(FETs) is quite low (<< 1013 cm-2) and thus seriously limits the tunability of electronic states of solids, for example, not sufficient enough to induce insulator-to-superconductor transition. While, recently a new type of transistor, known as electric-double-layer transistor (EDLT), with ionic liquids (ILs) as gate dielectrics have been proved to be able toeffectively attain a high carrier density up to levels of around 1015 cm-2 and to realize a large local electric field up to 50mV/cm at liquid/solid interfaces, which are attracting increasing interests because of their potential to greatly tune electronic states and even to create novel states of matter which are impossible or difficult to obtain in conventionalmethods. 
In this presentation, I will discuss the interfacial carrier accumulation within liquid gated EDLTs and their novel tunability of varied electronic phase transitions in oxides and chacogenides. Firstly, I will start with fundamentals of interface electrochemistry and charging mechanism in such fantastic liquid/solid EDL interfaces, for example the competation between electrochemistry charging and electrostatic charging, or the interfacial band alginment and band engineering confirmed with measuring working functions of different ILs by photoemmision spectroscopy (PES). Secondly, based on these investigations and by further taking great advantages of high carrier density at EDL interfaces (up to 1015 cm-2), I wil discuss some results on those electric-field-induced electronic transition including insulator metal transition, insulator-superconductor and carrier-mediated paramagnetism-ferromagnetism transition via modulating the interfacial carrier accumulation. Thridly, by taking the advantage of large local electric field (50MV/cm), spin-orbit interaction (SOI) and resulting spin splitting of energy band of 2D systems can be regulated with structure inversion asymmetry (SIA) originated from the interfacial band bending and large applied electric fields, and further be used for generating spin-polarized carriers in solids. I will discuss a field-effect-tuned SOI and some demonstration on energy spin splitting and sspin current generation, which is supposed to open a new direction of “spin manipulation with liquid” in “interface spintronics”.

 

 
报告人简介:
袁洪涛是在新型场效应器件、新奇异质界面及低温物理/电子输运研究领域中非常活跃的青年科学家,尤其在液栅场效应晶体管器件的设计开发,和低温电子输运方面做出了有特色性的科研成果。他的主要研究领域包括:利用在栅压条件下离子液体可在半导体表面形成电双层结构的原理,开发出了以离子液体作为介质材料的电双层场效应晶体管(Electric-Double-Layer Transistor)原型器件,在多种半导体材料上实现了场效应晶体管的高性能化、低功耗化和高导通化。并进一步把这种新型原型器件扩展到强关联材料和其他量子材料体系中,研究并观测到多种场效应诱导的奇异的界面物理现象, 比如场效应诱导的绝缘体-超导相变、顺磁-铁磁相变和Rashba/Zeeman自旋极化等。电双层电场调制技术目前吸引了众多国际国内同行的关注。
袁洪涛2007年于中国科学院物理研究所薛其坤课题组获博士学位。毕业后在日本东北大学岩佐羲宏研究组开展博士后研究工作。2010-2012随岩佐研究组转至东京大学应用物理系和东京大学量子相电子研究中心,先后担任东京大学助理研究员和助理教授。2012年初入职斯坦福大学Cui Yi和Harold Hwang研究组,先后担任助理研究员和Associate Staff Scientist,从事二维量子体系物理特性的场效应调制。2017年入选国家“青年千人计划”,任职南京大学现代工程与应用科学学院教授,博士生导师。截止2017年4月,已在高影响因子杂志上发表文章70余篇,其中包括Science,Nature子刊13篇(1篇Science,7篇Nature Nanotech., 1篇Nature Mater., 1篇Nature Physics,3篇Nature Commun.)以及3篇邀请综述,总引用4100余次,H-index为29。已授权国际国内专利18项。在包括APS/MRS/ECS/MMM年会在内的著名国际会议上做邀请报告二十余次。目前是 Nature Nanotech., Nature Commun.,Nano Letters,Advanced Materials,JACS等期刊特约审稿人。

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