Studies on the superconductivity for the “111” type iron arsenide superconductor

The “111” type Li _x FeAs (x ranges from 0.8 to 1.2) with Cu₂Sb type tetragonal structure was synthesized with T _c 18 K. The isostructure NaFeAs was further studied, which shows superconductivity with T _c up to 26 K. The effect of pressure on superconductivity was investigated.     

金属氢:千呼万唤始出来 犹抱琵琶半遮面

<正>多年来,许多物理学家宣称他们通过加压将氢气转变为金属态,但是却没有人能给出令人信服的证据。现在法国研究人员认为他们已经找到了确凿的证据证实了氢的金属化,他们构建了新装置用来给极小样品加压,并且观察到了金属氢的红外吸收现象。然而,还是有研究者仍不信服这一结果,认为只有电学测量才能提供最充分的证据。人们对于足够高的压力能把氢     

“111”铁基超导体系的发现及压力效应研究

2008年发现的铁基超导体引发了全球超导研究的热潮。在本研究小组发现的铁基“111”体系的基础上,重点介绍“111”体系铁基超导体的压力效应,包括:“111”体系的3个组元LiFeAs、LiFeP、NaFeAs的超导转变随压力的演化;运用压力调控,获得“111”体系的最高超导转变温度;结合同步辐射技术,发现压力调控的“111”型铁基超导体的等结构演化以及对超导起关键作用的As-Fe-As键长和键角与超导转变温度的关联。     

面向应用的新一代稀磁半导体研究进展

稀磁半导体具有能同时调控电荷与自旋的特性,是破解摩尔定律难题的候选材料之一.我们团队率先提出了稀磁半导体中自旋和电荷掺杂分离的机制,探索并研制了新一代稀磁半导体材料,为突破经典稀磁半导体材料的制备瓶颈提供了有效解决方案.以(Ba,K)(Zn,Mn)₂As₂等为代表的新一代稀磁半导体,通过等价态的Mn掺杂引入自旋、异价态的非磁性离子掺杂引入电荷,成功实现了230 K的居里温度,刷新了可控型稀磁半导体的居里温度记录.本文将重点介绍几种代表性的新一代稀磁半导体的设计与研制、新一代稀磁半导体的综合物性表征、大尺寸单晶生长以及基于单晶的安德烈夫异质结研制.我们团队通过新一代稀磁半导体的新材料设计研制、综合物性研究、简单原型器件构建的“全链条”模式研究,开拓了自旋电荷分别掺杂的稀磁半导体材料研究领域,充分展现了自旋和电荷掺杂分离的新一代稀磁半导体材料潜在应用前景.     

Synthesis,structure, and properties of Ba9Co3Se(15) with one-dimensional spin chains

A new compound with one-dimensional spin chains, Ba9Co3Se(15), was synthesized under high pressure and high temperature conditions and systematically characterized via structural, transport and magnetic measurements. Ba9Co3Se(15) crystallizes in a hexagonal structure with the space group P-6c2(No. 188) and lattice constants of a = b = 9.6765 ? and c = 18.9562 ?. The structure consists of trimeric face-sharing octahedral CoSe6 chains, which are arranged in a triangular lattice in the ab-plane and separated by Ba atoms. The distance of the nearest neighbor of CoSe6 chains is very large, given by the lattice constant a = 9.6765 ?. The Weiss temperature Tθ associated with the intra-chain coupling strength is about -346 K. However, no long-range magnetic order but a spin glass transition at ~ 3 K has been observed. Our results indicate that the spin glass behavior in Ba9Co3Se(15) mainly arises from the magnetic frustration due to the geometrically frustrated triangular lattice.     

电荷自旋注入机制分离的新型稀磁半导体

兼具电荷属性和自旋特性的稀磁半导体将有可能突破Moore定律的瓶颈。文章介绍了作者实验室近年来发现和研究的电荷自旋注入机制分离的新型稀磁半导体,目前这类新型稀磁半导体的铁磁转变温度可以与相比拟,并有望进一步实现室温铁磁。     

Structural stability at high pressure,electronic, and magnetic properties of BaFZnAs:A new candidate of host material of diluted magnetic semiconductors

The layered semiconductor BaFZnAs with the tetragonal ZrCuSiAs-type structure has been successfully synthesized.Both the in-situ high-pressure synchrotron x-ray diffraction and the high-pressure Raman scattering measurements demonstrate that the structure of BaFZnAs is stable under pressure up to 17.5 GPa at room temperature. The resistivity and the magnetic susceptibility data show that BaFZnAs is a non-magnetic semiconductor. BaFZnAs is recommended as a candidate of the host material of diluted magnetic semiconductor.     

自旋和电荷分别掺杂的新一类稀磁半导体研究进展

稀磁半导体兼具半导体材料和磁性材料的双重特性,是破解摩尔定律难题的方案之一.我们团队通过提出自旋和电荷分别掺杂的机制,研制发现了一类新型稀磁半导体材料,为突破经典稀磁半导体材料自旋和电荷一体掺杂引起的材料制备瓶颈提供了有效解决方案.(Ba,K)(Zn,Mn)_2As_2(BZA)等新型稀磁半导体通过等价掺杂磁性离子引入自旋、异价非磁性离子掺杂引入电荷,实现了230 K的居里温度,刷新了可控型稀磁半导体的居里温度记录.本文重点介绍1)几种代表性的自旋和电荷掺杂机制分离的新型稀磁半导体的发现与研制; 2)新型稀磁半导体的μ子自旋弛豫与高压物性结构的调控; 3)大尺寸单晶生长、基于单晶的安德烈夫异质结研制以及自旋极化率的测量.通过新材料设计研制、综合物性研究、简单原型器件构建的"全链条"模式研究,开拓了自旋电荷分别掺杂的稀磁半导体材料研究领域,展现了这类新型稀磁半导体材料潜在的光明前景.