共查询到20条相似文献,搜索用时 15 毫秒
1.
FeSe基超导体作为铁基超导材料家族的重要组成部分,已经成为凝聚态物理研究的一个热点领域,对这类超导材料的探索和制备是研究其物理性质的基础.目前,对于FeSe基超导材料的探索主要集中于插层和外延单层FeSe薄膜.其中,通过插层方法获得的FeSe基超导材料具有独特的性质,且种类众多.本文介绍了近年来发现的一系列FeSe基高温超导材料,涵盖KxFe2Se2,AxNH3FeSe,LiOHFeSe和有机分子插层FeSe等,并针对各种材料,简述了其性质及影响. 相似文献
2.
3.
4.
铁基超导体呈现丰富的电子相图, 各种有序态相互交叠. 本文主要介绍利用核磁共振手段在空穴型和电子型掺杂的BaFe2As2以及LaFeAsO1-xFx这三种具有代表性的铁基超导体中探测到的反铁磁序与超导序的微观共存、量子临界点和量子临界行为. 实验发现, 无论在空穴型还是电子型掺杂的铁基超导体中, 反铁磁相变温度都随着掺杂被抑制, 并最终在某个掺杂量降到零温而形成量子临界点. 在反铁磁转变温度之上存在结构相变, 其转变温度也随着掺杂而降低. 核磁共振谱证实结构相变也形成一个量子临界点. 本文介绍核磁共振及输运测量揭示的这两种量子临界点附近存在的量子临界行为, 共存态下奇异的超导性质等. 相似文献
5.
6.
本文对比研究了超导材料磁测量中的SQUID法和Campbell法; 并用高压PIT法制备的超导材料MgB2作为测量样品,用两种方法,测量了超导样品的临界电流密度, 分别得到了样品的Jc-B关系曲线; SQUID法测量样品的外磁场可以达到6 T, 此时材料已经处于失超状态,此方法测得的结果是样品各个小区域结果的平均值, SQUID还可以用来进一步标度材料的钉扎力行为,研究材料磁特性. Campbell法测量只能测量到外磁场强度为0.4 T,外磁场的交流部分的频率可以达到800 Hz, 用这种测量方法得到的是整块样品的电流,由于测量计及材料内部微观结构缺陷等影响电流传输因素, 所测结果小于直流磁化法,但更切近材料实际电流,能用来深入研究材料内部结构差别对材料电性能的影响. 相似文献
7.
Our recent scanning tunneling microscopy (STM) studies of the NaFelxCoxAs phase diagram over a wide range of dopings and temperatures are reviewed. Similar to the high-Tc cuprates, the iron-based superconductors lie in close proximity to a magnetically ordered phase. Therefore, it is widely believed that magnetic interactions or fluctuations play an important role in triggering their Cooper pairings. Among the key issues regarding the electronic phase diagram are the properties of the parent spin density wave (SDW) phase and the superconducting (SC) phase, as well as the interplay between them. The NaFe l-xCoxAs is an ideal system for resolving these issues due to its rich electronic phases and the charge-neutral cleaved surface. In our recent work, we directly observed the SDW gap in the parent state, and it exhibits unconventional features that are incompatible with the simple Fermi surface nesting picture. The optimally doped sample has a single SC gap, but in the underdoped regime we directly viewed the microscopic coexistence of the SDW and SC orders, which compete with each other. In the overdoped regime we observed a novel pseudogap-like feature that coexists with supercon- ductivity in the ground state, persists well into the normal state, and shows great spatial variations. The rich electronic structures across the phase diagram of NaFel_xCoxAs revealed here shed important new light for defining microscopic models of the iron-based superconductors. In particular, we argue that both the itinerant electrons and local moments should be considered on an equal footing in a realistic model. 相似文献
8.
Kazuhisa Nishi 《Physics letters. A》2018,382(45):3293-3297
We design a new structure for a cuprate superconductor indicating the possibility of higher temperature superconductivity using our recently proposed composite fermions theory. It is constructed with modulation-doped superlattice structures, which are often used in the design of semiconductor superlattice devices. The superconductive critical temperature () was calculated in the superlattice structures of the superconductor in which the optimal doped CuO2 layer was sandwiched between two less-doped CuO2 layers. We find that if these structures could be realized in a cuprate superconductor such as Bi2Sr2Ca2Cu3O10 or HgBa2Ca2Cu3O9, the highest could attain the level of 300 K at atmospheric pressure. 相似文献
9.
Electronic phase diagram of NaFe_(1-x)Co_xAs investigated by scanning tunneling microscopy
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Our recent scanning tunneling microscopy (STM) studies of the NaFe1-xCoxAs phase diagram over a wide range of dopings and temperatures are reviewed. Similar to the high-T c cuprates, the iron-based superconductors lie in close proximity to a magnetically ordered phase. Therefore, it is widely believed that magnetic interactions or fluctuations play an important role in triggering their Cooper pairings. Among the key issues regarding the electronic phase diagram are the properties of the parent spin density wave (SDW) phase and the superconducting (SC) phase, as well as the interplay between them. The NaFe1-xCoxAs is an ideal system for resolving these issues due to its rich electronic phases and the charge-neutral cleaved surface. In our recent work, we directly observed the SDW gap in the parent state, and it exhibits unconventional features that are incompatible with the simple Fermi surface nesting picture. The optimally doped sample has a single SC gap, but in the underdoped regime we directly viewed the microscopic coexistence of the SDW and SC orders, which compete with each other. In the overdoped regime we observed a novel pseudogap-like feature that coexists with superconductivity in the ground state, persists well into the normal state, and shows great spatial variations. The rich electronic structures across the phase diagram of NaFe1-xCoxAs revealed here shed important new light for defining microscopic models of the iron-based superconductors. In particular, we argue that both the itinerant electrons and local moments should be considered on an equal footing in a realistic model. 相似文献
10.
用扫描隧道显微镜/谱仪仔细研究了铁基超导单晶FeSe0.5Te0.5样品的表面形貌和隧道谱, 测量到了清晰的表面原子形貌和在空间比较稳定的隧道谱结构.在样品中测量的隧道谱零能态密度比较高, 说明样品里面有比较强的非弹性准粒子散射. 在正能5 mV附近有个较大的背景鼓包, 这一背景在很高温度也未消失. 空间中Se和Te集中的位置会带来高能背景的变化, 超导能隙附近谱的形状大致相同. 较强的非弹性准粒子散射破坏了超导的准粒子散射, 因此没有在二维微分电导图中发现超导准粒子相干散射的特征亮斑. 相似文献
11.
铁基高温超导体自2008年发现以来,对其超导电性的研究一直是一个热门的课题.扫描隧道显微镜能够在原子尺度进行表面形貌和隧道谱测量,从微观角度研究电子态密度的信息,是研究超导的重要谱学手段.近年来,在铁基超导电性方面,扫描隧道显微镜实验已经积累了一些有价值的结果,本文进行了总结介绍.铁基超导体是多带多超导能隙的超导体,不同材料的费米面结构有很大的变化.扫描隧道显微镜证明,同时有电子和空穴费米面最佳掺杂的铁基样品超导能隙结构是无节点并带有能隙符号变化的s±波.而进一步的实验发现在没有空穴费米面的FeSe基超导体中也存在能隙符号的相反,对统一铁基超导体的配对对称性提供了重要实验证据.此外,扫描隧道显微镜在研究铁基超导体的电子向列相、浅能带特性、可能的拓扑特性方面,提供了重要的实验数据.本文对上述相关内容进行了总结,并做了相应分析和讨论. 相似文献
12.
Prabir K. Mukherjee 《Phase Transitions》2013,86(12):1211-1224
We present an improved analysis of the phase transitions in spin-triplet ferromagnetic superconductors within Ginzburg–Landau theory. We put special emphasis on the phase transitions from normal phase to the mixed phase of coexistence of ferromagnetism and unconventional superconductivity. We present a detailed analysis of the different phases that can occur and analyze the question under which conditions the phase transitions from normal phase to the mixed phase of coexistence of ferromagnetism and unconventional superconductivity are possible when compared to other phase transitions. The conditions for the phase transitions and the stability conditions are calculated. On the basis of this model, it is argued that the transition from normal phase to the mixed phase of coexistence is always of first order. It was observed from the theoretical calculations that the transition from the ferromagnetic phase to the coexistence phase can cross over from the first to the second order at the tricritical point. 相似文献
13.
14.
Electron-phonon coupling in cuprate and iron-based superconductors revealed by Raman scattering
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Electron-phonon coupling (EPC) in cuprate and iron-based superconducting systems, as revealed by Raman scat- tering, is briefly reviewed. We introduce how to extract the coupling information through phonon lineshape. Then we discuss the strength of EPC in different high-temperature superconductor (HTSC) systems and possible factors affecting the strength. A comparative study between Raman phonon theories and experiments allows us to gain insight into some crucial electronic properties, especially superconductivity. Finally, we summarize and compare EPC in the two existing HTSC systems, and discuss what role it may play in the HTSC. 相似文献
15.
单晶薄膜形态的高温超导材料对于相关基础科学研究和应用开发都极为重要.多带的铁基高温超导体往往呈现丰富的物理现象,并具有较高的超导临界参数.特别是近年发现的插层(Li,Fe)OHFeSe超导体,无论对高温超导机理还是应用研究而言,都日益受到重视,已成为铁基家族中重要的典型材料.但是,该化合物含有OH键,加热易分解.因此,现有的常规高温成膜技术均不适用于生长该薄膜材料.为解决这一生长难题,我们最近发明了基体辅助水热外延生长法,实现了超导薄膜制备技术上的突破.本文简要介绍用此软化学成膜技术首次成功制备出(Li,Fe)OHFeSe单晶薄膜.该薄膜材料具有优良的结晶质量和较高的超导临界参数,特别是其高的临界电流密度和上临界场对应用开发有实际价值.因此,(Li,Fe)OHFeSe超导单晶薄膜的成功合成,为机理研究和应用开发分别提供了重要的实验载体和备选材料.另外,该薄膜技术也有望应用于其他功能材料的探索与合成,尤其是对常规手段难以获取的材料更具重大价值. 相似文献
16.
Optical conductivity as a probe of a hidden Fermi-liquid behavior in BaFe_(1.904) Ni_(0.096) As_2
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We measured the infrared reflectivity of BaFe1.904Ni0.096As2 single crystal from room temperature down to 20 K.Two Drude terms and a Lorentz term well describe the real part of the optical conductivity σ1(ω). We fit the reciprocal of static optical conductivity 1/σ1(0) by the power law ρ(T)=ρ0+ATnwith n=1.6. The "broad" Drude component exhibits an incoherent background with a T-independent scattering rate 1/τb, while the other "narrow" one reveals a T-quadratic scattering rate 1/τn, indicating a hidden Fermi-liquid behavior in BaFe1.904Ni0.096As2 compound. 相似文献
17.
Majorana zero modes (MZMs) are Majorana-fermion-like quasiparticles existing in crystals or hybrid platforms with topologically non-trivial electronic structures. They obey non-Abelian braiding statistics and are considered promising to realize topological quantum computing. Discovery of MZM in the vortices of the iron-based superconductors (IBSs) has recently fueled the Majorana research in a way which not only removes the material barrier requiring construction of complicated hybrid artificial structures, but also enables observation of pure MZMs under higher temperatures. So far, MZMs have been observed in iron-based superconductors including FeTe0.55Se0.45, (Li0.84Fe0.16)OHFeSe, CaKFe4As4, and LiFeAs. In this topical review, we present an overview of the recent STM studies on the MZMs in IBSs. We start with the observation of MZMs in the vortices in FeTe0.55Se0.45 and discuss the pros and cons of FeTe0.55Se0.45 compared with other platforms. We then review the following up discovery of MZMs in vortices of CaKFe4As4, impurity-assisted vortices of LiFeAs, and quantum anomalous vortices in FeTe0.55Se0.45, illustrating the pathway of the developments of MZM research in IBSs. Finally, we give perspective on future experimental works in this field. 相似文献
18.
铁基超导体作为除铜氧化物超导体之外的第二类高温超导体,自从被发现以来其超导电性的成因就备受关注。早期有人针对同时具有空穴型费米口袋和电子型费米口袋的铁砷基超导体提出了S±配对模式,而且得到中子散射和隧道谱实验的初步支持。这一配对模型的基础是需要在布里渊区同时具有空穴型和电子型费米面。但是铁基超导体的费米面因材料而异,新发现的很多铁硒基超导体因缺乏空穴型费米面,对S±电子配对模型来说是一个挑战。文章综述了过去几年来作者在这方面取得的工作进展。运用高精度的扫描隧道显微镜,在不同铁基超导体系中,针对超导能隙结构,或超导序参量的性质进行了仔细研究。首先作者在铁砷基超导体NaFe1-xCoxAs和Ba1-xKxFe 2As2中利用无磁性杂质态测量和隧道谱测量,发现S±的明确证据。进一步,在只有电子型费米面的(Li1−xFex)OHFeSe超导材料中发现两个各向异性的超导能隙,利用准粒子相干散射实验第一次把这两个超导能隙对应到由电子型费米面套叠或杂化后形成的内外两套费米面上。通过非磁性杂质诱导产生的能隙内杂质态和新型电子驻波相位敏感实验的探测,证明该材料中超导能隙符号也发生反转。因此作者的系列工作统一了有和没有空穴型费米面的铁基超导体的能隙形式,支持排斥势是导致电子配对和超导电性产生的关键因素。 相似文献
19.
文章介绍了利用核磁共振法对铁基高温超导体的研究结果.笔者研究组断定铁基超导是自旋单态配对,并首先发现超导多能隙的存在.正常态的反铁磁自旋涨落在自旋空间是各向异性的,它与超导的关系,是人们关心的热点之一. 相似文献
20.
We report observation of possible superconducting transitions at 133 K, 117K and 105 K in Bi-Sr-Ca-Cu-O bulk samples which
attain zero resistance state above the liquid nitrogen temperature (Tc(0)) = 80K). The transition at 105 K is prominent and shows a significant drop in the sample resistance. X-ray data depict
characteristic superconducting peak at 20 = 5–6°. All the specimens show Meissner effect when cooled in liquid nitrogen. 相似文献