Enhanced superconductivity in atomically thin TaS2
Efrén Navarro-Moratalla, Joshua O. Island, Samuel Mañas-Valero, Elena Pinilla-Cienfuegos, Andres Castellanos-Gomez, Jorge Quereda, Gabino Rubio-Bollinger, Luca … 展开作者
Efrén Navarro-Moratalla, Joshua O. Island, Samuel Mañas-Valero, Elena Pinilla-Cienfuegos, Andres Castellanos-Gomez, Jorge Quereda, Gabino Rubio-Bollinger, Luca Chirolli, Jose Angel Silva-Guillén, Nicolás Agraït, Gary A. Steele, Francisco Guinea, Herre S. J. van der Zant, Eugenio Coronado
The ability to exfoliate layered materials down to the single layer limit has opened the opportunity to understand how a gradual reduction in dimensionality affects the properties of bulk materials. Here we use this top-down approach to address the problem of superconductivity in the two-dimensional limit. The transport properties of electronic devices based on 2H tantalum disulfide flakes of different thicknesses are presented. We observe that superconductivity persists down to the thinnest layer investigated (3.5 nm), and interestingly, we find a pronounced enhancement in the critical temperature from 0.5 K to 2.2 K as the layers are thinned down. In addition, we propose a tight-binding model, which allows us to attribute this phenomenon to an enhancement of the effective electron-phonon coupling constant. This work provides evidence that reducing dimensionality can strengthen superconductivity as opposed to the weakening effect that has been reported in other 2D materials so far.
Influence of nano-hole defects and their geometric arrangements on the superfluid density in atomically thin single crystals of indium superconductor
以Si（111）衬底上的铟（Indium on Si）为原子级薄超导体平台，通过系统地控制纳米孔洞缺陷（纳米尺寸空洞）的密度，揭示了缺陷密度和缺陷几何排列对宏观和微观尺度上超导性的影响.当纳米孔缺陷均匀地分散在原子层中时，超流密度作为缺陷密度的函数（从表面积的0.7%至5%）单调地减小，在转变温度Tc中具有微小的变化，微观和宏观上测量。随着缺陷密度从5%到6%的略微增加，这些点缺陷被组织成包含单个二维补丁的缺陷链。这种新的缺陷几何排列对超导性产生了巨大的影响，导致宏观超流密度的完全消失和微观超导能隙的崩塌。这项研究为理解局部缺陷及其几何排列如何影响二维极限中的超导性提供了新的思路。
Sign reversing Hall effect in atomically thin high temperature superconductors
我们制作了范德华异质结器件，使用几个单位晶胞厚度的Bi $_2$ Sr $_2$ CaCu $_2$ O $_{8+δ}$的磁输运测量。原子级薄样品的超导转变温度和载流子密度可以保持接近大块样品。在大块样品中，霍尔电导率的符号被发现是相反的正常状态附近的转变温度，但随着样品的厚度减小的温度-磁场相图中的霍尔符号反转的区域急剧扩大。基于涡核中的过剩电荷密度和超导涨落的霍尔符号反转的定量分析表明，在二维极限下，原子级薄样品中存在重整化的超导能隙。
Enhanced superconductivity in atomically thin noble metals: From quantum confinement to interface-induced Lifshitz transition
School of Physical Science and Technology, Inner Mongolia University（内蒙古大学物理科学与技术学院）；Key Laboratory of Semiconductor Photovoltaic Technology and Energy Materials at Universities of Inner Mongolia Autonomous Region, Inner Mongolia University（内蒙古自治区高校半导体光伏技术与能源材料重点实验室）；Research Center for Quantum Physics and Technologies, Inner Mongolia University（内蒙古大学量子物理与技术研究中心）；Inner Mongolia Key Laboratory of Microscale Physics and Atomic Manufacturing, Inner Mongolia University（内蒙古微尺度物理与原子制造重点实验室）
Atomically-flat, chemically-stable, superconducting epitaxial thin film of iron-based superconductor, cobalt-doped BaFe$_2$As$_2$
最近报道了诸如Co掺杂的SrFe $_2$ As $_2$（SrFe $_2$ As $_2$：Co）的Fe基超导体的外延生长，但是由于它们具有粗糙的表面并且通过与环境大气中的水蒸气的反应而分解，因此对于器件应用而言仍然具有不足的性能。本文报道了在700 ℃下生长的Co掺杂BaFe $_2$ As $_2$外延膜的超导转变起始温度为20 K。该转变比在SrFe $_2$ As $_2$：Co膜上观察到的转变更尖锐，这将源于它们改进的结晶度。这些薄膜还具有原子级平坦的表面，具有台阶和露台结构，并表现出抗水蒸气暴露的化学稳定性。
