最近提出的多带超导性占主导地位的两个间隙的功能,挑战早期接受的节$d$波配对在第一个非常规超导体CeCu $_{2}$ Si $_{2}$。本文通过第一性原理计算得到了CeCu $_{2}$ Si $_{2}$的多带费米面拓扑结构,并在一个包含详细能带结构的有效双杂化能带模型下研究了该问题.在T-矩阵近似下,我们的计算表明,不同的配对候选人可以产生定性不同的特征,其特征在于杂质诱导的束缚态。除无节$s^{\pm}$波外,环节$s$波和$d$波对都能产生带隙内杂质束缚态.特别地,$d_{x^2-y^2}$波和环结$s$波的能隙内态是可区分的,并且分别位于费米能附近或远离费米能。这些功能可以很容易地通过高分辨率扫描隧道显微镜/光谱学验证,并提供了一个明确的理由正在进行的辩论有关的超导能隙对称性CeCu $_{2}$ Si $_{2}$在环境压力下。
英文摘要:
Multiband superconductivity with dominant two-gap features are recently proposed to challenge the earlier accepted nodal $d$-wave pairing in the first unconventional superconductor CeCu$_{2}$Si$_{2}$. Here we obtain multiband Fermi-surface topology of CeCu$_{2}$Si$_{2}$ via first-principles calculations, and study the problem within an effective two hybridization band model including detailed band-structure. Within T-matrix approximation, our calculations reveal that different pairing candidates could yield qualitatively distinct features characterised by impurity-induced bound states. Except for the nodeless $s^{\pm}$-wave, both loop-nodal $s$-wave and $d$-wave pairings can give rise to intra-gap impurity bound states. In particular, the intra-gap states for the $d_{x^2-y^2}$-wave and loop-nodal $s$-wave are distinguishable and locate either near or far away from the Fermi energy, respectively. These features can be readily verified by high-resolution scanning tunneling microscopy/spectroscopy and provide an unambiguous justification for the ongoing debate about the superconducting gap symmetry of CeCu$_{2}$Si$_{2}$ at ambient pressure.
Hidden Crossover Phenomena in Strongly Pauli Limited Multiband Superconductors ---Application to CeCu$_2$Si$_2$
基于最近对重费米子材料CeCu $_2$ Si $_2$和UBe $_{13}$的实验研究,我们建立了一个框架来描述具有强泡利顺磁效应(PPE)的多带超导体的一般性质.与单带情况相比,即使在强PPE情况下,上临界场$H_{\rm c2}$仍能保持二级跃迁。预期的一阶跃迁隐藏在$H_{\rm c2}$内部,并由于多频带的相互作用而成为交叉。本文基于微观Eilenberger理论的完全自洽解,解释了最近在CeCu $_2$ Si $_2$上的STM实验中观察到的与交叉和“空”涡核态有关的几种神秘异常现象。
Revealing sign-reversal $s^{+-}$-wave pairing by quasiparticle interference in the heavy-fermion superconductor CeCu$_2$Si$_2$
最近在超导体CeCu $_2$ Si $_2$中观察到的两个无结能隙引起了人们对它的确切能隙结构是反号($s^{+-}$)还是保号($s^{++}$)配对的激烈争论。在这里,我们调查的准粒子干涉(QPI)使用现实的费米面拓扑结构的弱和强带间杂质散射。我们的QPI和积分反对称局域态密度的计算揭示了$s^{+-}$和$s^{++}$配对状态之间的定性区别,其中包括间隙内杂质共振和两个间隙能量之间的显着的能量依赖性差异。我们的预测提供了一个指导相敏QPI测量发现果断的重费米子超导体CeCu $_2$ Si $_2$真正的配对对称性。
Higgs-mode resonance in third harmonic generation in NbN superconductors: multiband electron-phonon coupling, impurity scattering, and polarization-angle dependence
Multiorbital singlet pairing and $d+d$ superconductivity
最近在多带铁基和重费米子超导体的实验已经挑战了简单$s$-和$d$-波自旋单重态之间的长期持有的二分法。在这里,我们提出了几个时间反演不变的不可约配对,超越了标准的单态函数,通过在带/轨道空间中的矩阵结构,并阐明其在多带系统的自然性。本文研究了Fe硫系超导体的$sτ_{3}$多轨道超导态。这种状态对应于$d+d$带内和带间配对,与更熟悉的$d +\text{i}d$状态形成对比,其方式类似于\enhe超流体的B-三联体配对阶段与其A-阶段对应物的不同。此外,我们构建了一个类似的$sτ_{3}$配对的重费米子超导体CeCu $_{2}$ Si $_{2}$,使用的自由度,将自旋轨道耦合。我们的结果导致的命题,$d$波超导体在相关的多带系统将一般有一个完全带隙的费米面时,他们在足够低的能量检查。
Distinguishing impurity-induced bound states from Majorana-like zero-energy peaks in strained CsCa2Fe4As4F2 by scanning tunneling microscopy
Hefei National Research Center for Physical Sciences at the Microscale and Department of Physics, University of Science and Technology of China(中国科学技术大学物理系和微尺度物质科学国家研究中心);School of Physics, Zhejiang University(浙江大学物理学院);New Cornerstone Science Laboratory, Hefei National Laboratory(合肥国家实验室新 cornerstone 科学实验室)
Nonmonotonic Evolution of the Superconducting Transition Temperature and Robust Multigap Extended s-wave + s-wave Pairing in Zn-Substituted FeSe Single Crystals
Department of Applied Physics, Anhui Medical University(安徽医科大学应用物理系);Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China(中国科学技术大学微尺度物质科学国家研究中心);Materials Sciences Division, Lawrence Berkeley National Lab(劳伦斯伯克利国家实验室材料科学部);Department of Materials Science and Engineering, University of California, Berkeley(加州大学伯克利分校材料科学与工程系);Engineering Technology Research Center of Magnetic Materials, School of Physics & Materials Science, Anhui University(安徽大学物理与材料科学学院磁性材料工程技术研究中心);Anhui Key Laboratory of Low-Energy Quantum Materials and Devices, High Magnetic Field Laboratory, Chinese Academy of Sciences(中国科学院合肥物质科学研究院强磁场科学中心安徽省低能量子材料与器件重点实验室);Materials Characterization and Preparation Facility, The Hong Kong University of Science and Technology (Guangzhou)(香港科技大学(广州)材料表征与制备平台);Advanced Materials Thrust, Function Hub, The Hong Kong University of Science and Technology (Guangzhou)(香港科技大学(广州)功能枢纽先进材料领域);Institute of Applied Physics and Materials Engineering, University of Macau(澳门大学应用物理学与材料工程研究所);Department of Chemistry, University of Science and Technology of China(中国科学技术大学化学系)
Direct Evidence of Unconventional Superconductivity in Doped Kagome system RV$_3$Sb$_5$
University of Illinois at Urbana-Champaign(伊利诺伊大学厄巴纳-香槟分校);Karlsruhe Institute of Technology(卡尔斯鲁厄理工学院);University of California Santa Barbara(加州大学圣塔芭芭拉分校)