The Tomasch effect (TE) is due to quasiparticle interference (QPI) as induced by a nonuniform superconducting order parameter, which results in oscillations in the density of states (DOS) at energies above the superconducting gap. Quantum confinement in nanoscale superconductors leads to an inhomogenerous distribution of the Cooper-pair condensate, which we found triggers the manifestation of a new TE. We investigate the electronic structure of the nanoscale superconductors by solving the Bogoliubov-de Gennes (BdG) equations self-consistently and obtain the TE determined by two types of processes, involving two or three particle QPIs. Both types of QPIs result in additional BCS-like Bogoliubov-quasiparticles and BCS-like energy gaps leading to oscillations in the DOS and modulated wave patterns in the local density of states. These effects are strongly related to the symmetries of the system. A reduced $4 \times 4$ inter-subbands BdG Hamiltonian is established in order to describe analytically the TE of two-QPIs. Our study is relevant to nanoscale superconductors, either nanowires or thin films, Bose-Einsten condensates and confined systems such as two-dimensional electron gas interface superconductivity.
Nanoscale phase separation of antiferromagnetic order and superconductivity in K$_{0.75}$Fe$_{1.75}$Se$_2$
本文报道了铁硒化物超导体K $_{0.75}$ Fe $_{1.75}$ Se $_2$的面内光谱研究。测量结果表明，在T $_c$以下，在相对非相干的电子背景下，在比超导能隙小得多的频率下，出现了尖锐的反射边，这是迄今为止在任何其他铁基超导体中都没有看到的现象。此外，该特征可以被显著抑制并通过适度的磁场向较低频率偏移。我们的分析表明，这种边缘结构产生的约瑟夫森耦合等离子体激元的超导冷凝的发展。结合透射电子显微镜分析，我们的研究为超导性和磁性之间存在纳米级相分离提供了令人信服的证据。这些结果也使我们能够理解从不同技术探测到的各种看似有争议的实验数据。
Nanoscale interplay of strain and doping in a high-temperature superconductor
最高温度的超导体在纳米尺度上是电子不均匀的，这表明存在一个局部变量，可以利用它来增强超导配对。本文报道了铜氧化物超导体Bi $_2$ Sr $_2$ CaCu $_2$ O $_{8+x}$中局域掺杂与局域应变之间的关系。我们使用扫描隧道显微镜发现，关键的氧掺杂剂是周期性分布的，与局部应变。我们的所有氧掺杂剂的单位细胞内的位置的皮尺度调查提供了一个完整的微观理论的基本结构输入。
Nanoscale Surface Element Identification and Dopant Homogeneity in the High-$T_c$ Superconductor Pr$_x$Ca$_{1-x}$Fe$_2$As$_2$
我们使用扫描隧道显微镜来确定Pr $_x$ Ca $_{1-x}$ Fe $_2$ As $_2$的表面结构和掺杂剂分布，$_2$是铁基超导体122家族的最高- $T_c$成员。我们通过映射与功函数相关的局部隧穿势垒高度来确定解理表面终止。我们的图像个别Pr掺杂剂负责超导性，并表明，他们不集群，但实际上在短的长度尺度互相排斥。因此，我们认为，低体积分数的高- $T_c$超导相是不可能起源于Pr的不均匀性。
Hysteretic vortex matching effects in high-$T_c$ superconductors with nanoscale periodic pinning landscapes fabricated by He ion beam projection technique
The current density in a superconductor with turnarounds or constrictions is non-uniform due to a geometrical current crowding effect. This effect reduces the critical current in the superconducting structure compared to a straight segment and is of importance when designing superconducting devices. We investigate the current crowding effect in numerical simulations within the generalized time-dependent Ginzburg-Landau (GTDGL) model. The results are validated experimentally by measuring the magnetic field dependence of the critical current in superconducting nanowire structures, similar to tho…
Although nanoscale deformation, such as nanostrain in iron chalcogenide (FeSexTe1-x, FST) thin films, has attracted attention owing to the enhancement of general superconducting properties, including critical current density (Jc) and critical transition temperature, its formation has proven to be an extremely challenging and complex process thus far. Herein, we successfully fabricated an epitaxial FST thin film with uniformly distributed nanostrain by injection of a trace amount of CeO2 inside FST matrix using sequential pulsed laser deposition. Using transmission electron microscopy and geome…
When the electron density of highly crystalline thin films is tuned by chemical doping or ionic liq- uid gating, interesting effects appear including unconventional superconductivity, sizeable spin-orbit coupling, competition with charge-density waves, and a debated low-temperature metallic state that seems to avoid the superconducting or insulating fate of standard two-dimensional electron systems. Some experiments also find a marked tendency to a negative electronic compressibility. We suggest that this indicates an inclination for electronic phase separation resulting in a nanoscopic inhomo…
Stripe-like nanoscale structural phase separation and optimal inhomogeneity in superconducting BaPb$_{1-x}$Bi$_x$O$_3$
在超导BaPb $_{1-x}$ Bi $_x$ O $_3$中观察到了部分无序条纹形式的结构相分离，其特征长度尺度在纳米范围内。超导相干长度的演变与组合物相对于这些条纹的大小表明在确定超导圆顶的形状的纳米结构的重要作用。提出最大值$T_c$由一种“最佳不均匀性”决定，其特征是从一个不均匀的宏观超导体到一个颗粒状超导体的交叉，对于这种交叉，相位涨落抑制了$T_c$ .
The transverse (Hall) voltage in thin films of the high-temperature superconductor YBa$_{2}$Cu$_{3}$O$_{7-δ}$ with an artificial periodic pinning array is investigated. Columnar defect regions along the crystallographic $c$ axis, in which superconductivity is suppressed, are created by irradiation with He$^+$ ions through a silicon stencil mask. The commensurate arrangement of magnetic flux quanta with the artificial defect lattice is confirmed by maxima of the critical current and minima of the resistance, respectively. The magnetic field dependence of the transverse voltage reveals a commens…
Nanoscale ferroelectric manipulation of magnetic flux quanta
利用大极化铁电体（BiFeO 3）和高温超导体（YBa 2 Cu 3 O 7-δ）的异质结构，我们证明了铁电场效应对超导凝聚体的纳米尺度调制。通过这种机制，可以在超导体中创建模仿铁电畴结构的正常区域的纳米级图案。这产生了磁通量量子的能量景观，并进而将局部铁电极化耦合到局部磁感应。我们表明，这种形式的磁电耦合，连同可逆设计的铁电畴结构的可能性，允许静电操纵的磁通量量子。
Local and fast structural probes using synchrotron radiation have shown nanoscale striped puddles and nanoscale phase separation in doped perovskites.It is known that the striped phases in doped perovskites are due to competing interactions involving charge, spin and lattice degrees of freedom,but while many theoretical models for spin and charge stripes have been proposed we are missing theoretical models describing the complex lattice striped modulations in doped perovskites. In this work we show that two different stripes can be represented as a superposition of a pair of stripes, U(theta_n…
