We propose that the observed splitting of the vortices in the cuprates into fractional vortices (partons) may be of static rather than of dynamic origin. This interpretation is backed by a study of a model with a dominant d-wave and subdominant s-wave pairing interaction. We find that the vortex may split into two partons, both of which carry one half of the magnetic flux quantum. The partons are hold together by a confining string along which the phase jumps approximately by pi and their equilibrium distance increases with lowering the energy difference epsilon between the pairing states. The partons become deconfined at the critical point where epsilon vanishes.
The vortex transport entropy in the mixed state of the cuprate superconductors YBa$_2$Cu$_3$O$_{7-δ}$ and Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$ at the maximum Nernst or Ettingshausen signal below $T_c$ is discussed. The vortex transport entropy per CuO$_2$ double layer in the cuprate epitaxial films is found to be close to the Boltzmann constant.
A unified model of vortex tangles is proposed to describe unconventional transport in cuprate high-temperature superconductors, which not only captures the fast vortices scenario at low density, but also predicts a novel mechanism of core-core collisions in dense vortex fluid regime. The theory clarifies the nature of vortex fluctuations being the quantum fluctuations of holes and then resolves a discrepancy of two orders of magnitude of Anderson's damping model $\hbar n_v$, with right prediction of the nonlinear field dependence of the resistivity $ρ=ρ_n(B+B_T)/(B_0+B+B_T)$ and the Nernst eff…
We present a possible explanation for a recently observed magnetic field induced charge order in cuprate superconductors (Edkins et al.~arXiv:1802.04673 [cond-mat.supr-con]). We argue that it arises from the reorganization of spin-vortex-induced loop current (SVILC) pattern due to supercurrent-flow caused by the magnetic field. The reorganization is from the most stable tiling of $4a times 6a$ spin-vortex quartets ($a$ is the lattice constant in the CuO$_2$ plane, and a spin-vortex quartet is stable of unit of spin-vortices that contains four holes, four spin-vortices, and four SVILCs) to that…
By using a high quality Tl2Ba2Ca2Cu3O10 (Tl-2223) single crystal as an example, the magnetization vector was probed in the reversible region of highly anisotropic cuprate superconductors. For that, we have measured its components along and transverse to the applied magnetic field for different crystal orientations. The analysis shows that the angular dependence of the perpendicular component of the magnetization vector follows the one predicted by a London-like approach which includes a contribution associated with the thermal fluctuations of the 2D vortex positions. For the Tl-2223 crystal st…
Using sound velocity and attenuation measurements in high magnetic fields, we identify a new transition in the vortex lattice state of La$_{2-x}$Sr$_{x}$CuO$_4$ (LSCO). The transition, observed in magnetic fields exceeding 35 T and temperatures far below zero field $T_c$, is detected in the compression modulus of the vortex lattice, at a doping level $x=p=0.17$. Our theoretical analysis based on Eilenberger theory of vortex lattice shows that the transition corresponds to the long-sought 45 degrees rotation of the square vortex lattice, predicted to occur in $d$-wave superconductors near a van…
We present measurements of the fluctuation superconductivity in an underdoped thin film of La$_{1.905}$Sr$_{0.095}$CuO$_4$ using time-domain THz spectroscopy. We compare our results with measurements of diamagnetism in a similarly doped crystal of La$_{2-x}$Sr$_x$CuO$_4$. We show through a vortex-plasma model that if the fluctuation diamagnetism solely originates in vortices, then they must necessarily exhibit an anomalously large vortex diffusion constant, which is more than two orders of magnitude larger than the Bardeen-Stephen estimate. This points to either the extremely unusual propertie…
The Onsager rule determines the frequencies of quantum oscillations in magnetic fields. We show that this rule remains intact to an excellent approximation in the mixed-vortex state of the underdoped cuprates even though the Landau level index $n$ may be fairly low, $n\sim 10$. The models we consider are fairly general, consisting of a variety of density wave states combined with $d$-wave superconductivity within a mean field theory. Vortices are introduced as quenched disorder and averaged over many realizations, which can be considered as snapshots of a vortex liquid state. We also show that…
Vortex state microwave response in superconducting cuprates and MgB$_2$
研究了YBaPDMATHABMM Cu $_{3}$ O $_{7-δ}$、SmBaPDMATHABMM Cu $_{3}$ O $_{7-δ}$和MgB $_{2}$在涡旋态下的微波响应物理.我们首先回顾了在伦敦极限下涡旋态微波响应的理论基础。然后，我们提出了一个广泛的测量领域，温度和频率依赖性的涡旋态微波复电阻率在超导薄膜，测量谐振腔和扫频Corbino磁盘。这些技术的组合允许在这些创新的超导体中的涡旋状态的微波响应的全面描述。在所有材料的调查，我们表明，单独的磁通量运动不能考虑到所有观察到的实验特征，无论是在频率，也不是在外地的依赖性。这种差异可以通过考虑准粒子对涡旋态响应的贡献（通常被忽略）来解决。奇特的，虽然不同的，这里考虑的超导材料的物理学，即两个带超导在MgB $_{2}$和超导能隙与线的节点在铜酸盐，引起一个大幅度增加的贡献准粒子场相关的微波响应。通过对实验数据的综合分析，可以提取或推断出许多与涡旋态有关的有趣的物理量，如涡旋频率和涡旋粘度随温度的变化，准粒子密度随场的变化，MgB $_{2}$中$σ$带超流密度随温度的变化等
We investigated the nature of the quasi-particle state in the vortex core by means of the flux-flow Hall effect measurements at 15.8 GHz. We measured the flux-flow Hall effect in cuprate superconductors, Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{y}$ and YBa$_{2}$Cu$_{3}$O$_{y}$ single crystals, whose equilibrium $B$-$T$ phase diagrams were different. As a result, we found that the Hall angle is independent of the magnetic field, and reaches an order of unity at low temperatures in BSCCO. However, in YBCO, the angle increases with increasing magnetic field even at low temperatures. We understood that this …
When very high magnetic fields suppress the superconductivity in underdoped cuprates, an exceptional new electronic phase appears. It supports remarkable and unexplained quantum oscillations and exhibits an unidentified density wave (DW) state. Although generally referred to as a "charge" density wave (CDW) because of the observed charge density modulations, theory indicates that this could actually be the far more elusive electron-pair density wave state (PDW). To search for evidence of a field-induced PDW in cuprates, we visualize the modulations in the density of electronic states $N(\bf{r}…
A central question in the underdoped cuprates pertains to the nature of the pseudogap ground state. A conventional metallic ground state of the pseudogap region has been argued to host quantum oscillations upon destruction of the superconducting order parameter by modest magnetic fields. Here we use low applied measurement currents and millikelvin temperatures on ultra-pure single crystals of underdoped YBa$_2$Cu$_3$O$_{6+x}$ to unearth an unconventional quantum vortex matter ground state characterized by vanishing electrical resistivity, magnetic hysteresis, and non-ohmic electrical transport…
The recent detection of charge-density modulations in YBa2Cu3Oy and other cuprate superconductors raises new questions about the normal state of underdoped cuprates. In one class of theories, the modulations are intertwined with pairing in a dual state, expected to persist up to high magnetic fields as a vortex liquid. In support of such a state, specific heat and magnetisation data on YBa2Cu3Oy have been interpreted in terms of a vortex liquid persisting above the vortex-melting field Hvs at T = 0. Here we report high-field measurements of the electrical and thermal Hall conductivities in YBa…
Doping dependence of the vortex-core energy in bilayer films of cuprates
产生涡旋核所需的能量是解决欠掺杂铜酸盐中热涡旋波动物理学的基本成分。在这里，我们从理论上研究它的作用的发生Beresinskiii-Kosterlitz-无相变的双层膜的不均匀性。通过与Hetel等人[Nat.Phys.3，700（2007）]对Y $_{1-x}$ Ca $_{x}$ Ba $_{2}$ Cu $_{3}$ O $_{7-\d}$（YBCO）的两个晶胞薄膜中的穿透深度的最新测量的比较，我们可以提取涡旋芯能量$μ$的值，并且表明在低掺杂下$μ$与$T_c$线性地成比例。
The phase diagram of the superconducting cuprates is often used to show how their electronic properties change as a function of the mean doping level, i.e., the average hole content of the CuO$_2$ plane. In Nuclear Magnetic Resonance (NMR) experiments average doping, as well as the distribution of these holes between planar Cu and O reveals itself through the quadrupole splittings of the $^{63,65}$Cu and $^{17}$O NMR. Here we argue based on all published NMR data available to us in favor a new type of phase diagram that has the planar oxygen quadrupole splitting and with it the planar oxygen h…
Mixed-state microwave response in superconducting cuprates
本文报道了RE Ba $_{2}$ Cu $_{3}$ O $_{7-δ}$薄膜（RE = Y，Sm）的磁场感生微波复电阻率的测量结果。在48 GHz下通过端壁替换配置中的谐振腔进行测量。的磁场的依赖性进行了研究，通过施加一个中等（0.8 T）的磁场沿c轴。在已知的涡旋动力学模型内分析了YBa $_{2}$ Cu $_{3}$ O $_{7-δ}$和SmBa $_{2}$ Cu $_{3}$ O $_{7-δ}$中测量的涡旋态复电阻率。结果表明，归因于所观察到的响应涡运动单独导致不一致的确定涡参数（如涡粘度和钉扎常数）。相比之下，归因于整个响应场致对断裂导致的数据几乎定量的描述。
Superlattice of spin vortices has been proposed in an earlier article as an alternative to the stripe interpretation of spin modulations in 1/8-doped lanthanum cuprates. The present article addresses several additional characteristics of the spin vortex lattice, namely: (i) the nature of extended charge states; (ii) the position of neutron spin peaks as a function of doping; and (iii) the absence of higher order spin harmonics. All these characteristics afford straightforward connection to the experimental results produced by angle-resolved photoemission spectroscopy, resistivity measurements,…
Magnetic-force-microscope study of interlayer "kinks" in individual vortices in underdoped cuprate YBa$_2$Cu$_3$O$_{6+x}$ superconductor
我们使用磁力显微镜的图像和操纵个别涡线线程单晶YBa $_2$铜$_3$ O $_{6.4}$，层状超导体。我们发现，当我们拉动一个固定涡的顶部时，它可能不会平滑地倾斜。有时，我们观察到一个漩涡分裂成离散的片段，可以描述为短叠的煎饼漩涡，类似于Benkraouda和Clem提出的“扭结”结构。定量分析给出了钉扎力和堆叠之间的耦合的估计。我们的测量突出了分层超导体中煎饼涡旋堆叠的离散性。
Some Considerations on the Additional Absorption Peak in the c-axis Conductivity of Bilayer Cuprate Superconductors: Interpretation of the Changes Induced by a Parallel Magnetic Field and the Role of Bilayer Splitting
Kojima等人报道的在平行磁场作用下，低掺杂YBa 2 Cu 3 O 6. 6的c轴电导率的400 cm^{-1}峰的变化与超流峰的模型一致。我们的计算结果的c-轴响应的双层化合物具有明确的双层分裂带的介绍和讨论。对于中等值的双层分裂（Δ E相当于2 Delta_{max}）的超导态的光谱表现出额外的模式，这是由于冷凝和类似的早期的唯象方法之一。
We propose a new magnetic phase diagram of La2-xSrxCuO4 around a quantum critical point x = 1/9 based on field-cooled magnetization measurements and critical fittings. A new phase boundary Tm2(H) is discovered which buries deeply below the first order vortex melting line in the vortex solid phase. The coupling between superconductivity and antiferromagnetism is found to be attractive below Tm2(H) while repulsive above. The attractive coupling between superconducting order and static antiferromagnetic order provides compelling experimental evidence that the antiferromagnetism microscopically co…
Second magnetization peak (SMP) in hole-doped cuprates and iron pnictide superconductors has been widely explored. However, similar feature in the family of electron-doped cuprates is not common. Here, we report the vortex dynamics study in the single crystal of an electron-doped cuprate Pr$_{0.87}$LaCe$_{0.13}$CuO$_4$ superconductor using dc magnetization measurements. A SMP feature in the isothermal $M(H)$ was observed for $H$$\parallel$$ab$-planes. On the other hand, no such feature was observed for $H$$\parallel$$c$-axis in the crystal. Using magnetic relaxation data, a detailed analysis o…
We propose a simple experiment to determine whether vortices persist above the superconducting transition temperature Tc in the pseudogap phase of high temperature cuprate superconductors. This involves using a magnetic dot to stabilize a vortex in a thin cuprate film beneath the dot. We calculate the magnetic field profile as a function of distance from the dot if a vortex is present, and discuss possible measurements that could be done to detect this. Finally, we comment on the temperature range where a stable vortex should be observable.
The distinct distribution of local magnetic fields due to superconducting vortices can be detected with nuclear magnetic resonance (NMR) and used to investigate vortices and related physical properties of extreme type II superconductivity. This review summarizes work on high temperature superconductors (HTS) including cuprates and pnictide materials. Recent experimental results are presented which reveal the nature of vortex matter and novel electronic states. For example, the NMR spectrum has been found to provide a sharp indication of the vortex melting transition. In the vortex solid a freq…
Key properties of the cuprates, such as the pseudogap observed above the critical temperature $T_c$, remain highly debated. Given their importance, we recently proposed a novel mechanism based on the Bose-like condensation of mutually interacting Cooper pairs [W. Sacks, A. Mauger, Y. Noat, Superconduct. Sci. Technol. 28 105014, (2015)]. In this work, we calculate the temperature dependent DOS using this model for different doping levels from underdoped to overdoped. In all situations, due to the presence of excited pairs, a pseudogap is found above $T_c$ while the normal DOS is recovered at $T…
The phase diagram of underdoped cuprates in a magnetic field ($H$) is the key ingredient in understanding the anomalous normal state of these high-temperature superconductors. However, the upper critical field ($H_{c2}$) or the extent of superconducting phase with vortices, a type of topological excitations, and the role of charge orders that are present at high $H$, remain under debate. We address these questions by studying stripe-ordered La-214, i.e. cuprates in which charge orders are most pronounced and zero-field transition temperatures $T_{c}^{0}$ are lowest; the latter opens a much lar…
Disorder can have remarkably disparate consequences in superconductors, driving superconductor-insulator transitions in ultrathin films by localizing electron pairs and boosting the supercurrent carrying capacity of thick films by localizing vortices (magnetic flux lines). Though the electronic 3D-to-2D crossover at material thicknesses $d \sim ξ$ (coherence length) is well studied, a similarly consequential magnetic crossover at $d \sim L_c$ (pinning length) that should drastically alter material properties remains largely underexamined. According to collective pinning theory, vortex segments…
The design of artificial vortex pinning landscapes is a major goal towards large scale applications of cuprate superconductors. While disordered nanometric inclusions have shown to modify their vortex phase diagram and to produce enhancements of the critical current1,2, the effect of ordered oxide nanostructures remains essentially unexplored. This is due to the very small nanostructure size imposed by the short coherence length, and to the technological difficulties in the nanofabrication process. Yet, the novel phenomena occurring at oxide interfaces open a wide spectrum of technological opp…
