We analyse the combined effect of orbital and Pauli depairing on the superconducting state, and apply the results to the heavy fermion CeCoIn$_5$. We find that: a) standard extrapolation based on the slope of $H_{c2}(T)$ in the vicinity of the transition temperature to T=0 does not always give accurate values of the orbital upper critical field; b) critical value of the Maki parameter, $α$, that determines onset of the first order transition depends on the Fermi surface shape and the symmetry of the gap, and is $α^*\approx 3$ for CeCoIn$_5$; c) the anisotropy of the thermodynamic and transport coefficients in the low-temperature, low-field part of the phase diagram is essentially insensitive to the Zeeman field and can be used to determine the nodal directions in Pauli-limited superconductors. The latter result confirms the finding of the $d_{x^2-y^2}$ order parameter CeCoIn$_5$.
We have used small-angle neutron scattering to determine the vortex lattice phase diagram in the topological superconductor UPt3 for the applied magnetic field along the crystalline c-axis. A triangular vortex lattice is observed throughout the superconducting state, but with an orientation relative to the hexagonal basal place that changes with field and temperature. At low temperature, in the chiral B phase, the vortex lattice undergoes a non-monotonic rotation with increasing magnetic field. The rotation amplitude decreases with increasing temperature and vanishes before reaching the A phas…
Simultaneous Evidence for Pauli Paramagnetic Effects and Multiband Superconductivity in KFe$_2$As$_2$ by Small-Angle Neutron Scattering Studies of the Vortex Lattice
我们研究了KFe $_2$ As $_2$中超导态的内禀各向异性。当外加磁场向FeAs晶面旋转时，利用小角中子散射对涡旋晶格成像。各向异性被发现是强烈的场依赖性，表明多带超导性。此外，高场各向异性显着超过上临界场，提供进一步的支持泡利限制在KFe $_2$作为$_2$中施加在基面的字段。泡利顺磁性对涡核中未成对准粒子的影响直接从纵向和横向涡旋晶格场调制引起的散射强度的比值中表现出来。
Anisotropy of Vortex-Liquid and Vortex-Solid Phases in Single Crystals of Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$: Violation of the Scaling Law
本文采用Corbino几何方法研究了倾斜磁场中Bi $_2$ Sr $_2$ CaCu $_2$ O $_{8+δ}$单晶的涡旋液相和涡旋固相。结果表明，涡旋固相的各向异性随温度的升高而增大，并在$T\approx 0.97 T_c$处达到最大值。相反，涡旋液体的各向异性在整个测量温度范围内单调上升。所观察到的行为进行了讨论的背景下，在强分层系统中的涡的尺寸交叉和热波动。
Superconducting vortex cores have been extensively studied for magnetic fields applied perpendicular to the surface by mapping the density of states (DOS) through Scanning Tunneling Microscopy (STM). Vortex core shapes are often linked to the superconducting gap anisotropy---quasiparticle states inside vortex cores extend along directions where the superconducting gap is smallest. The superconductor 2H-NbSe$_2$ crystallizes in a hexagonal structure and vortices give DOS maps with a sixfold star shape for magnetic fields perpendicular to the surface and the hexagonal plane. This has been associ…
Non-exponential London penetration depth in RFeAsO$_{0.9}$F$_{0.1}$ (R=La,Nd) single crystals
测量了RFeAsO $_{0.9}$ F $_{0.1}$（R=La，Nd）单晶（R-1111）的超导穿透深度$λ(T)$。在Nd-1111中，我们发现$λ(T)$在冷却时出现了一个上升，并将其归因于Nd离子的顺磁性，类似于电子掺杂的铜酸盐Nd-Ce-Cu-O的情况。经过顺磁性校正后，发现伦敦穿透深度变化遵循幂律行为，在低温下为$Δλ_L(T)\propto T^{2}$。在非磁性La-1111晶体中发现了与$λ(T)$相同的$T^2$变化。在整个温度范围内的超流密度和渗透深度各向异性的分析是一致的双间隙超导。在此基础上，结合我们以前的工作，我们得出结论：RFeAsO（1111）和BaFe $_2$ As $_2$（122）族磷属元素化物超导体都具有非常规的双能隙超导性。
Directional pinning and anisotropy in YBa2Cu3O7-x with BaZrO3 nanorods: intrinsic and nanorods-induced anisotropy
研究了在倾斜磁场作用下，含BaZrO 3纳米棒的YBa 2 Cu 3 O 7-x薄膜在涡旋态下的微波复电阻率.给出了涡旋粘性$η$、钉扎常数k_p和蠕变因子χ_M的上限随角度的变化关系。我们发现，纳米棒的方向效应在η中是不存在的，这是由质量各向异性γ决定的。相比之下，钉扎介导的性质受到纳米棒的强烈影响。重要的是，受纳米棒影响的钉扎和蠕变在我们非常高的工作频率下也是可检测的，这意味着涡旋从其平衡位置的非常短的位移。
Magnetic field-dependence of the basal-plane superconducting anisotropy in YBa2Cu4O8 from small-angle neutron scattering measurements of the vortex lattice
我们报道了欠掺杂YBa $_{2}$ Cu $_{4}$ O $_{8}$（Y 124）超流密度的基面各向异性的研究，显示了CuO $_{2}$面和完全占据的CuO链的影响.从涡旋晶格的小角中子散射测量，我们可以推断温度（$T$）范围$T=$ 1.5 K至$T_{\rm c}$和磁感应强度$B$从0.1 T至6 T的超导（SC）性质。我们发现，沿\textbf{a}的超流密度有一个简单的$d$波T-依赖。然而，沿着\textbf{b}（链方向），超流密度随着$T$和场的增加而下降得更快。这强烈地暗示了邻近效应诱导的CuO链中的超导电性的抑制。此外，我们的研究结果不支持一个共同的框架，低场平面SC响应在Y 124和相关的YBa $_{2}$ Cu $_{3}$ O $_{7}$，也表明，任何磁场诱导的电荷密度波秩序在Y 124只存在于6 T以上的领域。
Unusual magneto-transport of YBa2Cu3O7-d films due to the interplay of anisotropy, random disorder and nanoscale periodic pinning
我们研究了一个流形的相互作用的弹性线的空间相关性的强烈影响随机和有序钉扎之间的竞争的一般问题。这是通过磁输运实验与YBa 2 Cu 3 O 7-d薄膜，包含一个周期性的涡旋钉扎阵列通过掩蔽离子照射，除了本地随机钉扎。我们观察到的强场匹配效应表明周期性钉扎的普遍存在，并表明在匹配场中每条涡旋线都束缚在人为钉扎位点上。然而，涡玻璃化转变的维度，准2D而不是通常的3D，证据减少沿涡线的涡玻璃相关性。这也支持了一个不寻常的角度依赖的磁阻，这大大不同于玻色玻璃系统。角磁阻的定量分析使我们能够将这种行为与系统各向异性的增强联系起来，这是离子辐照的附带效应。
The magnetic penetration depth anisotropy $γ_λ=λ_{c}/λ_{ab}$ ($λ_{ab}$ and $λ_{c}$ are the in-plane and the out-of-plane components of the magnetic penetration depth) in a CaKFe$_4$As$_4$ single crystal sample (the critical temperature $T_{\rm c}\simeq 35$ K) was studied by means of muon-spin rotation ($μ$SR). $γ_λ$ is almost temperature independent for $T\lesssim 20$ K ($γ_λ\simeq 1.9$) and it reaches $\simeq 3.0$ by approaching $T_{\rm c}$. The change of $γ_λ$ induces the corresponding rearrangement of the flux line lattice (FLL), which is clearly detected via enhanced distortions of the FLL…
Scaling behavior of the crossover to short-stack regimes of Josephson vortex lattices in Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ stacks
本文系统地研究了具有不同几何形状和超导各向异性参数的Bi $_2$ Sr $_2$ CaCu $_2$ O $_{8+δ}$微制造结中约瑟夫森涡旋（JV）流阻的振荡。当平行于$ab$平面的外加磁场增加时，具有对应于$ϕ_0/2$ par原子约瑟夫森结的周期的振荡变为具有双倍周期的振荡。该交叉由结长度和各向异性参数两者缩放，表明有利于三角形JV晶格的体电感耦合被替换为JV晶格的占主导地位的相互作用的表面变形能。这些结果表明，在较小且各向异性更强的样品中，在较高的磁场下，同相正方形JV晶格明显。
Anisotropy effects on flux pinning and flux flow are strongly effective in cuprate as well as iron-based superconductors due to their intrinsically layered crystallographic structure. However $\textrm{Fe(Se,Te)}$ thin films grown on $\textrm{CaF}_2$ substrate result less anisotropic with respect to all the other iron based superconductors. We present the first study on the angular dependence of the flux flow instability, which occurs in the flux flow regime as a current driven transition to the normal state at the instability point ($I^*$,$V^*$) in the current-voltage characteristics. The volt…
Effect of varying material anisotropy on critical current anistropy in vicinal YBa$_2$Cu$_3$O$_{7-δ}$ thin films
高$T_{c}$铜氧化物超导体以其各向异性层状结构而闻名，某些材料确实趋向于Lawrence-Doniach超导体的极限。然而，YBa $_2$ Cu $_3$ O $_{7-δ}$具有比从其层间距预期的更小的各向异性。这是由于结构中的铜酸盐链。为了研究链氧对输运性质的影响，对完全氧化和脱氧的YBa $_2$ Cu $_3$ O $_{7-δ}$薄膜和最佳氧化的Y $_{0.75}$ Ca $_{0.2}$ Ba $_2$ Cu $_3$ O $_{7-δ}$薄膜进行了临界电流与外加场角的测量。在10个$^{\circ}$错切SrTiO $_3$衬底上生长薄膜，以观察到本征涡旋沟道效应。在依赖于场角的临界电流的研究中观察到的膜的涡旋沟道最小的形式被认为取决于膜氧化。涡流沟道效应取决于到弦-饼磁通线晶格的角相关交叉。所获得的结果似乎与Blatter等人的预测一致[Rev. Mod. Phys.，66（4）：1125（1994）]，增加的超导各向异性导致在较小的角度范围内存在扭结的弦-饼晶格。
