We develop a theory of conductivity of type-II superconductors in the flux flow regime taking into account random spatial fluctuations of the system parameters, such as the gap magnitude $Δ$(r) and the diffusion coefficient D(r). We find a contribution to the conductivity that is proportional to the inelastic relaxation time $τ_{in}$, which is much longer than the elastic relaxation time. This new contribution is due to Debye-type relaxation, and it can be much larger than the conventional flux flow conductivity due to Bardeen and Stephen. The new contribution is expected to dominate in clean superconductors at low temperatures and in magnetic fields much smaller than $H_{c2}$.
Motivated by Sr2RuO4, we consider a chiral superconductor where the gap is strongly suppressed along certain momentum directions. We evaluate the thermal Hall conductivity in the gapless regime, i.e., at temperature small compared with the impurity band width γ, taking the simplest model of isotropic impurity scattering. We find that, under favorable circumstances, this thermal Hall conductivity can be quite significant, and is smaller than the diagonal component (the universal thermal conductivity) only by a factor of 1/ ln(2 Δ_M/γ), where Δ_M is the maximum gap.
We propose a model and derive analytical expressions for conductivity in heterogeneous fully anisotropic conductors with ellipsoid superconducting inclusions. This model and calculations are useful to analyze the observed temperature dependence of conductivity anisotropy in various anisotropic superconductors, where superconductivity onset happens inhomogeneously in the form of isolated superconducting islands. The results are applied to explain the experimental data on resistivity above the transition temperature $T_c$ in the high-temperature superconductor $\mathrm{YBa_2Cu_4O_8}$ and in the …
Conventional BCS superconductors are expected to exhibit a conductivity with vanishing dissipation with decreasing temperature. While bulk physical properties measurements indicate PdPb$_{2}$ is a conventional superconductor with a $T_c$ of 3.0 K, measurements of surface impedance through the microwave cavity perturbation technique indicate a large, non-vanishing dissipative component below $T_c$ that is at odds with conventional superconductivity. We demonstrate PdPb$_2$ to be a possible topological superconductor with a fully gapped bulk and a dissipative Majorana fluid surface.
Recently Deyo et al. [\prb {\bf 106}, 104502 (2022)] suggested that the surface resistance $R_s(H_0)$ of a superconductor under strong electromagnetic field can be affected by field-induced quasiparticle bound states at the surface. This Comment shows that the existence of such bound states and their contribution to $R_s$ are not substantiated and the phenomenological models of Ref. \cite{corn} give incorrect field and temperature dependencies of $R_s(T,H_0)$.
The thermal fluctuations contribution to magnetization and magneto-conductivity of type II layered superconductor is calculated in the framework of Lawrence-Doniach model. For numerous high temperature cuprate superconductors, it was discovered that the magnetization dependence on temperature in wide range of fields exhibits an intersection point at a temperature slightly below $T_{c}$. We notice a similar intersection point of the magneto-conductivity curves at the approximate same temperature. The phenomenon is explained by strong (non-gaussian) thermal fluctuations with interactions treated…
We study the dc conductivity of iron-based superconductors within the orbital-selective spin fluctuation scenario. Within this approach, the anisotropy of spin fluctuations below the spin-nematic transition at T$_S$ is also responsible for the orbital ordering, induced by nematic self-energy corrections to the quasiparticle dispersion. As a consequence, the anisotropy of the dc conductivity below T$_S$ is determined not only by the anisotropy of the scattering rates as expected within a spin-nematic scenario, but also by the modification of the Fermi velocity due to the orbital reconstruction.…
In most superconductors, optical excitations require impurity scattering or the presence of multiple bands. This is because in clean single-band superconductors, the combination of particle-hole and inversion symmetries prevents momentum-conserving transitions. In this work we show how the flow of supercurrent can lead to new contributions to optical conductivity. As supercurrent breaks inversion symmetry, transitions across the superconducting gap become allowed even in clean superconductors and dominate over impurity-induced contributions for energies comparable to the gap width. The respons…
Complex conductivity in strongly fluctuating layered superconductors
本文用含时的Ginzburg-Landau方法计算了磁场作用下层状第二类超导体的复涨落电导率。超导体的层状结构由Lawrence-Doniach模型解释，而动力学中的非线性相互作用项在自洽高斯近似下处理。在高$T_{c}$材料中，$H-T$图的大部分属于涡旋液相。给出了所有朗道能级贡献之和的显式表达式，该表达式基本上适用于整个相，并与高$T_{c}$超导体$_{2}$ $_{3}$ O $_{7-δ}$的实验数据进行了比较.以上的交叉到“正常相”，我们的结果与以前得到的一致。
Time-resolved optical conductivity is an oft-used tool to interrogate quantum materials driven out of equilibrium. Theoretically calculating this observable is a complex topic with several approaches discussed in the literature. Using a non-equilibrium Keldysh formalism and a functional derivative approach to the conductivity, we present a comparison of two particular approaches to the calculation of the optical conductivity, and their distinguishing features, as applied to a pumped superconductor. The two methods are distinguished by the relative motion of the probe and gate times; either the…
Microwave Conductivity of a High Purity d-wave Superconductor
尖状行为的微波电导率观察到在清洁的ortho-II YBPDMATHABMM铜$_{3}$ O $_{6.50}$在低温和低频率的杂质散射率的频率依赖性与一个可忽略的小值在零频率直接相关。在弱散射极限下，电导率随频率线性下降。在涡旋状态，假设一个随机（高斯）分布的旋涡，我们表明，磁场深刻地改变了杂质散射率，现在获得一个有限的零频率值。因此，我们预测在低频下的微波电导率的德鲁德线形状。
Microwave Conductivity due to Scattering from Extended Linear Defects in d-Wave Superconductors
最近的微波电导率测量的解孪晶，高纯度，稍微过掺杂的YBa $_{2}$ Cu $_{3}$ O $_{6.993}$晶体揭示了一个线性的温度依赖性和近Drude线的形状的温度之间的1和20 K和频率范围从1到75 GHz。先前的理论工作表明，d波超导体中点缺陷（杂质）散射的简单模型与这些结果不一致。因此，有人建议，散射扩展缺陷，如孪晶界残留物，从退孪过程中留下的，也可能是重要的。我们计算的自洽玻恩近似（包括顶点校正）的d-波超导体中存在的散射从扩展的线性缺陷的自能和微波电导率。我们发现，在实验相关的限制（$Ω, 1/τ\ll T \ll Δ_{0}$），由此产生的微波电导率有一个线性的温度依赖性和一个近Drude频率依赖性，符合实验。
We use the formerly derived explicit analytical expressions for the conductivity of nanostructured superconductors supercooled below the critical temperature in electric field. Computer simulations reveal that the negative differential conductivity region of the current-voltage characteristic leads to excitation of electric oscillations. We simulate a circuit with distributed elements as a first step to obtain gigahertz oscillations. This gives a hint that a hybrid device of nanostructured superconductors will work in terahertz frequencies. If the projected setup is successful, we consider the…
In the framework of Keldysh-Usadel kinetic theory, we study the temperature dependence of flux-flow conductivity (FFC) in diffusive superconductors. By using self-consistent vortex solutions we find the exact values of dimensionless parameters that determine the diffusion-controlled FFC both in the limit of the low temperatures and close to the critical one. Taking into account the electron-phonon scattering we study the transition between flux-flow regimes controlled either by the diffusion or the inelastic relaxation of non-equilibrium quasiparticles. We demonstrate that the inelastic electr…
The interplay between the thermal transport property and the topological aspect is investigated in a spin-triplet chiral p-wave superconductor Sr2RuO4 with the strong two-dimensionality. We show the thermal Hall conductivity is well described by the temperature linear term and the exponential term in the low temperature region. While the former term is proportional to the so-called Chern number directly, the latter is associated with the superconducting gap amplitude of the gamma band. We also demonstrate that the coefficient of the exponential term changes the sign around Lifshitz transition.…
Motivated by the spin-triplet superconductor Sr2RuO4, the thermal Hall conductivity is investigated for several pairing symmetries with broken time-reversal symmetry. In the chiral p-wave phase with a fully opened quasiparticle excitation gap, the temperature dependence of the thermal Hall conductivity has a temperature linear term associated with the topological property directly, and an exponential term, which shows a drastic change around the Lifshitz transition. Examining f-wave states as alternative candidates with $\bm d=Δ_0\hat{z}(k_x^2-k_y^2)(k_x\pm ik_y)$ and $\bm d=Δ_0\hat{z}k_xk_y(k…
Low temperature thermal conductivity in a d-wave superconductor with coexisting charge order: Effect of self-consistent disorder and vertex corrections
