本文在Eliashberg理论的框架下对多带超导体的正常态电阻率进行了理论分析。结果与高纯Ba $_{0.68}$ K $_{0.32}$ Fe $_{2}$ As $_{2}$单晶的正常态电阻率随温度变化的测量结果进行了比较，所报道的最高转变温度为$T_c$ = 38.5 K。实验数据表明，从布洛赫-格吕奈森行为，即在高温下的电阻率饱和的趋势，强烈的偏差。在两个频带的情况下，当第一个频带是强耦合和相对干净的，而第二个频带是弱耦合的，其特征在于更强的杂质散射解释所观察到的行为的电阻率。
英文摘要：
We present theoretical analysis of the normal state resistivity in multiband superconductors in the framework of Eliashberg theory. The results are compared with measurements of the temperature dependence of normal state resistivity of high-purity Ba$_{0.68}$K$_{0.32}$Fe$_{2}$As$_{2}$ single crystals with the highest reported transition temperature $T_c$ = 38.5 K. The experimental data demonstrate strong deviations from the Bloch-Grüneisen behavior, namely the tendency to saturation of the resistivity at high temperatures. The observed behavior of the resistivity is explained within the two band scenario when the first band is strongly coupled and relatively clean, while the second band is weakly coupled and is characterized by much stronger impurity scattering.
We report for the first time the occurrence of superconductivity in the quaternary silicide carbide YRe2SiC with Tc = 5.9 K. The emergence of superconductivity was confirmed by means of magnetic susceptibility, electrical resistivity, and heat capacity measurements. The presence of a well developed heat capacity feature at Tc confirms that superconductivity is a bulk phenomenon, while a second feature in the heat capacity near 0.5 Tc combined with the unusual temperature dependence of the upper critical field Hc2(T) indicate the presence of a multiband superconducting state. Additionally, the …
Multiband behavior and non-metallic low-temperature state of K$_{0.50}$Na$_{0.24}$Fe$_{1.52}$Se$_{2}$
我们报道了超导体KPDMATHABMM Na $_{0.24}$ Fe $_{1.52}$ Se $_{2}$与$T_{c}\approx 20$ K的多带输运和绝缘低温正常态的证据。温度依赖的上临界场，$H_{c2}$，很好地描述了一个两带BCS模型。正常状态下的电阻，在低温下，只有在脉冲磁场，显示绝缘对数温度依赖性的$T \rightarrow 0$超导性被抑制后。这与高$T_{c}$铜氧化物和颗粒I型超导体相似，表明在高磁场中观察到的超导体-绝缘体转变与固有的纳米级相分离有关。
We studied the effects of multiband electronic structure on the thermoelectric and electrical transport properties in the normal state of kagome superconductors $A$V$_3$Sb$_5$ ($A$ = K, Rb, Cs). In all three members, the multiband nature is manifested by sign changes in the temperature dependence of the Seebeck and Hall resistivity, together with sublinear response of the isothermal Nernst and Hall effects to external magnetic fields in the charge ordered state. Moreover, ambipolar transport effects appear ubiquitously in all three systems, giving rise to sizable Nernst signal. Finally, possib…
Role of multiband effects and electron-hole asymmetry in the superconductivity and normal state properties of Ba(Fe$_{1-x}$Co$_{x}$)$_{2}$As$_{2}$
本文系统地研究了Ba（Fe $_{1-x}$ Co $_{x}$）$_{2}$ As $_{2}$在宽掺杂范围内的电阻率和霍尔效应。我们发现了一个令人惊讶的巨大差距之间的弛豫率的空穴和电子，超过一个数量级的低掺杂，低温制度。电子与空穴迁移率的比率随着温度和掺杂（远离磁有序状态）而减小，并且变得更加常规。我们还发现了一个简单的解释大的不对称性（相比铜酸盐）的超导圆顶：在欠掺杂制度的决定性因素是AF和超导性（SC）之间的竞争，而在过掺杂制度的主要作用是发挥退化的嵌套，削弱配对相互作用。结果表明，带间电子-空穴散射引起的自旋涨落不仅在超导配对中起着重要作用，而且在正常输运中也起着重要作用。
In this letter, we have examined the superconducting ground state of the HfV$_2$Ga$_4$ compound using resistivity, magnetization, zero-field (ZF) and transverse-field (TF) muon-spin relaxation and rotation ($μ$SR) measurements. Resistivity and magnetization unveil the onset of bulk superconductivity with $T_{\bf c}\sim$ 3.9~K, while TF-$μ$SR measurements show that the temperature dependence of the superfluid density is well described by a nodal two-gap $s$+$d$-wave order parameter model. In addition, ZF muon relaxation rate increases with decreasing temperature below 4.6 K, indicating the pres…
Planar normal state resistivity data taken from three families of cuprate superconductors are compared with theoretical calculations from the recent extremely correlated Fermi liquid theory (ECFL). The two hole doped cuprate materials $LSCO$ and $BSLCO$ and the electron doped material $LCCO$ have yielded rich data sets at several densities $δ$ and temperatures T, thereby enabling a systematic comparison with theory. The recent ECFL resistivity calculations for the highly correlated $t$-$t'$-$J$ model by us give the resistivity for a wide set of model parameters. After using X-ray diffraction a…
We present experimental results for the in-plane resistivity of the electron-doped cuprate superconductor $La_{2-x}Ce_xCuO_4$ above its transition temperature $T_c$ as a function of Ce doping x and temperature. For the doping x between 0.11 and 0.17, where $T_c$ varies from 30 K (x=0.11) to 5 K (x=0.17), we find that the resistivity shows an approximate $T^2$ behavior for all values of doping over the measurement range from 100 K to 400 K. The coefficient of the $T^2$ resistivity term decreases with increasing x following the trend in $T_c$. We analyze our data theoretically and posit that n-t…
Emerging in the 1950s, the multiband superconductivity has been considered for a long time as an approximate model in the form of a generalization of the BCS theory to the case of two bands for a more accurate quantitative description of the properties and characteristics of such superconductors as cuprates, heavy fermions compounds, metal boron carbides, fullerides, strontium ruthenate etc. due to their complex piecewise-continuous Fermi surfaces. However the discovery of the multiband structure of the superconducting state in magnesium diboride in 2001 and iron oxypnictides and chalcogenides…
Correlation between the strength of low-temperature T-linear normal-state resistivity and $T_{\rm c}$ in overdoped electron-doped cuprate superconductors
本文在动能驱动超导框架内，揭示了过掺杂电子掺杂型铜氧化物超导体中由自旋激发同时介导的电子umklapp散射与电子配对，自然导致了低温T线性正常态电阻率强度与超导转变温度$T_{\ m c}$之间的内在关联。
Two-electronic component behavior in the multiband FeSe$_{0.42}$Te$_{0.58}$ superconductor
本文报道了单晶超导FeSe $_{0.42}$ Te $_{0.58}$（$T_c$ = 11.5（1）K）的X波段EPR和$^{125}$ Te和$^{77}$ Se NMR测量结果。这些数据提供了证据的共存的内在本地化和巡回电子状态。在正常状态下，局域磁矩耦合到Fe（Se，Te）层中的巡游电子，并影响局域自旋磁化率和自旋涨落。在$T_c$以下，自旋涨落被迅速抑制，出现了一种非常规的超导状态，其中$1/T_1$以比传统的$s$或$s_\pm$波对称所预期的快得多的速率被还原。我们认为，局域态产生的强电子相关内的Fe衍生带。多带电子结构与电子相关性一起决定了FeSe $_{1-x}$ Te $_x$族的正常态和超导态，它似乎比以前预期的更接近其他高$T_c$超导体。
The resistivity and the Hall effect in the copper-oxide high-temperature superconductor YBa$_{2}$Cu$_{3}$O$_{7-δ}$ (YBCO) are remarkably anisotropic. Using a thin film of YBCO grown on an off-axis cut SrTiO$_3$ substrate allows one to investigate these anisotropic transport properties in a planar and well-defined sample geometry employing a homogeneous current density. In the normal state, the Hall voltage probed parallel to the copper-oxide layers is positive and strongly temperature dependent, whereas the out-of-plane Hall voltage is negative and almost temperature independent. The results c…
We calculate analytically the spectrum of the Andreev bound states in a half-infinite superconducting wire with an arbitrary number of bands crossing the chemical potential. The normal state of the wire is assumed to have an antiunitary symmetry A (time reversal or its combination with a crystallographic point group operation), with A^2=-1 or +1. This symmetry may be broken by the superconducting order parameter and/or the boundary scattering. We present a model-independent proof of the existence of one Majorana mode near the end of the wire with an odd number of bands.
Detailed measurements of the in-plane resistivity were performed in a high-quality Ba(Fe$_{1-x}$Co$_{x}$)$_2$As$_2$ ($x=0.065$) single crystal, in magnetic fields up to 9 T and with different orientations $θ$ relative to the crystal $c$ axis. A significant $ρ(T)_{H,θ}$ rounding is observed just above the superconducting critical temperature $T_c$ due to Cooper pairs created by superconducting fluctuations. These data are analyzed in terms of a generalization of the Aslamazov-Larkin approach, that extends its applicability to high reduced-temperatures and magnetic fields. This method allows us …
Superconducting transition temperature $T_C$ of some of the cubic $β$-phase Mo$_{1-x}$Re$_x$ alloys with x > 0.10 is an order of magnitude higher than that in the elements Mo and Re. We investigate this rather enigmatic issue of the enhanced superconductivity with the help of experimental studies of the temperature dependent electrical resistivity ($ρ$(T)) and heat capacity (C$_P$(T)), as well as the theoretical estimation of electronic density of states (DOS) using band structure calculations. The $ρ$(T) in the normal state of the Mo$_{1-x}$Re$_x$ alloys with x > 0.15 is distinctly different …
A method is proposed to extend the zero-temperature Hall-Klemm microscopic theory of the Knight shift $K$ in an anisotropic and correlated, multi-band metal to calculate $K(T)$ at finite temperatures $T$ both above and into its superconducting state. The transverse part of the magnetic induction ${\bf B}(t)={\bf B}_0+{\bf B}_1(t)$ causes adiabatic changes suitable for treatment with the Keldysh contour formalism and analytic continuation onto the real axis. We propose that the Keldysh-modified version of the Gor'kov method can be used to evaluate $K(T)$ at high ${\bf B}_0$ both in the normal s…
Resistivity saturation in PrFeAsO$_{1-x}$F$_y$ superconductor: An evidence of strong electron-phonon coupling
我们测量了PrFeAsO $_{1-x}$ F $_y$样品在很宽的温度范围内的电阻率，以阐明电子-声子相互作用对正常和超导态性质的作用。$ρ$在170 K以上的线性T依赖性，随后在更高温度下的饱和行为是强电子-声子耦合的明显特征。通过对$ρ$的T依赖性的分析，我们估计了几个正常态参数，这些参数对理解该系统的超导电性起源是有用的。我们的研究结果表明，铁基氧磷属化合物是声子介导的BCS超导体，像Chevrel相和A15化合物。
The aim of this work is to investigate the temperature dependencies both in CuO2-plane and out-of plane resistivities in electron-doped Nd2-xCexCuO4 for x from 0.135 up to 0.15 in order to analyze the anisotropy of the electrical transport in the process of the evolution from antiferromagnetic (AF) order in underdoped region to superconducting (SC) order in optimally doped region.
Suppression of superconductivity in layered Bi4O4S3 by Ag doping
本文报道了新型层状超导体Bi_（4-x）Ag_xO_（4-S）_3（0<x<0.2）多晶样品的X射线衍射、磁化强度和输运测量结果。当x>0.10时，超导转变温度（TC）逐渐降低，最后被抑制.因此，电阻率从x 0.1的金属行为改变<0.1 to a semiconductor-like behavior for x>。Seebeck系数的分析表明，有两种类型的类电子载流子占主导地位，在不同的温度范围内，表示负责的输运性质的多带效应。超导性的抑制和电阻率的增加可以归因于掺杂后费米能级向低能侧的偏移，这降低了EF处的态密度。此外，我们的结果表明，在母Bi 4 O 4S 3的超导电性是本征和掺杂剂Ag更喜欢进入BiS 2层，这可能会从根本上改变电子结构。
Impurity-Scattering Assisted Umklapp Scattering as the Origin of Low-Temperature Resistivity in the Normal-State of Cuprate Superconductors
Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所）；College of Physics, Chongqing University（重庆大学物理学院）；School of Physics, Beihang University（北京航空航天大学物理学院）；School of Physics and Astronomy, Beijing Normal University（北京师范大学物理与天文学院）；Department of Physics, Beijing Normal University, Zhuhai（北京师范大学珠海校区物理系）
