Single crystals of RbOs2O6 have been grown from Rb2O and Os in sealed quartz ampoules. The crystal structure has been identified at room temperature as cubic with the lattice constant a = 10.1242(12) A. The anisotropy of the tetrahedral and octahedral networks is lower and the displacement parameters of alkali metal atoms are smaller than for KOs2O6, so the "rattling" of the alkali atoms in RbOs2O6 is less pronounced. Superconducting properties of RbOs2O6 in the mixed state have been well described within the London approach and the Ginzburg-Landau parameter kappa(0) = 31 has been derived from the reversible magnetization. This parameter is field dependent and changes at low temperatures from kappa = 22 (low fields) to kappa = 31 at H_{c2}. The thermodynamic critical field H_{c}(0) = 1.3 kOe and the superconducting gap 2delta/k_{B}T_{c} = 3.2 have been estimated. These results together with slightly different H_{c2}(T) dependence obtained for crystals and polycrystalline RbOs2O6 proof evidently that this compound is a weak-coupling BCS-type superconductor close to the dirty limit.
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Inelastic X-ray Scattering Study of superconducting SmFeAs(O$_{1-x}$F$_{y}$) Single Crystals: Evidence for Strong Momentum-Dependent Doping-Induced Renormalizations of Optical Phonons
本文报道了SmFeAsO和超导SmFeAsO $_{0.6}$ F $_{0.35}$单晶晶格动力学的非弹性X射线散射实验。特别注意的是沿[100]方向的三个光学模式接近23 meV，偏振的FeAs平面的色散。值得注意的是，这些模式中的两个强烈重整化氟掺杂。这些结果提供了显着的洞察的能量和动量的依赖性的晶格的耦合到电子系统，并强调自旋-声子耦合的重要性，在超导铁磷属元素化物。
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$T_c$ .
Single crystals of the unconventional superconductor UTe$_2$ have been grown in various conditions which result in different superconducting transition temperature as well as normal state properties. Stoichiometry of the samples has been characterized by the single-crystal X-ray crystallography and electron microprobe analyses. Superconducting samples are nearly stoichiometric within an experimental error of about 1 \%, while non-superconducting sample significantly deviates from the ideal composition. The superconducting UTe$_2$ showed that the large density of states was partially gapped in …
We have combined elastic and inelastic neutron scattering techniques, magnetic susceptibility and resistivity measurements to study single-crystal samples of K$_x$Fe$_{2-y}$Se$_2$, which contain the superconducting phase that has a transition temperature of $\sim$31 K. In the inelastic neutron scattering measurements, we observe both the spin-wave excitations resulting from the block antiferromagnetic ordered phase and the resonance that is associated with the superconductivity in the superconducting phase, demonstrating the coexistence of these two orders. From the temperature dependence of t…
Thermal conductivity of overdoped BaFe$_{1.73}$Co$_{0.27}$As$_2$ single crystal: Evidence for nodeless multiple superconducting gaps and interband interactions
测量了过掺杂的FeAs基超导体BaFe $_{1.73}$ Co $_{0.27}$ As $_2$（$T_c$ = 8.1 K）单晶的面内热导率$κ$，其热导率低至80 mK。在零磁场下，剩余的线性项$κ_0/T$可以忽略不计，表明在$ab$平面上存在无结超导能隙.在磁场中，$κ_0/T$迅速增加，与传统的s波超导体有很大不同。这种反常的$κ_0/T(H)$可能揭示了在过掺杂BaFe $_{1.73}$ Co $_{0.27}$ As $_2$中的一种奇异的超导能隙结构：消失空穴（$β$）的能隙比包含大部分载流子的电子（$γ$和$δ$）的能隙大得多。这种奇异的带隙结构是由带间相互作用诱导的超导态的证据，其中具有{ \it较小}态密度的带具有{ \it较大}带隙。
Recent experiments have pointed to a chiral p-wave-like superconductivity in epitaxial Bi/Ni bilayers that are spontaneously time-reversal symmetry breaking (TRSB), making it a promising platform for exploring physics useful for topologically protected quantum computing. Quite intriguingly, evidence has emerged that in non-epitaxial Bi/Ni bilayers, superconductivity arises due to the formation of NiBi3, which has been reported to host coexisting ferromagnetic and superconducting orders at the surface. We perform high resolution surface magneto-optic Kerr effect (SMOKE) measurements using a Sag…
Measurement of a Sign-Changing Two-Gap Superconducting Phase in Electron-Doped Ba(Fe_{1-x}Co_x)_2As_2 Single Crystals using Scanning Tunneling Spectroscopy
Superconducting Sm(O,F)BiS2 single crystals were successfully grown using KI-KCl flux. The obtained single crystals were flat-shaped and their size was 500um. The structure and composition of the obtained single crystals were obtained using X-ray diffraction and X-ray spectroscopy. The lattice constants of the obtained Sm(O,F)BiS2 single crystals were evaluated to be a = 3.9672(4) A and c = 13.417(6) A, while their F/(O + F) molar ratio was approximately 0.17. The superconducting transition temperature of the obtained Sm(O,F)BiS2 single crystals was 4.8 K. This was different from the reported …
Cd-doped La(O,F)BiS2 single crystals were grown using a CsCl/KCl flux. The grown crystals have a plate-like shape with ~1-2 mm square size in a well-developed ab-plane. The Cd doping in the crystals was successfully characterized by single crystal X-ray diffraction and electron probe microanalysis techniques. The superconductivity of La(O,F)BiS2 was gradually suppressed with Cd doping. The superconducting transition temperature with zero resistivity of La(O0.54F0.46)(Bi0.92Cd0.08)S2 was 2.3 K. The Cd doping does not change the superconducting anisotropy so much, albeit the considerable suppres…
We use spatially-resolved transport techniques to investigate the superconducting properties of single crystals La$_{2-x}$Ba$_x$CuO$_4$. We find a new superconducting transition temperature $T_{cs}$ associated with the ab-plane surface region which is considerably higher than the bulk $T_c$. The effect is pronounced in the region of charge carrier doping $x$ with strong spin-charge stripe correlations, reaching $T_{cs}=36$ K or 1.64$T_c$.
NbBiCh$_3$ (Ch = S, Se) misfit-layered superconducting single crystals were successfully grown using a CsCl/KCl flux for the first time. The obtained crystals had a well-developed habit parallel to the c-plane with a typical width of 1-2 mm and thickness of 10-40 um. The superconducting transition temperatures with zero resistivity of NbBiS$_3$ single crystals obtained from the nominal composition of Nb0.9Bi1.2S3 was 0.31 K, and that value of the NbBiSe$_3$ single crystals grown from the stoichiometry composition (NbBiSe$_3$) was 2.3 K. Sharp decreases in electric resistivity and magnetic susc…
Sm(O,F)BiS2 superconducting single crystals with various nominal F contents have been grown using KI-KCl flux. The solid solution limit of F at the O-site in Sm(O,F)BiS2 single crystals was approximately less than 20 at%. F concentrations of Sm(O,F)BiS2 single crystals were hardly controlled by nominal F contents. It suggests the existence of intrinsic stable phase. Superconductivity was shown at around 5 K. Superconducting transition temperature with zero resistivity were increased with increasing nominal F contents within less than 70 at% in O-site, despite similar F concentration and c-axis…
Observation of anisotropic diamagnetism above the superconducting transition in iron-pnictide Ba_(1-x)K_xFe2As2 single crystals due to thermodynamic fluctuations
