Polycrystalline La$_{7}$Ir$_{3}$ is reported to show superconductivity breaking time-reversal symmetry while also having an isotropic $s$-wave gap. Single crystals of this noncentrosymmetric superconductor are highly desirable to understand the nature of the electron pairing mechanism in this system. Here we report the growth of high-quality single crystals of La$_{7}$Ir$_{3}$ by the Czochralski method. The structural and superconducting properties of these large crystals have been investigated using x-rays, magnetization, resistivity and heat capacity measurements. We observe a clear anisotropy in the lower and upper critical fields for magnetic fields applied parallel and perpendicular to the hexagonal $c$ axis. We also report the presence of a robust electronic critical field, that diverges from the upper critical field derived from heat capacity, which is the hallmark of surface superconductivity.
Weakly anisotropic superconductivity of Pr4Ni3O10 single crystals
ShanghaiTech University（上海科技大学）；Center for High Pressure Science and Technology Advanced Research（高压科学与技术先进研究中心）；Institute for Shanghai Advanced Research in Physical Sciences (SHARPS)（上海物理科学研究院）；Songshan Lake Materials Laboratory（松山湖材料实验室）；Qufu Normal University（曲阜师范大学）；University of Oxford（牛津大学）；Southeast University（东南大学）；Tsinghua University（清华大学）
The recently discovered kagome superconductor CsV$_3$Sb$_5$ ($T_c \simeq 2.5$ K) has been found to host charge order as well as a non-trivial band topology, encompassing multiple Dirac points and probable surface states. Such a complex and phenomenologically rich system is, therefore, an ideal playground for observing unusual electronic phases. Here, we report on microscopic studies of its anisotropic superconducting properties by means of transverse-field muon spin rotation ($μ$SR) experiments. The temperature dependences of the in-plane and out-of-plane components of the magnetic penetration…
The superconductors with the Ginzburg-Landau (G-L) parameter ($κ$) $\sim1/\sqrt{2}$ exist near a critical Bogolomonyi (B) point where they show inter-type domains between type-I and type-II superconductivity. While such physics is well understood for isotropic superconductors, the experimental investigation of the physics of anisotropic superconductors near a critical B-point remains an unattained goal mainly due to the unavailability of model material systems. Theoretically, such superconductors are expected to show type-I or type-II behaviour for definite directions of an applied magnetic fi…
We use the spin-fermion model to describe the CuO$_2$ planes of the high-Tc superconductors. Using a large wavelength approach, we show that the ferromagnetic component of the Cu spin fluctuations couple to the oxygen holes producing a pairing interaction that leads to a superconducting gap whose symmetry is determined by the anisotropy of the Kondo interaction. We calculate Tc as a function of the hole concentration in a mean-field approximation and our numerical results are in good agreement with the experiments.
We investigate low-temperature electronic properties of the nondimeric organic superconductor $β^{\prime\prime}$-(BEDT-TTF)$_4$[(H$_3$O)Ga(C$_2$O$_4$)$_3$]PhNO$_2$. By examining ultrasonic properties, charge disproportionation (CD) without magnetic field dependence is detected below $T_{\rm CD}$$\sim$8~K just above the superconducting critical temperature $T_{\rm c}$$\sim$6~K. From quantum oscillations in high fields, we find variation in the Fermi surface and mass enhancement induced by the CD. Heat capacity studies elucidate that the superconducting gap function is fully gapped in the Fermi …
Anisotropic inelastic scattering and its interplay with superconductivity in URu$_{2}$Si$_{2}$
与几乎所有的各向异性超导体相反，URu $_{2}$ Si $_{2}$的上临界场当场沿低导电方向取向时较大。我们提出了一个研究的电阻率和塞贝克系数延伸到亚开尔文温度范围内揭示了一个奇异的情况下的各向异性。当电流沿c轴方向注入时，$_{2}$ Si $_{2}$表现为低密度费米液体。当它沿着a轴流动时，即使在存在大的场的情况下，电阻率仍保持T线性下降到T $_{c}$，并且塞贝克系数在非常低的温度下经历符号变化。我们的结论是，特征能量尺度是各向异性的和消失的小基面。
The 12442 compounds are a recently discovered family of iron-based superconductors, that share several features with the cuprates due to their strongly anisotropic structure, but are so far poorly understood. Here, we report on the gap structure and anisotropy of RbCa2(Fe1-xNix)4As4F2 single crystals, investigated by a combination of directional point-contact Andreev-reflection spectroscopy and coplanar waveguide resonator measurements. Two gaps were identified, with clear signatures of d-wave-like nodal structures which persist upon Ni doping, well described by a two-band d-d state with symme…
Anisotropic $H_{c2}$ determined up to 92 T and the signature of multi-band superconductivity in Ca$_{10}$(Pt$_{4}$As$_{8}$)((Fe$_{1-x}$Pt$_{x}$)$_{2}$As$_{2}$)$_{5}$ superconductor
Anisotropic Superconductivity with Enhanced Critical Field in Strained RuO2
The Ohio State University（俄亥俄州立大学）；Cornell University（康奈尔大学）；Williams College（威廉姆斯学院）；Kavli Institute at Cornell for Nanoscale Science, Cornell University（康奈尔大学卡弗里纳米科学研究所）；Leibniz-Institut für Kristallzüchtung（莱布尼茨晶体生长研究所）
Gigantic anisotropic uniaxial pressure effect on superconductivity within the CuO2 plane of La1.64Eu0.2Sr0.16CuO4 - strain control of stripe criticality
Anisotropic strain is an external field capable of selectively addressing the role of nematic fluctuations in promoting superconductivity. We demonstrate this using polarization-resolved elasto-Raman scattering to probe the evolution of nematic fluctuations under strain in the normal and superconducting states of the paradigmatic iron-based superconductor Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$. In the non-superconducting parent compound BaFe$_2$As$_2$ we observe a strain-induced suppression of the nematic susceptibility which follows the expected behavior of an Ising order parameter under a symmetry b…
The iron-based superconductors are an ideal platform to reveal the enigma of the unconventional superconductivity and potential topological superconductivity. Among them, the monolayer Fe(Se,Te)/SrTiO3(001), which is proposed to be topological nontrivial, shows interface-enhanced high-temperature superconductivity in the two dimensional limit. However, the experimental studies on the superconducting pairing mechanism of monolayer Fe(Se,Te) films are still limited. Here, by measuring quasiparticle interference in monolayer Fe(Se,Te)/SrTiO3(001), we report the observation of the anisotropic stru…
Proximity effect facilitates the penetration of Cooper pairs that permits superconductivity in normal metal, offerring a promising approach to turn heterogeneous materials into superconducting and develop exceptional quantum phenomena. Here, we have systematically investigated proximity-induced anisotropic superconductivity in monolayer Ni-Pb binary alloy by combining scanning tunneling microscopy/ spectroscopy(STM/STS) with theoretical calculations. By means of high temperature growth, the(3root3by3root3)R30o Ni-Pb surface alloy has been fabricated on the Pb(111), where the appearance of doma…
Materials with exceptional magnetism and superconductivity usually conceive emergent physical phenomena. Here, we investigate the physical properties of the (Eu,La)FeAs2 system with double magnetic sublattices. The parent EuFeAs2 shows anisotropy-associated magnetic behaviors, such as Eu-related moment canting and exchange bias. Through La doping, the magnetic anisotropy is enhanced with ferromagnetism of Eu2+ realized in the overdoped region, and a special exchange bias of the superposed ferromagnetic/superconducting loop revealed in Eu0.8La0.2FeAs2. Meanwhile, the Fe-related antiferromagneti…
Two-gap superconductivity in single crystal Lu$_2$Fe$_3$Si$_5$ from penetration depth measurements
用隧道二极管共振技术研究了Lu $_2$ Fe $_3$ Si $_5$单晶的迈斯纳态和混合态。超流密度的温度依赖性提供了强有力的证据，两个间隙的超导性几乎相等的贡献，从每个间隙的大小$Δ_1/k_BT_c=1.86$和$Δ_1/k_BT_c=0.54$。在涡旋态，钉扎强度表现出异常强的温度依赖性，并与磁场（峰值效应）是非单调的。不可逆性线是明确的，是相当遥远的$H_{c2}(T)$，这暗示在这个双间隙系统中的增强涡波动。总之，我们的研究结果提供了强有力的电磁测量支持Lu $_2$ Fe $_3$ Si $_5$中的双能隙超导先前建议从比热测量。
