Pressure-induced and Composition-induced Structural Quantum Phase Transition in the Cubic Superconductor (Sr/Ca)_3Ir_4Sn_{13}

Non-cubic layered structure of Ba(1-x)K(x)BiO3 superconductor

Bismuthate superconductor Ba(1-x)K(x)BiO3 (x=0.27-0.49, Tc=25-32K) grown by an electrolysis technique was studied by electron diffraction and high-resolution electron microscopy. The crystalline structure thereof has been found to be non-cubic, of the layered nature, and non-centrosymmetric, with the lattice parameters a ~ ap, c ~ 2ap (ap is a simple cubic perovskite cell parameter) containing an ordered arrangement of barium and potassium. The evidence for the layered nature of the bismuthate superconductor removes the principal crystallographic contradiction between bismuthate and cuprate hi…

Unconventional charge-density wave in Sr3Ir4Sn13 cubic superconductor revealed by optical spectroscopy study

Sr3Ir4Sn13 is an interesting compound showing a coexistence of structural phase transition and superconductivity. The structural phase transition at 147 K leads to the formation of a superlattice. We performed optical spectroscopy measurements across the structural phase transition on single crystal sample of Sr3Ir4Sn13. The optical spectroscopy study reveals an unusual temperature induced spectral weight transfer over broad energy scale, yielding evidence for the presence of electron correlation effect. Below the structural phase transition temperature an energy gap-like suppression in optica…

立方La3Al中的间隙阴离子电子超导电性

Superconductivity in cubic La3Al with interstitial anionic electrons

本研究报道立方La3Al单晶在Tc~6.32 K下进入超导态，为体块II型BCS超导体，理论计算揭示其间隙阴离子电子位于晶胞体心，证实电子-声子耦合机制，属新型电化物超导体。

Superlight pairs in face-centred-cubic extended Hubbard models with strong Coulomb repulsion

The majority of fulleride superconductors with unusually high transition-temperature to kinetic-energy ratios have a face-centred-cubic (FCC) structure. We demonstrate that, within extended Hubbard models with strong Coulomb repulsion, paired fermions in FCC lattices have qualitatively different properties than pairs in other three-dimensional cubic lattices. Our results show that strongly bound, light, and small pairs can be generated in FCC lattices across a wide range of the parameter space. We estimate that such pairs can Bose condense at high temperatures even if the lattice constant is l…

Incommensurate spin-density wave order in electron-doped BaFe2As2 superconductors

Neutron diffraction studies of Ba(Fe[1-x]Co[x])2As2 reveal that commensurate antiferromagnetic order gives way to incommensurate magnetic order for Co compositions between 0.056 < x < 0.06. The incommensurability has the form of a small transverse splitting (0, +-e, 0) from the nominal commensurate antiferromagnetic propagation vector Q[AFM] = (1, 0, 1) (in orthorhombic notation) where e = 0.02-0.03 and is composition dependent. The results are consistent with the formation of a spin-density wave driven by Fermi surface nesting of electron and hole pockets and confirm the itinerant nature of m…

掌型立方砧压力室中的软点接触安德烈夫反射光谱学

Soft point-contact Andreev reflection spectroscopy in a palm-type cubic anvil-pressure cell

研究在掌型立方砧压力室中实现软点接触安德烈夫反射光谱，结合两种技术可在高压下稳定形成点接触结，对Nb等材料测量，观察到零偏置电导峰并研究其相关特性，为非常规超导性提供证据，搭建实验平台开辟研究新途径。