Superconducting Fluctuations in Overdoped Bi2Sr2CaCu2O8 + δ

Fluctuating superconductivity—vestigial Cooper pairing in the resistive state of a material—is usually associated with low dimensionality, strong disorder, or low carrier density. Here, we report single-particle spectroscopic, thermodynamic and magnetic evidence for persistent superconducting fluctuations in the heavily hole-doped cuprate superconductor Bi2Sr2CaCu2O8þδ(Tc¼66 K) despite the high carrier density. With a sign-problem-free quantum Monte Carlo calculation, we show how a partially flat band at ðπ;0Þcan help enhance superconducting phase fluctuations. Finally, we discuss the implications of an anisotropic band structure on the phase-coherence-limited superconductivity in overdoped cuprates and other superconductors

Superconducting fluctuations in overdoped Bi2_2Sr2_2CaCu2_2O8+δ_{8+\delta}

Fluctuating superconductivity - vestigial Cooper pairing in the resistive state of a material - is usually associated with low dimensionality, strong disorder or low carrier density. Here, we report single particle spectroscopic, thermodynamic and magnetic evidence for persistent superconducting fluctuations in heavily hole-doped cuprate superconductor Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ ($T_c$ = 66~K) despite the high carrier density. With a sign-problem free quantum Monte Carlo calculation, we show how a partially flat band at ($\pi$,0) can help enhance superconducting phase fluctuations. Finally, we discuss the implications of an anisotropic band structure on the phase-coherence-limited superconductivity in overdoped cuprates and other superconductors.Comment: main: 8 pages, 6 figures + supplement: 10 pages, 15 figure

Development of laser-combined scanning multiprobe spectroscopy and application to analysis of WSe2/MoSe2 in-plane heterostructure

By combining scanning multiprobe (MP) microscopy with optical methods such as light-modulated spectroscopy (LMS) and optical pump-probe (OPP) method, we have succeeded in developing a microscopy method for measuring electronic structures and photoinduced carrier dynamics in microscopic structures. We demonstrated its performance by analyzing the electronic structures in a monolayer island of a WSe2/MoSe2 in-plane heterostructure grown on a SiO2/Si substrate. By observing the field-effect transistor characteristics and photocurrent mapping over the heterostructure by LMS, we were able to visualize the band structure. Positional dependence of carrier dynamics was also successfully probed by OPP-MP spectroscopy

Synthesis of zirconolite-2M ceramics for immobilisation of neptunium

Praseodymium-doped zirconolite ceramics targeting nominal composition Ca1-xPrxZrTi2-5x/3Al5x/3O7 (x ≤ 0.20, Δx = 0.05) were fabricated by a mixed oxide solid state reaction, at 1350 °C in air for 20 h. Praseodymium (Pr) was employed as a surrogate for neptunium (Np), with Al3+ co-accommodated to provide charge balance. High-resolution transmission electron microscopy and electron diffraction analyses confirmed that zirconolite crystallised as the 2 M monoclinic polytype throughout the phase evolution, with no evidence of transformation to other polytype structures. Phase assemblage and microstructural data were consistent with zirconolite occupying a high fraction of the phase assemblage (>ca. 93 wt %), alongside a minor secondary perovskite phase at all levels of targeted Pr incorporation. Despite this, it was demonstrated near theoretical density formed through a solid-state fabrication route, and we therefore propose that, through analogy with the corresponding Pr solid solution, zirconolite may be a suitable candidate for the immobilisation of Np-bearing wastes