9/13：Seminar Information　Professor Naurang L. Saini (Sapienza University of Rome)

　N. L. Saini先生のセミナーを開催します。滞在日程の都合により土曜日の開催になっておりますが、興味のある方のご参加をお待ちしております。

題目 ： Local disorder, atomic fluctuations and electronic structure of some inhomogeneous superconductors
講師 ： Professor Naurang L. Saini (Sapienza University of Rome)
日時 ： 9月13日(土)　14:00-15:00
会場 ： 基礎研セミナー室 (基礎研棟3F)


Dear Colleagues,

We will hold a seminar by Professor N. L. Saini, who will visit RIIS from 9/13-9/15. Due to the schedule of his stay, the event will be held on Saturday, but we look forward to your participation if you are interested.

Title: Local disorder, atomic fluctuations and electronic structure of some inhomogeneous superconductors
Speaker: Professor Naurang L. Saini (Sapienza University of Rome)
Date and time: September 13th (Saturday), 14:00-15:00
Place: Seminar room (RIIS building 3F)

Abstract:
It is now gaining recognition that local disorder in emerging materials plays a crucial role in determining their functional properties, such as superconductivity, magnetism, and electronic transport. In particular, spin charge and lattice fluctuations drive the materials to form fragmented nanoscale structures in which competing short-range and long-range interactions prevail in defining the transport properties. In such cases, experimental tools sensitive to the local structure and dynamics are essential for investigating underlying interactions and their implications. Here, some recent studies on disordered and inhomogeneous superconductors will be discussed. These studies employ space-resolved techniques in conjunction with physical and statistical tools. Scanning X-ray micro-fluorescence is used to visualize the morphology of the chemical phase separation coupled with the percolation in a model granular iron-based superconductor. The results will be further substantiated by coherent diffraction and X-ray photon correlation spectroscopy. Scanning photoemission microscopy and angle-resolved photoemission spectroscopy are employed to study high-entropy alloy (HEA) type REOBiS2 layered superconductors. Soft X-ray absorption (XAS) and X-ray photoemission spectroscopy (XPS) measurements are also conducted to reveal the differing electronic properties of equivalent and non-equivalent RE mixing as a function of mixing entropy. The results provide clear evidence of Ce3+/Ce4+ mixed valence in the HEA-type REOBiS2, similar to the pristine CeOBiS2 compound. This suggests a similar charge transfer mechanism responsible for self-doping in these materials. The distinct behaviors observed in equivalent and non-equivalent mixing are attributed to differing potential energy landscapes of the Bi sites, where intrinsic disorder is expected to exhibit distinct characteristics of superconductivity. Finally, space-resolved spectroscopic results will be presented on transition metal dichalcogenides, including heavily interlaced Cu0.33TiSe2, demonstrating the √3 × √3 CDW phase and related systems.