Disentangling Electronic excitations in Hund Metals

• Grant number: 24/13291-8
• Support Opportunities: Regular Research Grants
• Start date: December 01, 2024
• End date: November 30, 2027
• Field of knowledge: Physical Sciences and Mathematics - Physics - Condensed Matter Physics
• Principal Investigator: Fernando Assis Garcia
• Grantee: Fernando Assis Garcia
• Host Institution: Instituto de Física (IF). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated researchers: Abner de Siervo ; Eduardo Matzenbacher Bittar ; Walber Hugo de Brito
• Associated scholarship(s): 25/05379-5 - Synthesis and characterization of ternary Y-Fe-Ge single crystals., BP.MS; 25/06845-0 - X-ray Absorption Spectroscopy of Fe-based Superconductors, BP.IC; 25/03823-5 - Resonant Inelastic X-ray Scattering of Iron-based Superconductors, BP.IC

Abstract

Inspired by the phase diagram of the cuprate oxide family of high temperature superconductors, the focus of our research in recent years has been unconventional superconductivity exhibited by correlated metals. In particular, we devoted attention to the investigation of the Fe-based superconductors (FeSCs), materials for which the formation of the high-temperature superconducting state (HTSC) occurs in proximity, or in coexistence, with other electronic orders. This diversity of electronic phases in the FeSCs phase diagram is evidence of the role played by the coupling between the electronic degrees of freedom (charge, orbital and spin) and the proximity of the energy scales associated with these couplings. These facts have advanced studies on Hund metals, a new class of correlated metals, where itinerant electronic states retain strong orbital character. It is therefore suggested that the central task for understanding the formation of HTSC in Hund metals is to disentangle the role of charge, orbital and spin degrees of freedom in these materials. In this project, we propose to investigate this topic through advanced X-ray spectroscopy and thus contribute to a better understanding of Hund's metals and their relationship with HTSC. Experimental techniques considered include resonant inelastic X-ray scattering (RIXS), angle-resolved photoemission spectroscopy (ARPES), and X-ray absorption spectroscopy (XAS), in particular X-ray linear dichroism (XLD). Materials to be explored include FeSCs, such as i) the 122 AFe2As2 (A= K, Rb, Cs); ii) BaFe2S3 and iii) other Hund metals that exhibit electronic orders such as HTSC, charge and spin density waves and even an electronic nematic order. (AU)