Uncovering novel states of quantum matter in strongly correlated spin systems under extreme conditions

• Grant number: 19/24711-0
• Support type: Scholarships in Brazil - Doctorate (Direct)
• Effective date (Start): March 01, 2020
• Effective date (End): September 30, 2023
• Field of knowledge: Physical Sciences and Mathematics - Physics - Condensed Matter Physics
• Principal researcher: Julio Antonio Larrea Jimenez
• Grantee: Fernando de Almeida Passos
• Home Institution: Instituto de Física (IF). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 18/08845-3 - An investigation into topological and exotic quantum states under extreme conditions (InvestInTopQuantEx), AP.JP

Abstract

The thesis project of the PhD candidate, Fernando de Almeida Passos (hereafter called as DD2 candidate) is going to deal with a current puzzle in condensed matter physics: to understand the physical mechanisms that account for an entanglement of spin degrees of freedom and novel states of matter close to a Quantum Phase Transition (QPT). In order to reach our goals, we propose to investigate two selected strongly correlated spin systems under different tuning control parameters: the application of high pressure, magnetic field, chemical substitution and reduction of the system's finite size.This proposal is rather innovative and will challenge the DD2 candidate to overcome several issues which involve from the synthesis of new alloy nanoparticles with state-of-the-art sample preparation until the set of new "home-built" experimental methods to measure physical properties under extreme conditions of very low temperatures, intense magnetic field and high-pressure. Remarkably, such new experimental methods under extreme conditions to be set in the Institute of Physics, University of São Paulo (IF USP), are still not available in commercial setups. On the other hand, the investigation of novel states of quantum matter is covered by tuning the spin and electron correlation in the quantum paramagnet SrCu$_2$(BO$_3$)$_2$ (SCBO) and the permanent magnet Sm$_{1-x}$Y$_x$Co$_5$ (SYC). While for SCBO the phase diagram will be uncovered by physical property measurement under extreme conditions: very high pressure (up to 250 kbar), very low temperature (down to 0.05 K) and intensive magnetic field (up to 17 T), for SYC the phase diagram will be uncovered at ambient pressure ($p=0$) and at temperatures higher than room temperature. In order to investigate the evolution of magnetism in SYC, the material will be synthesized at the nanoscopic scale. Our aim is to get a better understanding how correlations between different degrees of freedom might form novel magnetic states, both with trivial and nontrivial topology. We expect that the results of this PhD thesis boost the DD2 candidate to be an outstanding Doctor in Physics with hard skills on sample preparation, development of experimental methods beyond the state-of-the-art and problem solver of hot issues at the frontier of Science. The achievements also will benefit the Young Investigator FAPESP project InvestInTopQuantEx (Process 2018/08845-3), contributing to reveal novel states of quantum matter and to pave an alternative route to reach new generation of functional quantum materials with promising application in hard magnets, superconductivity and quantum computing. (AU)