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Global phase diagram of a spin-orbital Kondo impurity model and the suppression of Fermi-liquid scale

Yilin Wang, Brookhaven National Lab, Upton, New York
Tue, 2019-12-31 13:30 - 14:30
TDLI Meeting Room 200 (East Wing of Pao Yue-kong Library)

Many correlated metallic materials are described by Landau Fermi-liquid theory at low energies, but for Hund metals the Fermi-liquid coherence scale TFL is found to be surprisingly small. In this Letter, we study the simplest impurity model relevant for Hund metals, the three-channel spin-orbital Kondo model, using the numerical renormalization group (NRG) method and compute its global phase diagram. In this framework, TFL becomes arbitrarily small close to two new quantum critical points (QCPs) which we identify by tuning the spin or spin-orbital Kondo couplings into the ferromagnetic regimes. We find quantum phase transitions to a singular Fermi-liquid or a novel non-Fermi-liquid phase. The new non-Fermi-liquid phase shows frustrated behavior involving alternating overscreenings in spin and orbital sectors, with universal power laws in the spin (?‰??’1/5), orbital (?‰1/5) and spin-orbital (?‰1) dynamical susceptibilities. These power laws, and the NRG eigenlevel spectra, can be fully understood using conformal field theory arguments, which also clarify the nature of the non-Fermi-liquid phase.

Biography:

Dr. Yilin Wang is a theoretical physicist, working in the field of computational condensed matter physics. His research interests include first-principle calculations of strongly correlated materials using density functional theory plus dynamical mean-field theory (DFT+DMFT) or plus Gutzwiller method (DFT+Gutzwiller), and also theoretically simulations of  resonant inelastic x-ray scattering (RIXS) spectra based on exact diagonalization (ED) method. He also develops numerical codes such as iQIST package (https://github.com/iqist/iqist) implementing continuous-time quantum Monte Carlo (CTQMC) method  and EDRIXS package (https://github.com/NSLS-II/edrixs) for RIXS simulations. Recently, he focuses on studying the multi-orbital metallic systems (Hund metals) where the correlations derive from the Hund’s couplings. He received his Ph.D in condensed matter physics from the Institute of Physics, Chinese Academy of Science in 2016. He is now working as a postdoc with Prof. Gabriel Kotliar in the center for computational materials, spectroscopy and design of Brookhaven National Laboratory, New York, USA. He was supported by the US Department of energy, Office of Science, Basic Energy Sciences as a part of the Computational Materials Science Program through the Center for Computational Design of Functional Strongly Correlated Materials and Theoretical Spectroscopy.

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