scholarly journals Exceptional band touching for strongly correlated systems in equilibrium

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Tsuneya Yoshida ◽  
Robert Peters ◽  
Norio Kawakami ◽  
Yasuhiro Hatsugai
Keyword(s):  
Green's Functions ◽  
Green’S Functions ◽  
Strongly Correlated Systems ◽  
Strongly Correlated ◽  
Many Body ◽  
Band Structures ◽  
Correlated Systems ◽  
Concise Review ◽  
Open Questions ◽  
Many Body Systems

Abstract Quasi-particles described by Green‘s functions of equilibrium systems exhibit non-Hermitian topological phenomena because of their finite lifetime. This non-Hermitian perspective on equilibrium systems provides new insights into correlated systems and attracts much interest because of its potential to solve open questions in correlated compounds. We provide a concise review of the non-Hermitian topological band structures for quantum many-body systems in equilibrium, as well as their classification.

AN INTRODUCTORY GUIDE TO GREEN’S FUNCTION METHODS IN NUCLEAR MANY-BODY PROBLEMS

1994 ◽  
Vol 03 (02) ◽  
pp. 523-589 ◽  
Author(s):  
T.T.S. KUO ◽  
YIHARN TZENG
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Green's Functions ◽  
Green’S Functions ◽  
Model Space ◽  
Many Body ◽  
Diagram Expansion ◽  
Nucleus Scattering ◽  
Many Body Systems ◽  
General Method

We present an elementary and fairly detailed review of several Green’s function methods for treating nuclear and other many-body systems. We first treat the single-particle Green’s function, by way of which some details concerning linked diagram expansion, rules for evaluating Green’s function diagrams and solution of the Dyson’s integral equation for Green’s function are exhibited. The particle-particle hole-hole (pphh) Green’s function is then considered, and a specific time-blocking technique is discussed. This technique enables us to have a one-frequency Dyson’s equation for the pphh and similarly for other Green’s functions, thus considerably facilitating their calculation. A third type of Green’s function considered is the particle-hole Green’s function. RPA and high order RPA are treated, along with examples for setting up particle-hole RPA equations. A general method for deriving a model-space Dyson’s equation for Green’s functions is discussed. We also discuss a method for determining the normalization of Green’s function transition amplitudes based on its vertex function. Some applications of Green’s function methods to nuclear structure and recent deep inelastic lepton-nucleus scattering are addressed.

scholarly journals High-harmonic spectroscopy of ultrafast many-body dynamics in strongly correlated systems

2018 ◽  
Vol 12 (5) ◽  
pp. 266-270 ◽  
Author(s):  
R. E. F. Silva ◽  
Igor V. Blinov ◽  
Alexey N. Rubtsov ◽  
O. Smirnova ◽  
M. Ivanov
Keyword(s):  
High Harmonic ◽  
Strongly Correlated Systems ◽  
Strongly Correlated ◽  
Many Body ◽  
Correlated Systems ◽  
Body Dynamics

scholarly journals Regularized Second-Order Correlation Methods for Extended Systems

2021 ◽  
Author(s):  
Elisabeth Keller ◽  
Theodoros Tsatsoulis ◽  
Karsten Reuter ◽  
Johannes T. Margraf
Keyword(s):  
Computational Cost ◽  
Cost Effective ◽  
Strongly Correlated Systems ◽  
Second Order ◽  
Strongly Correlated ◽  
Many Body ◽  
Correlated Systems ◽  
Extended Systems ◽  
Moller Plesset ◽  
The One

While many-body wavefunction theory has long been established as a powerful framework for highly accurate molecular quantum chemistry, these methods have only fairly recently been applied to extended systems in a significant scale. This is due to the high computational cost of such calculations, requiring efficient implementations and ample computing resources. To further aggravate this, second-order Møller-Plesset perturbation theory (MP2) (the most cost effective wavefuntion method) is known to diverge or fail for some prototypical condensed matter systems like the homogeneous electron gas (HEG). In this paper, we explore how the issues of MP2 for metallic and strongly correlated systems can be ameliorated through regularization. To this end, two regularized second-order methods (including a new, size-extensive Brillioun-Wigner approach) are applied to the HEG, the one-dimensional Hubbard model and the graphene-water interaction energy. We find that regularization consistently leads to improvements over the MP2 baseline and that different regularizers are appropriate for metallic and strongly correlated systems, respectively.

scholarly journals Spin-imbalance in a 2D Fermi-Hubbard system

Science ◽  
2017 ◽  
Vol 357 (6358) ◽  
pp. 1385-1388 ◽  
Author(s):  
Peter T. Brown ◽  
Debayan Mitra ◽  
Elmer Guardado-Sanchez ◽  
Peter Schauß ◽  
Stanimir S. Kondov ◽  
...  
Keyword(s):  
Hubbard Model ◽  
Metallic Phase ◽  
Strong Interactions ◽  
Temperature Phase ◽  
Strongly Correlated ◽  
Many Body ◽  
Open Questions ◽  
Antiferromagnetic Correlations ◽  
Strongly Correlated Fermions ◽  
Many Body Systems

The interplay of strong interactions and magnetic fields gives rise to unusual forms of superconductivity and magnetism in quantum many-body systems. Here, we present an experimental study of the two-dimensional Fermi-Hubbard model—a paradigm for strongly correlated fermions on a lattice—in the presence of a Zeeman field and varying doping. Using site-resolved measurements, we revealed anisotropic antiferromagnetic correlations, a precursor to long-range canted order. We observed nonmonotonic behavior of the local polarization with doping for strong interactions, which we attribute to the evolution from an antiferromagnetic insulator to a metallic phase. Our results pave the way to experimentally mapping the low-temperature phase diagram of the Fermi-Hubbard model as a function of both doping and spin polarization, for which many open questions remain.

scholarly journals String patterns in the doped Hubbard model

Science ◽  
2019 ◽  
Vol 365 (6450) ◽  
pp. 251-256 ◽  
Author(s):  
Christie S. Chiu ◽  
Geoffrey Ji ◽  
Annabelle Bohrdt ◽  
Muqing Xu ◽  
Michael Knap ◽  
...  
Keyword(s):  
Hubbard Model ◽  
Strongly Correlated Electrons ◽  
Cold Atom ◽  
Strongly Correlated ◽  
Many Body ◽  
Spin Order ◽  
Open Questions ◽  
Modern Physics ◽  
Many Body Systems ◽  
The Individual

Understanding strongly correlated quantum many-body states is one of the most difficult challenges in modern physics. For example, there remain fundamental open questions on the phase diagram of the Hubbard model, which describes strongly correlated electrons in solids. In this work, we realize the Hubbard Hamiltonian and search for specific patterns within the individual images of many realizations of strongly correlated ultracold fermions in an optical lattice. Upon doping a cold-atom antiferromagnet, we find consistency with geometric strings, entities that may explain the relationship between hole motion and spin order, in both pattern-based and conventional observables. Our results demonstrate the potential for pattern recognition to provide key insights into cold-atom quantum many-body systems.

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