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.

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 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.

scholarly journals Ultrafast dynamical Lifshitz transition

2021 ◽  
Vol 7 (17) ◽  
pp. eabd9275
Author(s):  
Samuel Beaulieu ◽  
Shuo Dong ◽  
Nicolas Tancogne-Dejean ◽  
Maciej Dendzik ◽  
Tommaso Pincelli ◽  
...  
Keyword(s):  
Fermi Surface ◽  
Colossal Magnetoresistance ◽  
Surface Topology ◽  
Strongly Correlated ◽  
Many Body ◽  
Time Resolved ◽  
Weyl Semimetal ◽  
Lifshitz Transition ◽  
Fermi Surface Topology ◽  
Many Body Systems

Fermi surface is at the heart of our understanding of metals and strongly correlated many-body systems. An abrupt change in the Fermi surface topology, also called Lifshitz transition, can lead to the emergence of fascinating phenomena like colossal magnetoresistance and superconductivity. While Lifshitz transitions have been demonstrated for a broad range of materials by equilibrium tuning of macroscopic parameters such as strain, doping, pressure, and temperature, a nonequilibrium dynamical route toward ultrafast modification of the Fermi surface topology has not been experimentally demonstrated. Combining time-resolved multidimensional photoemission spectroscopy with state-of-the-art TDDFT+U simulations, we introduce a scheme for driving an ultrafast Lifshitz transition in the correlated type-II Weyl semimetal Td-MoTe2. We demonstrate that this nonequilibrium topological electronic transition finds its microscopic origin in the dynamical modification of the effective electronic correlations. These results shed light on a previously unexplored ultrafast scheme for controlling the Fermi surface topology in correlated quantum materials.

scholarly journals Self-consistent effective Hamiltonian theory for fermionic many-body systems

2020 ◽  
pp. 2150019
Author(s):  
Xindong Wang ◽  
Hai-Ping Cheng
Keyword(s):  
Hubbard Model ◽  
Order Parameter ◽  
Cooper Pair ◽  
Effective Hamiltonian ◽  
Two Dimensional ◽  
Body System ◽  
Many Body ◽  
Hamiltonian Theory ◽  
Self Consistent ◽  
Many Body Systems

Using a separable many-body variational wavefunction, we formulate a self-consistent effective Hamiltonian theory for fermionic many-body system. The theory is applied to the two-dimensional (2D) Hubbard model as an example to demonstrate its capability and computational effectiveness. Most remarkably for the Hubbard model in 2D, a highly unconventional quadruple-fermion non-Cooper pair order parameter is discovered.

scholarly journals Virial expansion coefficients in the unitary Fermi gas

2020 ◽  
Author(s):  
Shimpei Endo
Keyword(s):  
Recent Progress ◽  
Cold Atoms ◽  
Virial Coefficient ◽  
Fermi Gas ◽  
Virial Expansion ◽  
Strongly Correlated ◽  
Many Body ◽  
Unitary Fermi Gas ◽  
Expansion Coefficients ◽  
Many Body Systems

Virial expansion is widely used in cold atoms to analyze high temperature strongly correlated many-body systems. As the n-th order virial expansion coefficient can be accurately obtained by exactly solving up to n-body problems, the virial expansion offers a few-body approach to study strongly correlated many-body problems. In particular, the virial expansion has successfully been applied to unitary Fermi gas. We review recent progress of the virial expansion studies in the unitary Fermi gas, in particular the fourth order virial coefficient.

scholarly journals Encoding strongly-correlated many-boson wavefunctions on a photonic quantum computer: application to the attractive Bose-Hubbard model

Quantum ◽  
2021 ◽  
Vol 5 ◽  
pp. 572
Author(s):  
Saad Yalouz ◽  
Bruno Senjean ◽  
Filippo Miatto ◽  
Vedran Dunjko
Keyword(s):  
Hubbard Model ◽  
Quantum Computer ◽  
Quantum Algorithms ◽  
Experimental System ◽  
Quantum Circuit ◽  
Continuous Variable ◽  
Computer Application ◽  
Strongly Correlated ◽  
Many Body ◽  
Boson Systems

Variational quantum algorithms (VQA) are considered as some of the most promising methods to determine the properties of complex strongly correlated quantum many-body systems, especially from the perspective of devices available in the near term. In this context, the development of efficient quantum circuit ansatze to encode a many-body wavefunction is one of the keys for the success of a VQA. Great efforts have been invested to study the potential of current quantum devices to encode the eigenstates of fermionic systems, but little is known about the encoding of bosonic systems. In this work, we investigate the encoding of the ground state of the (simple but rich) attractive Bose-Hubbard model using a Continuous-Variable (CV) photonic-based quantum circuit. We introduce two different ansatz architectures and demonstrate that the proposed continuous variable quantum circuits can efficiently encode (with a fidelity higher than 99%) the strongly correlated many-boson wavefunction with just a few layers, in all many-body regimes and for different number of bosons and initial states. Beyond the study of the suitability of the ansatz to approximate the ground states of many-boson systems, we also perform initial evaluations of the use of the ansatz in a variational quantum eigensolver algorithm to find it through energy minimization. To this end we also introduce a scheme to measure the Hamiltonian energy in an experimental system, and study the effect of sampling noise.

scholarly journals Automatic differentiation applied to excitations with projected entangled pair states

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Boris Ponsioen ◽  
Fakher Assaad ◽  
Philippe Corboz
Keyword(s):  
Automatic Differentiation ◽  
Optimization Methods ◽  
Two Dimensions ◽  
Strongly Correlated ◽  
Many Body ◽  
Tensor Networks ◽  
Tensor Network ◽  
New Ideas ◽  
Half Filling ◽  
Many Body Systems

The excitation ansatz for tensor networks is a powerful tool for simulating the low-lying quasiparticle excitations above ground states of strongly correlated quantum many-body systems. Recently, the two-dimensional tensor network class of infinite projected entangled-pair states gained new ground state optimization methods based on automatic differentiation, which are at the same time highly accurate and simple to implement. Naturally, the question arises whether these new ideas can also be used to optimize the excitation ansatz, which has recently been implemented in two dimensions as well. In this paper, we describe a straightforward way to reimplement the framework for excitations using automatic differentiation, and demonstrate its performance for the Hubbard model at half filling.

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