scholarly journals Broken-Symmetry Ground States of the Heisenberg Model on the Pyrochlore Lattice

2021 ◽  
Vol 11 (4) ◽  
Author(s):  
Nikita Astrakhantsev ◽  
Tom Westerhout ◽  
Apoorv Tiwari ◽  
Kenny Choo ◽  
Ao Chen ◽  
...  
Keyword(s):  
Heisenberg Model ◽  
Ground States ◽  
Broken Symmetry

Two-dimensional spin-1 frustrated Heisenberg model with valence-bond ground states

2007 ◽  
Vol 76 (5) ◽  
Author(s):  
Zi Cai ◽  
Shu Chen ◽  
Supeng Kou ◽  
Yupeng Wang
Keyword(s):  
Heisenberg Model ◽  
Valence Bond ◽  
Ground States ◽  
Two Dimensional

scholarly journals Correction: Localization in the SCAN meta-generalized gradient approximation functional leading to broken symmetry ground states for graphene and benzene

2020 ◽  
Vol 22 (42) ◽  
pp. 24813-24813
Author(s):  
Yubo Zhang ◽  
Wenqing Zhang ◽  
David J. Singh
Keyword(s):  
Ground States ◽  
Chem Phys ◽  
Broken Symmetry ◽  
Generalized Gradient ◽  
Generalized Gradient Approximation ◽  
Phys Chem Chem Phys

Correction for ‘Localization in the SCAN meta-generalized gradient approximation functional leading to broken symmetry ground states for graphene and benzene’ by Yubo Zhang et al., Phys. Chem. Chem. Phys., 2020, 22, 19585–19591, DOI: 10.1039/D0CP03567J.

THE t-J AND FRUSTRATED HEISENBERG MODELS: A STATUS REPORT ON NUMERICAL STUDIES

1991 ◽  
Vol 05 (06n07) ◽  
pp. 907-935 ◽  
Author(s):  
ELBIO DAGOTTO
Keyword(s):  
Numerical Methods ◽  
Heisenberg Model ◽  
Ground States ◽  
Status Report ◽  
Heisenberg Antiferromagnet ◽  
Numerical Work ◽  
Active Search ◽  
Numerical Studies ◽  
Dynamical Properties ◽  
Frustrated Spin

Recent numerical work on the t-J model and the frustrated spin-[Formula: see text] Heisenberg antiferromagnet is reviewed. Lanczos results are mainly discussed but other methods are also mentioned. Static and dynamical properties of one and more holes in the t-J model are presented. The current active search for nontrivial ground states of the frustrated Heisenberg model is summarized. It is concluded that numerical methods are providing useful information in the study of these models.

scholarly journals THE SAWTOOTH CHAIN: FROM HEISENBERG SPINS TO HUBBARD ELECTRONS

2008 ◽  
Vol 22 (25n26) ◽  
pp. 4418-4433 ◽  
Author(s):  
J. RICHTER ◽  
O. DERZHKO ◽  
A. HONECKER
Keyword(s):  
Low Temperature ◽  
Hubbard Model ◽  
Heisenberg Model ◽  
Chemical Potential ◽  
Ground States ◽  
High Magnetic Fields ◽  
Thermodynamic Quantities ◽  
Saturation Field ◽  
Ground State Degeneracy ◽  
Characteristic Features

We report on recent studies of the spin-half Heisenberg and the Hubbard model on the sawtooth chain. For both models we construct a class of exact eigenstates which are localized due to the frustrating geometry of the lattice for a certain relation of the exchange (hopping) integrals. Although these eigenstates differ in details for the two models because of the different statistics, they share some characteristic features. The localized eigenstates are highly degenerate and become ground states in high magnetic fields (Heisenberg model) or at certain electron fillings (Hubbard model), respectively. They may dominate the low-temperature thermodynamics and lead to an extra low-temperature maximum in the specific heat. The ground-state degeneracy can be calculated exactly by a mapping of the manifold of localized ground states onto a classical hard-dimer problem, and explicit expressions for thermodynamic quantities can be derived which are valid at low temperatures near the saturation field for the Heisenberg model or around a certain value of the chemical potential for the Hubbard model, respectively.

scholarly journals Localization in the SCAN meta-generalized gradient approximation functional leading to broken symmetry ground states for graphene and benzene

2020 ◽  
Vol 22 (35) ◽  
pp. 19585-19591 ◽  
Author(s):  
Yubo Zhang ◽  
Wenqing Zhang ◽  
David J. Singh
Keyword(s):  
Ground States ◽  
Spin Symmetry ◽  
Broken Symmetry ◽  
Generalized Gradient ◽  
Generalized Gradient Approximation

SCAN over localizes orbitals leading to spin symmetry broken ground states in graphene and benzene.

scholarly journals Revisiting the Electronic Structure of Cobalt-Porphyrin Nitrene and Carbene Radicals with NEVPT2-CASSCF Calculations: Doublet versus Quartet Ground States

2021 ◽  
Author(s):  
Nicolaas P. van Leest ◽  
Bas de Bruin
Keyword(s):  
Ground State ◽  
Ground States ◽  
Broken Symmetry ◽  
Transfer Reactions ◽  
Group Transfer ◽  
Cobalt Porphyrin ◽  
Spin Counting ◽  
State Wavefunctions ◽  
Radical Character ◽  
Spin Ground State

Cobalt-porphyrin complexes are established catalysts for carbene and nitrene radical group transfer reactions. The key carbene, mono- and bis-nitrene radical complexes coordinated to [Co(TPP)] (TPP = tetraphenylporphyrin) have previously been investigat-ed with a variety of experimental techniques and supporting (single-reference) DFT calculations that indicated doublet (S = ½) ground states for all three species. In this contribution we revisit their electronic structures with multireference NEVPT2-CASSCF calculations to investigate possible multireference contributions to the ground state wavefunctions. The carbene ([Co<sup>III</sup>(TPP)(•CHCO<sub>2</sub>Et)]) and mono-nitrene ([Co<sup>III</sup>(TPP)(•NNs)]) radical complexes were confirmed to have uncomplicated doublet ground states, although a higher carbene or nitrene radical character and a lower Co‒C/N bond order was found in the NEVPT2-CASSCF calculations. Supported by EPR analysis and spin counting, paramagnetic molar susceptibility determination and NEVPT2-CASSCF calculations, we report that the cobalt-porphyrin bis-nitrene complex ([Co<sup>III</sup>(TPP•)(•NNs)<sub>2</sub>]) has a quartet (S = 3/2) spin ground state, with a thermally assessable multireference & multideterminant ‘broken-symmetry’ doublet spin excited state. A spin flip on the porphyrin-centered unpaired electron allows for interconversion between the quartet and broken-symmetry doublet spin states, with an approximate 10- and 200-fold higher Boltzmann population of the quartet at room tempera-ture or 10 K, respectively.<br>

NUMERICAL STUDIES OF STRONGLY CORRELATED ELECTRONIC MODELS

1991 ◽  
Vol 05 (01n02) ◽  
pp. 77-111 ◽  
Author(s):  
Elbio Dagotto
Keyword(s):  
Numerical Methods ◽  
Heisenberg Model ◽  
Ground States ◽  
Strongly Correlated ◽  
Heisenberg Antiferromagnet ◽  
Numerical Work ◽  
Active Search ◽  
Numerical Studies ◽  
Dynamical Properties

Recent numerical work on strongly correlated electronic models using the Lanczos approach is reviewed. In particular static and dynamical properties of the Hubbard, t—J (with one, two and more holes) and the spin-½ Heisenberg antiferromagnet are presented. An attempt to summarize the current active search for nontrivial ground states of the frustrated Heisenberg model is made. Numerical methods like the Lanczos technique are providing useful information in the study of these models.

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