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research article

Exact diagonalization study of the Hubbard-parametrized four-spin ring exchange model on a square lattice

Larsen, C. B.
•
Romer, A. T.
•
Janas, S.
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February 27, 2019
Physical Review B

We have used exact numerical diagonalization to study the excitation spectrum and the dynamic spin correlations in the s = 1/2 next-next-nearest-neighbor Heisenberg antiferromagnet on the square lattice, with additional four-spin ring exchange from higher-order terms in the Hubbard expansion. We have varied the ratio between Hubbard model parameters t/U to obtain different relative strengths of the exchange parameters, while keeping electrons localized. The Hubbard model parameters have been parametrized via an effective ring exchange coupling J(r), which have been varied between 0 J and 1.5 J. We find that ring exchange induces a quantum phase transition from a (pi, pi) ordered state to a (pi/2, pi/2) ordered state. This quantum critical point is reduced by quantum fluctuations from its mean-field value of J(r)/J = 2 to a value of similar to 1.1. At the quantum critical point, the dynamical correlation function shows a pseudocontinuum at q values between the two competing ordering vectors.

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Type
research article
DOI
10.1103/PhysRevB.99.054432
Web of Science ID

WOS:000459930900004

Author(s)
Larsen, C. B.
•
Romer, A. T.
•
Janas, S.
•
Treue, F.
•
Monsted, B.
•
Shaik, N. E.  
•
Ronnow, H. M.  
•
Lefmann, K.
Date Issued

2019-02-27

Publisher

AMER PHYSICAL SOC

Published in
Physical Review B
Volume

99

Issue

5

Article Number

054432

Subjects

Materials Science, Multidisciplinary

•

Physics, Applied

•

Physics, Condensed Matter

•

Materials Science

•

Physics

•

superconductivity

Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
LQM  
Available on Infoscience
June 18, 2019
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/157888
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