Pinning the Order: The Nature of Quantum Criticality in the Hubbard Model on Honeycomb Lattice

In numerical simulations, spontaneously broken symmetry is often detected by computing two-point correlation functions of the appropriate local order parameter. This approach, however, computes the square of the local order parameter, and so when it is small, very large system sizes at high precisio...

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Bibliographic Details
Published in:Physical review. X 2013-08, Vol.3 (3), p.031010, Article 031010
Main Authors: Assaad, Fakher F., Herbut, Igor F.
Format: Article
Language:English
Subjects:
Algorithms
Antiferromagnetism
Broken symmetry
Computer simulation
Cones
Electronic structure
Electronic systems
Electrons
Graphene
Monte Carlo simulation
Order parameters
Phase transitions
Pinning
Topological insulators
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Summary:In numerical simulations, spontaneously broken symmetry is often detected by computing two-point correlation functions of the appropriate local order parameter. This approach, however, computes the square of the local order parameter, and so when it is small, very large system sizes at high precisions are required to obtain reliable results. Alternatively, one can pin the order by introducing a local symmetry-breaking field and then measure the induced local order parameter infinitely far from the pinning center. The method is tested here at length for the Hubbard model on honeycomb lattice, within the realm of the projective auxiliary-field quantum Monte Carlo algorithm. With our enhanced resolution, we find a direct and continuous quantum phase transition between the semimetallic and the insulating antiferromagnetic states with increase of the interaction. The single-particle gap, measured in units of Hubbard U , tracks the staggered magnetization. An excellent data collapse is obtained by finite-size scaling, with the values of the critical exponents in accord with the Gross-Neveu universality class of the transition.
ISSN:2160-3308
2160-3308
DOI:10.1103/PhysRevX.3.031010