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Monte Carlo simulation of monolayer graphene at nonzero temperature

DOI: 10.1103/PhysRevB.84.075123 DOI Help

Authors: Wes Armour (Diamond Light Source) , Simon Hands (University of Wales, Swansea) , Costas Strouthos (University of Cyprus)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Review B , VOL 84 (7)

State: Published (Approved)
Published: August 2011

Abstract: We present results from lattice simulations of a monolayer graphene model at nonzero temperature. At low temperatures for sufficiently strong coupling the model develops an excitonic condensate of particle-hole pairs corresponding to an insulating phase. The Berezinskii-Kosterlitz-Thouless phase transition temperature is associated with the value of the coupling where the critical exponent δ governing the response of the order parameter at criticality to an external source has a value close to 15. The critical coupling on a latticewith temporal extent Nt = 32 [T = 1/(Ntat) where at is the temporal lattice spacing] and spatial extent Ns = 64 is very close to infinite coupling. The value of the transition temperature normalized with the zero-temperature fermion mass gap Δ0 is given by TBKT/Δ0 = 0.055(2). This value provides an upper bound on the transition temperature, because simulations closer to the continuum limit where the full U(4) symmetry is restored may result in an even lower value. In addition, we measured the helicity modulus Υ and the fermion thermal mass ΔT (T ), the latter providing evidence for a pseudogap phase with ΔT > 0 extending to arbitrarily high T . Analysis of the dispersion relation suggests that the Fermi velocity is not sensitive to thermal effects.

Subject Areas: Physics

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