Article

# Monte Carlo simulation of monolayer graphene at non-zero temperature

Physical Review B (Impact Factor: 3.77). 08/2011; 84(7):075123. DOI:10.1103/PhysRevB.84.075123
Source: arXiv

ABSTRACT We present results from lattice simulations of a monolayer graphene model at
non-zero 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 delta governing the response of the order parameter at criticality to
an external source has a value close to 15. The critical coupling on a lattice
with temporal extent N_t=32 (T=1/(N_t a_t) where a_t is the temporal lattice
spacing) and spatial extent N_s=64 is very close to infinite coupling. The
value of the transition temperature normalized with the zero temperature
fermion mass gap Delta_0 is given by T_BKT/Delta_0=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
Upsilon and the fermion thermal mass Delta_T(T), the later providing evidence
for a pseudogap phase with Delta_T>0 extending to arbitrarily high T.

0 0
·
0 Bookmarks
·
57 Views