Ground state and finite temperature signatures of quantum phase transitions in the half-filled Hubbard model on a honeycomb lattice

Thereza Paiva; R. T. Scalettar; W. Zheng; R. R. P. Singh; J. Oitmaa

doi:10.1103/PhysRevB.72.085123

paper

Ground state and finite temperature signatures of quantum phase transitions in the half-filled Hubbard model on a honeycomb lattice

arXiv:cond-mat/0406535 · doi:10.1103/PhysRevB.72.085123

Abstract

We investigate ground state and finite temperature properties of the half-filled Hubbard model on a honeycomb lattice using quantum monte carlo and series expansion techniques. Unlike the square lattice, for which magnetic order exists at T=0 for any non-zero $U$ , the honeycomb lattice is known to have a semi-metal phase at small $U$ and an antiferromagnetic one at large $U$ . We investigate the phase transition at T=0 by studying the magnetic structure $an d co m p r ess ibi l i t y u s in g q u an t u mm o n t ec a r l os im u l a t i o n s an d b y c a l c u l a t in g t h es u b l a tt i ce ma g n e t i z a t i o n, u ni f or m s u sce pt ibi l i t y, s p in - w a v e an d s in g l e h o l e$ U_c/t $in t h er an g e 4 - 5. F ini t e t e m p er a t u r es i g na t u r eso f t hi s p ha se t r an s i t i o na r esee nin t h e b e ha v i or o f t h es p ec i f i c h e a t,$ C(T) $, w hi c h c han g es f r o ma tw o - p e ak e d s t r u c t u r e f or$ U>U_c $t o a o n e - p e ak e d s t r u c t u r e f or$ U < U_c $. F u r t h er m or e, t h e$ U $d e p e n d e n ceo f t h e l o w t e m p er a t u r ecoe f f i c i e n t o f$ C(T) $e x hibi t s anan o ma l y a t$ U \approx U_c$.

11 pages, 19 figures

Ground state and finite temperature signatures of quantum phase transitions in the half-filled Hubbard model on a honeycomb lattice

Abstract

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