Chinese Physics

Charge and spin gaps in the dimerized Hubbard model

Guo-Hui Ding, Ye Fei, Xu Bo-wei

Published Aug 1, 2000• 2 citations

Abstract

By using the bosonization and renormalization group methods, we have studied the low energy physical properties in the one-dimensional dimerized Hubbard model. The formation of charge and spin gaps is investigated both for the half-filled electron band and away from the half-filled band. The scaling laws of the charge and spin gaps with the dimerization parameter Δ and the repulsive interaction strength U are obtained.

DOI: 10.1088/1009-1963/9/8/012

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Chinese Physics

Charge and spin gaps in the dimerized Hubbard model

Guo-Hui Ding, Ye Fei, Xu Bo-wei

Published Aug 1, 2000• 2 citations

Publisher

Abstract

DOI: 10.1088/1009-1963/9/8/012

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arXiv:cond-mat/0407114Physical Review BAug 31, 200432 citations

The one-dimensional

\mathrm{SU}(n)

Hubbard model is investigated numerically for

n=2

, 3, 4, and 5 at half-filling and

1∕n

filling using the density-matrix renormalization-group method. The energy gaps and various quantum information entropies are calculated. In the half-filled case, finite spin and charge gaps are found for arbitrary positive

U

n>2

. Furthermore, it is shown that the transition to the gapped phase at

{U}_{c}=0

is of Kosterlitz-Thouless type and is accompanied by a bond dimerization both for even and odd

n

. In the

1∕n

-filled case, the transition has similar features as the metal-insulator transition in the half-filled SU(2) Hubbard model. The charge gap opens exponentially slowly for

U>{U}_{c}=0

, the spin sector remains gapless, and the ground state is nondimerized.

J

. This Mott insulator is characterized by the bond-charge-density-wave order or spontaneously dimerization. In the weak-coupling regime where the spin-charge separation holds approximately, the critical point separating the gapless and gapped spin liquid phases is ${U}_{c}\ensuremath{\sim}J∕2$. However, as

J

increases, the spin-charge couplings become important and the critical point

{U}_{c}

is significantly suppressed and eventually tends to zero as $J\ensuremath{\rightarrow}\ensuremath{\infty}$. Away from half-filling, the charge gap completely collapses but the spin gap persists.