DMRG Studies of the Spin-Half Heisenberg System with Dimerization and Frustration

R. Chitra; Swapan K. Pati; H. R. Krishnamurthy; D. Sen; S. Ramasesha

doi:10.1103/PhysRevB.52.6581

paper

DMRG Studies of the Spin-Half Heisenberg System with Dimerization and Frustration

arXiv:cond-mat/9412016 · doi:10.1103/PhysRevB.52.6581

Abstract

Using the density matrix renormalization group technique, we study the ground state phase diagram and other low-energy properties of an isotropic antiferromagnetic spin-half chain with both dimerization and frustration, i.e., an alternation $δ$ of the nearest neighbor exchanges and a next-nearest-neighbor exchange $J_{2}$ . For $δ = 0$ , the system is gapless for $J_{2} < J_{2 c}$ and has a gap for $J_{2} > J_{2 c}$ where $J_{2 c}$ is about $0.241$ . For $J_{2} = J_{2 c}$ , the gap above the ground state grows as $δ$ to the power $0.667 \pm 0.001$ . In the $J_{2} - δ$ plane, there is a disorder line $2 J_{2} + δ = 1$ . To the left of this line, the peak in the static structure factor $S (q)$ is at $q_{ma x} = π$ (Neel phase), while to the right of the line, $q_{ma x}$ decreases from $π$ to $π /2$ as $J_{2}$ is increased to large values (spiral phase). For $δ = 1$ , the system is equivalent to two coupled chains as on a ladder and it is gapped for all values of the interchain coupling.

17 pages in tex; figures not included; this published version differs significantly from the original, particularly in some numbers

DMRG Studies of the Spin-Half Heisenberg System with Dimerization and Frustration

Abstract

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