2006/05/15 by Weihong Zheng, Zheng, Weihong, Chris Hamer +3
Physics and Astronomy · #FOS: Physical sciences #Statistical Mechanics (cond-mat.stat-mech) #Strongly Correlated Electrons (cond-mat.str-el) #cond-mat.stat-mech #cond-mat.str-el
paper · pdf · doi:10.48550/arxiv.cond-mat/0605370
4 pages, 8 figures
arxiv created 2006/05/15 · arxiv updated 2009/12/01
We calculate the excitation spectrum and spectral weights of the alternating antiferromagnetic-ferromagnetic spin-half Heisenberg chain with exchange couplings J and -|λ|J as a power series in λ. For small |λ|, the gapped one-particle spectrum has a maximum at k=0 and there is a rich structure of bound (and anti-bound) states below (and above) the 2-particle continuum. As |λ| is increased past unity the spectrum crosses over to the Haldane regime, where the peak shifts away from k=0, the one particle states merge with the bottom of the continuum near k=0, and the spectral weights associated with the one-particle states become very small. Extrapolation of the spectrum to large |λ| confirms that the ground state energy and excitation gap map onto those of the spin-one chain.