Quantum disordered phase in a doped antiferromagnet

C. Kübert, A. Muramatsu

C. Kübert, A. Muramatsu

A quantitative description of the transition to a quantum disordered phase in a doped antiferromagnet is obtained with a U (1) gauge theory, where the gap in the spin-wave spectrum determines the strength of the gauge fields. They mediate an attractive long-range interaction whose possible bound states correspond to charge-spin separation and pairing.

Indrani Bose

V. I. Belinicher, João da Providência

Michele Fabrizio, R. Mélin

We present a numerical study of single-chain models of doped spin-1 compounds. We use low-energy effective one-dimensional models for both the cases of paramagnetic and spin-1/2 doping. In the case of paramagnetic doping, the effective model is equivalent to the bond disordered spin-1/2 chain model recently analysed by means of the real space renormalization group by Hyman and Yang. By means of exact diagonalizations in the XX limit, we confirm the stability of the Haldane phase for weak disorder. Above a critical amount of disorder, the effective model flows to the so-called random singlet fixed point. In the case of spin-1/2 doping, we argue that the Haldane phase should be destabilized even for weak disorder. This picture is not in contradiction with existing experimental data. We also discuss the possible occurrence of (unobserved) antiferromagnetically ordered phases.

Rong Yu, Tommaso Roscilde, Stephan Haas