Macroscopic Quantum Coherence of an Antiferromagnetic Spin Chain with Biaxial Anisotropy in an External Magnetic Field

We in this paper provide a sine-Gordon model of (1+1)-dimensions in which macroscopic quantum coherence of domain walls may be observed. The tunneling amplitude in field models of (1+1)-dimensions, such as sine-Gordon, is negligible small at zero temperature. In the long, but finite-length chain at finite temperature it is possible to have a finite, but still very small one. In the present model of the antiferromagnetic spin chain with biaxial anisotropy in an external magnetic field, in which the height of the sine-Gordon barrier can be tuned, the tunneling amplitude is shown to be enhanced by adjusting the external parameter.