Double sine-Gordon chain

The thermodynamic properties of the double sine-Gordon chain are studied both analytically and numerically. Particular attention is given to the regime in which there are two different kinks (small and large) on the chain. The shape and energy of kinks are found in the continuum approximation. Comparison is made with numerical determination of the kink energies. The free energy, entropy, etc. of the chain are found. They are dominated by the small kinks. To see evidence for the participation of the large kinks the fluctuation in chain position and its equation of state are examined. The current carried by the chain is calculated. An unusual polarization precursor to activated conductivity is found. The polarization precursor is determined by the small kinks; the conductivity is determined by the large kinks.