With The Frustrated Quasi-one Dimensional Spin Chain Ground State Spin-image Study

The properties of the ground state and the lower-energy excited state of the lower dimensional Antiferromagnetic Heisenberg(AFH) model has been one of the central areas of the theoretical research in recent ten years. Lower dimensional AFH models show some novel properties such as quasi-long-range-order,spin gap,quantum phase transition, etc.The properties of the ground state of AFH model is effected on by the dimensionality of the system. By periodically doping spins (side spin) beside every spin site of the same sublattice of the one dimension AFH linear chain, we construct a kind of quasi-one-dimensional (QOD) AFH spin model. The effective exchange integral for the interaction between the nearest neighbor spins on chain is J . The effective exchange integral for the interaction between the side spin and the nearest neighbor spin on chain is also J andαJ is for the side spin and the next nearest neighbor spin on chain. With the changing ofα, we investigate the spin picture of the ground state,spin gap and other properties of the system .The calculations by exact diagonalization show that the system exhibits a neel phase, a canted phase and a quantum disorder phase as a function of the frustration parameterα.From the analysis of Spin Wave theory and Green Function method, the system displays a neel phase in littleαregime. Under the effect of the frustration, significant changes take place in the system. The frustration relieves the gap-degeneracy of two optical branches. And it softens the spectrum in acoustic mode whereas doesn't soften the spectra in optical mode. Also, the frustration moves down obviously one of two spectra in optical mode. It means the frustration makes the spin-wave excitation described by spectrum in optical mode easier and more important. The status of spin on the chain changes more easily than that of side spin under the effect of frustration. The weakening of magnetic order in ground state becomes strong with the strengthening of frustration.The result of high-order coupled cluster method also shows that in one regime the...