Ground-State Properties of the Spin-1/2 Heisenberg–Ising Bond Alternating Chain with Dzyaloshinskii–Moriya Interaction

Ground-state energy is exactly calculated for the spin-1/2 Heisenberg–Ising bond alternating chain with the Dzyaloshinskii–Moriya interaction. Under certain condition, which relates a strength of the Ising, Heisenberg and Dzyaloshinskii–Moriya interactions, the ground-state energy exhibits an interesting nonanalytic behavior accompanied with a gapless excitation spectrum. PACS numbers: 05.50.+q, 05.70.Jk, 64.60.De, 75.10.Pq 1