Level crossing, spin structure factor and quantum phases of the frustrated spin-1/2 chain with first and second neighbor exchange

Manoranjan Kumar, Aslam Parvej, Zoltán G. Soos

The spin-1/2 chain with isotropic Heisenberg exchange $J_1$, $J_2>0$ between first and second neighbors is frustrated for either sign of J1. Its quantum phase diagram has critica…