Probing the critical floating phase of the S=5/2 Heisenberg antiferromagnetic zigzag spin chain

The physics of S = 1/2 one-dimensional spin chain is quite rich, and they offer a viable ground for the experimental realization of correlated quantum states with exotic fractional excitations. On the other hand, the low-dimensional system with large spin (i.e., S =5/2 ) has not been studied extensively as the quantum effects are not supposed to be prominent in these materials. However, a competing interaction such as a second nearest neighbor interaction J2 may introduce frustration and generate new exotic magnetic phases of matter. Surprinsingly, in the rich phase diagram obtained by DMRG of the J1-J2-J3 frustrated spin chain model, a critical “floating” phase was discovered in which the dominant wave-vector q is not “frozen” to any specific value, but “floats” or changes continuously all over the phase. This floating phase appears to be a generic feature of a zigzag chain with half-integer spins S ≥ 3/2, and given its large area in the phase diagram, it is expected to be realized experimentally. Here, we believe we found an excellent realization of such model, with the S = 5/2 quasi-one-dimensional spin system Bi3FeMo2O12.