Quantum Spin Singlet Ground State with Large Excitation Gap in the S = 3/2 quasi-1D van der Waals materials MoX3 (X = I, Br)
The study investigated MoI3 and MoBr3, quasi-one-dimensional van der Waals materials, to determine if they possess a quantum spin singlet ground state instead of classical antiferromagnetic order. Experimental data showed features consistent with both classical Néel order and a gapped quantum spin chain behavior. Calculations confirmed that the large excitation gap is due to strong exchange dimerization along the chains, providing evidence for novel quantum magnetism.