Probing the continuum scattering and magnetic collapse in single-crystalline α-Li2IrO3 by Raman spectroscopy

Raman spectroscopy has been applied to investigate the lattice and magnetic excitations of the honeycomb Kitaev material α-Li2IrO3. The temperature-dependent Raman spectra give evidence for an unusual magnetic excitation, typified by a broad continuum. The integrated intensity of this Raman continuum does not follow the bosonic statistics expected for the conventional insulating magnets, which indicates the emergence of itinerant Majorana fermions from spin fractionalization in α-Li2IrO3. In addition, the Raman results under pressures resolve one critical pressure at Pc=4.1GPa with structural and magnetic phase transitions, signaled by the in-plane Ir-Ir bond dimerization and magnetic collapse, and the system turns into a correlated band insulator above Pc.