Spin-Orbital Excitation Continuum and Anomalous Electron-Phonon Interaction in the Mott InsulatorLaTiO3
Physical Review Letters
Raman scattering experiments on stoichiometric, Mott-insulating LaTiO_3 over a wide range of excitation energies reveal a broad electronic continuum which is featureless in the paramagnetic state, but develops a gap of ∼ 800 cm^-1 upon cooling below the Néel temperature T_N = 146 K. In the antiferromagnetic state, the spectral weight below the gap is transferred to well-defined spectral features due to spin and orbital excitations. Low-energy phonons exhibit pronounced Fano anomalies indicative
... of strong interaction with the electron system for T > T_N, but become sharp and symmetric for T < T_N. The electronic continuum and the marked renormalization of the phonon lifetime by the onset of magnetic order are highly unusual for Mott insulators and indicate liquid-like correlations between spins and orbitals.