Unconventional room-temperature carriers in the triangular-lattice Mott insulator TbInO3

Abstract

Previous work has suggested that at very low temperatures TbInO3 hosts an unconventional quantum ground state. Terahertz time-domain spectroscopy measurements of its excitations show that related exotic effects can persist to room temperature. The strong correlations between electrons in Mott insulator materials may produce highly entangled many-body states with unconventional emergent excitations. The signatures of such excitations, if any, are commonly believed to be observable only at low temperatures. Here, we challenge this common belief and show using terahertz time-domain spectroscopy that exotic carriers exist even at room temperature in TbInO3, a candidate material for realizing a low-temperature quantum spin-liquid phase. In particular, over the entire temperature range of 1.5-300 K, we observe a quadratic frequency dependence in the real part of the in-plane optical conductivity as well as Fano asymmetry of an optical phonon mode strongly interacting with the excitation continuum. These features are robust even under external magnetic fields of up to 7 T. Our data confirm the presence of emergent charge carriers within the Mott charge gap of TbInO3, suggesting that it is possible to probe and manipulate highly entangled quantum many-body states at room temperature.