Researchers from Yonsei University, Rutgers University, KAIST, and other institutes in South Korea have discovered unconventional charge carriers in a Mott insulator at room temperature. Mott insulators are typically materials that should conduct electricity but instead behave as insulators due to the presence of strongly correlated electrons.
The researchers focused on terbium indium oxide (TbInO3), a Mott insulator with a triangular lattice structure. They grew high-quality single crystals of TbInO3 using laser floating-zone growth. Previous studies had indicated that TbInO3 exhibited quantum spin liquid behavior.
Terahertz time-domain spectroscopy was then used to analyze the TbInO3 samples. The researchers observed that the a.c. terahertz conductivity in the material was proportional to the square of the frequency of light, even at room temperature. This observation challenges the belief that unconventional excitations only exist in Mott insulators at low temperatures.
The most significant finding of the study was the discovery of unconventional charge carriers made up of a macroscopic number of quantum spins. Contrary to the common belief that charge carriers do not exist at low energy in an insulator, the researchers measured optical conductivity proportional to the square of the frequency of light, demonstrating the existence of charge carriers. Remarkably, these charge carriers remained coherent up to room temperature.
The discovery of unconventional charge carriers in Mott insulators at room temperature opens up new possibilities for further experiments and theoretical physics studies. The researchers plan to extend their research to other indium oxide compounds to explore similar effects.
The findings of this study have implications for understanding the physics of Mott insulators and could contribute to the development of fault-tolerant quantum computers that operate at room temperature.
Source: Taek Sun Jung et al. “Unconventional room-temperature carriers in the triangular-lattice Mott insulator TbInO3.” Nature Physics (2023).
– Mott insulators: Materials with structures that should conduct electricity but behave as insulators due to the presence of strongly correlated electrons.
– Quantum spin liquid: A unique phase of matter that describes a liquid-like Mott insulator without magnetic ordering.
– Terahertz time-domain spectroscopy: A technique used to measure the properties of materials with respect to terahertz frequency electromagnetic radiation.