Spin-liquid-like state in ferroelectric TbInO₃ with a nearly triangular lattice

Quantum spin liquids (QSL) have been continuously attracting attention since Anderson’s seminal work in 1970’s. As most visionary ideas, QSLs have been found to be relevant to many diverse branches of physics, ranging from superconductivity to quantum computing applications. Known QSL candidate compounds are typically based on geometrically frustrated magnetic lattices, such as the kagome and triangular (TL) lattices. After decades of activity, their properties are still enigmatic, and the number of strong QSL candidates is limited. We describe a recently-discovered QSL candidate TbInO₃, containing nearly-triangular layers of non-Kramers Tb³⁺ ions. No signs of static magnetic order are found down to the temperatures two orders of magnitude smaller than the effective interaction energy, by a variety of complementary techniques. Inelastic neutron scattering studies reveal a broad continuum of magnetic excitations located at the TL Brillouin zone boundary that can be described in the framework of the uncorrelated nearest-neighbor valence bonds model. TbInO₃ is also ferroelectric, containing atomically-sharp domain boundaries that could host exotic states. These observations make TbInO₃ a rather unique QSL candidate, in which fluctuating quantum magnetic state is combined with ferroelectricity.