QSL and Deconfined Quantum Critical Point

A Quantum Spin Liquid (QSL) is a state in which quantum fluctuations prevent the spins from entering any types of ordered states at zero temperature. QSLs are relevant to many diverse branches of physics, ranging from superconductivity to quantum computing applications. Unfortunately, the QSL is notoriously difficult to detect in experiments because most of the existing probes are local, while massive entanglement and non-local excitations are the QSL’s defining properties. Inelastic neutron scattering (INS) is widely considered one of the key tools for probing the QSL state because it gives access to fractional magnetic excitations. Fractional excitations are created in pairs in INS and therefore are revealed as broad signals that are spread over a continuum of energy.

Figure. A broad gapless excitations centered around the M1 point, the BZ boundary in TbInO3.

For instance, we found a broad and gapless continuum of magnetic excitations, located at the Brillouin zone boundary in TbInO3. No signs of static magnetic order are found down to the temperatures 100 times smaller than the effective interaction energy. The INS data are well described by the uncorrelated nearest-neighbor valence bond model. These observations provide compelling existing evidence for a triangular-lattice-based spin liquid state in TbInO3.

Our Research

Our goal is finding new QSLs. We are interested in a triangular lattice. Low-dimensional and geometrically frustrated, triangular-lattice antiferromagnets produce novel phases, including long-range ordered states, spin glasses, valence bond solids (VBS), and QSLs. The number of strong QSL (and VBS) materials is very limited, and any newly discovered system will attract significant interest.

Our research objectives are to (1) synthesize and characterize new QSL or VBS materials; (2) study the structural and magnetic ground states using x-ray and neutron diffraction; (3) study spin excitations in different ground states of the new materials with INS; (4) understand the data in the context of existing theories, for example, the spin-1/2 Heisenberg model.

  • A. Balodhi, B. Billingsley, T. Kong, and M. G. Kim, “Synthesis, structural and magnetic characterizations of Li4Cu1-xNixTeO6 ( x = 0, 0.1, 0.2, 0.5 and 1),” Physica B 679, 415795 (2024).

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