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SYFQ: Symposium Frustrated Quantum Systems

SYFQ 1: Frustrated Quantum Systems

SYFQ 1.3: Invited Talk

Wednesday, September 10, 2025, 12:05–12:45, ZHG008

Quantum disorder and quantum critical states in organic systems with triangular lattices — •Kazushi Kanoda — Max Planck Institute for Solid State Research, Stuttgart, Germany — University of Stuttgart, Germany — University of Tokyo, Japan

The exploration of quantum materials that exhibit macroscopic manifestations of quantum fluctuations and their associated novel properties is currently a focal point in condensed matter physics. Geometrically frustrated lattices, where interparticle interactions conflict with one another, serve as platforms for observing such phenomena. In this symposium, we will review the current status of research on quantum spin liquids (QSLs), with a focus on the triangular-lattice organic system κ-(BEDT-TTF)2Cu2(CN)3. Recent experimental results suggest that this system exhibits (neutral) Fermi-liquid-like behavior, followed by an instability of quantum critical nature at lower temperatures. Next, we will also discuss a metallic and superconducting system, κ-(BEDT-TTF)4Hg2.89Br8, which is a candidate for the doped QSL. In this case, we show both the non-Fermi liquid behavior and the quantum critical characteristics of the normal state, along with its superconducting nature, characterized by a pseudogap and reduced superfluid density. Finally, we will address the interrelationships between the low-temperature phases present in these two systems.

Keywords: Quantum spin liquid; Triangular lattice; Organic materilas; quantum critical state