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第三回目セミナーのご案内をいたします。

講　師：Dr. Tessa Cookmeyer 
所　属：University of California, Santa Barbara/KITP
題　目：Triangular lattice magnets: hidden order and dimer criticality
日　時：2026年 4月 3日（金） 11:00~12:00　オンラインのみ
Zoom：https://us02web.zoom.us/j/87426990484?pwd=5GmyKbKJj7kRReO80GKJ2CbPBaJkL0.1
Meeting ID: 874 2699 0484
Passcode: 802033

Abstract:
The triangular lattice, with its geometric frustration, has always been of particular interest in quantum magnets. In this talk, I will discuss recent experiments on two triangular-lattice quantum magnets, TmZn2GaO5 and K2Co(SeO)2, and our theoretical work surrounding them. I’ll argue that TmZn2GaO5, despite lacking magnetic Bragg peaks, exhibits a quadrupolar “order” with well-defined and measurable magnons. With its sister compound TmMgGaO4, it straddles a phase transition seen in the transverse-field Ising model on the triangular lattice. The second compound, K2Co(SeO)2, appears to enter a supersolid phase at low-temperatures, but we instead focus on the intermediate temperature region. We propose that its experimental features may be captured from a quantum dimer model and may be inside the critical fan of the Roksahr-Kivelson critical point.