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|๚:||ฝฌ23N824๚( ) 13:30`|
|Date and time:||24th Aug (Wed.) 13:30`|
|Place:||SPring-8, "HOUKOUKAN" seminar room|
|Title:||Magnetic field-induced freezing of a quantum spin-liquid on the kagome lattice|
|Speaker:||Dr. Minki Jeong (Laboratoire de Physique des Solides, Univ. Paris-Sud 11)|
Quantum spin-liquids are exotic states of matter where interacting spins continue to fluctuate down to absolute zero temperature due to strong quantum fluctuations. In particular, two-dimensional spin-liquids in frustrated quantum magnets have been long sought after since Andersonfs proposals for a resonating valence bond phase and its possible link to the high-Tc cuprate superconductivity. Only recently, a few candidate materials have emerged. For example, Herbertsmithite, ZnCu3(OH)6Cl2, is a unique representative of the quantum (S=1/2) kagome antiferromagnet, which displays a gapless spin-liquid behaviors down to 50 mK, 1/4000th of its exchange energy. In this talk, I will present our recent NMR results which uncover an instability of the spin-liquid phase of Herbertsmithite toward a spin-solid phase induced by an applied magnetic field. We find the zero-temperature phase transition appears at a finite magnetic field much smaller than the exchange energy scale. I will discuss the implication of this quantum critical point in light of the recent theoretical proposals for the gapless or gapped spin-liquid ground-state of the quantum kagome Heisenberg antiferromagnet as well as the quantum phase transition driven by perturbative Dzyaloshinskii-Moriya interaction.