Field and Polarization Dependent Quantum Spin Dynamics in Honeycomb Magnet Na${}_2$Co${}_2$TeO${}_6$: Magnetic Excitations and Continuum

Abstract

We report terahertz spectroscopic measurements of quantum spin dynamics in the spin-1/2 honeycomb magnet Na${}_2$Co${}_2$TeO${}_6$ as a function of applied magnetic field with different terahertz polarizations. Distinct field dependencies of the resolved spin dynamics are identified in three regimes, which are separated by two critical fields at $B_{c1}\approx 7$ and $B_{c2}\approx 10$ T. A polarization selective continuum is observed in the intermediate phase, featuring spin fluctuations of a proximate quantum spin liquid.

6 pages, 4 figures

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