Field- and polarization-dependent quantum spin dynamics in the honeycomb magnet <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Na</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>Co</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>TeO</mml:mi><mml:mn>6</mml:mn></mml:msub></mml:mrow></mml:math>: Magnetic excitations and continuum

Abstract

We report terahertz spectroscopic measurements of quantum spin dynamics in the spin-1/2 honeycomb magnet ${\mathrm{Na}}_{2}{\mathrm{Co}}_{2}{\mathrm{TeO}}_{6}$ 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 ${B}_{c1}\ensuremath{\approx}7$ and ${B}_{c2}\ensuremath{\approx}10$ T. A polarization-selective continuum is observed in the intermediate phase, featuring spin fluctuations of a proximate quantum spin liquid.

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