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arXiv · 1208.1664

Power-law dependence of the optical conductivity observed in the quantum spin-liquid compound \kappa-(BEDT-TTF)2Cu2(CN)3

Sebastian Elsasser·Dan Wu·Martin Dressel·John A. Schlueter
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Abstract

The Mott-insulator \kappa-(BEDT-TTF)_2Cu_2(CN)_3 is the prime candidate of a quantum spin liquid with puzzling magnetic properties. Our THz and infrared investigations reveal that also the charge dynamics does not follow the expectations for a Mott insulator. The frequency-dependent conductivity exhibits a power-law behavior $\sigma_1(\omega)\propto \omega^n$ that grows stronger as the temperature decreases and extends all the way through the far-infrared. With $n\approx 0.8$ to 1.5 we obtain a significantly smaller exponent than predicted by Ng and Lee [Phys. Rev. Lett. {\bf 99}, 156402 (2007)]. We suggest fluctuations becomes important in the spin-liquid state and couple to the electrodynamic properties differently compared to the antiferromagnetic Mott insulator \kappa-(BEDT-TTF)_2Cu[N(CN)_2]Cl. We discuss the various possibilities of how charge fluctuations are influenced by the presence or absence of magnetic order.

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Sebastian Elsasser, Dan Wu, Martin Dressel, John A. Schlueter. 2012-08-08. Power-law dependence of the optical conductivity observed in the quantum spin-liquid compound \kappa-(BEDT-TTF)2Cu2(CN)3. https://doi.org/10.1103/physrevb.86.155150

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