Abstract
We report a direct measurement of the low-frequency optical conductivity of large-area single-crystal herbertsmithite, a promising spin-liquid candidate material, by means of terahertz time-domain spectroscopy. In the spectral range below 1.4 THz, we observe a contribution to the real part of the in-plane conductivity from the spin degree of freedom. This spin-induced conductivity exhibits a power-law dependence on frequency with . Our observation is consistent with the theoretically predicted low-frequency conductivity arising from an emergent gauge field of a gapless U(1) Dirac spin liquid.
- Received 15 April 2013
DOI:https://doi.org/10.1103/PhysRevLett.111.127401
© 2013 American Physical Society