6533b871fe1ef96bd12d18e7

RESEARCH PRODUCT

Terahertz conductivity of the heavy-fermion compound UNi2Al3

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We have studied the optical properties of the heavy-fermion compound UNi${}_{2}$Al${}_{3}$ at frequencies between 100 GHz and 1 THz (3 and 35 cm${}^{\ensuremath{-}1}$), temperatures between 2 and 300 K, and magnetic fields up to 7 T. From the measured transmission and phase shift of radiation passing through a thin film of UNi${}_{2}$Al${}_{3}$, we have directly determined the frequency dependence of the real and imaginary parts of the optical conductivity (or permittivity, respectively). At low temperatures the anisotropy of the optical conductivity along the $a$ and $c$ axes is about 1.5. The frequency dependence of the real part of the optical conductivity shows a maximum at low temperatures, around 3 cm${}^{\ensuremath{-}1}$ for the $a$ axis and around 4.5 cm${}^{\ensuremath{-}1}$ for the $c$ axis. This feature is visible already at 30 K, much higher than the N\'eel temperature of 4.6 K, and it does not depend on external magnetic fields as high as 7 T. We conclude that this feature is independent of the antiferromagnetic order for UNi${}_{2}$Al${}_{3}$, and this might also be the case for UPd${}_{2}$Al${}_{3}$ and UPt${}_{3}$, where a similar maximum in the optical conductivity was observed previously [Dressel et al., Phys. Rev. Lett. 88, 186404 (2002)].