3 research outputs found
Terahertz conductivity of the heavy-fermion compound UNi2Al3
We have studied the optical properties of the heavy-fermion compound UNi2Al3
at frequencies between 100 GHz and 1 THz (3 cm^-1 and 35 cm^-1), temperatures
between 2 K and 300 K, and magnetic fields up to 7 T. From the measured
transmission and phaseshift of radiation passing through a thin film of
UNi2Al3, 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^-1 for the a-axis
and around 4.5 cm^-1 for the c-axis. This feature is visible already at 30 K,
much higher than the Neel 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 UNi2Al3, and this might also be
the case for UPd2Al3 and UPt3, where a similar maximum in the optical
conductivity was observed previously.Comment: 7 pages, 9 figure
Observing the anisotropic optical response of the heavy-fermion compound UNi2Al3
The optical conductivity of heavy fermions can reveal fundamental properties
of the charge carrier dynamics in these strongly correlated electron systems.
Here we extend the conventional techniques of infrared optics on heavy fermions
by measuring the transmission and phase shift of THz radiation that passes
through a thin film of UNi2Al3, a material with hexagonal crystal structure. We
deduce the optical conductivity in a previously not accessible frequency range,
and furthermore we resolve the anisotropy of the optical response (parallel and
perpendicular to the hexagonal planes). At frequencies around 7cm^-1, we find a
strongly temperature-dependent and anisotropic optical conductivity that -
surprisingly - roughly follows the dc behavior.Comment: 3 pages, 2 figures, accepted for proceedings of QCnP 200
Investigation of GRIN2A in common epilepsy phenotypes
Recently, mutations and deletions in the GRIN2A gene have been identified to predispose to benign and severe idiopathic focal epilepsies (IFE), revealing a higher incidence of GRIN2A alterations among the more severe phenotypes. This study aimed to explore the phenotypic boundaries of GRIN2A mutations by investigating patients with the two most common epilepsy syndromes: (i) idiopathic generalized epilepsy (IGE) and (ii) temporal lobe epilepsy (TLE). Whole exome sequencing data of 238 patients with IGE as well as Sanger sequencing of 84 patients with TLE were evaluated for GRIN2A sequence alterations. Two additional independent cohorts comprising 1469 IGE and 330 TLE patients were screened for structural deletions (>40. kb) involving GRIN2A. Apart from a presumably benign, non-segregating variant in a patient with juvenile absence epilepsy, neither mutations nor deletions were detected in either cohort. These findings suggest that mutations in GRIN2A preferentially are involved in genetic variance of pediatric IFE and do not contribute significantly to either adult focal epilepsies as TLE or generalized epilepsies