7,196 research outputs found
Common Fermi-liquid origin of T-squared resistivity and superconductivity in n-type SrTiO3
A detailed analysis is given of the T^2 term in the resistivity observed in
electron-doped SrTiO3. Novel bandstructure data are presented, which provide
values for the bare mass, density of states, and plasma frequency of the
quasiparticles as a function of doping. It is shown that these values are
renormalized by approximately a factor 2 due to electron-phonon interaction. It
is argued that the quasiparticles are in the anti-adiabatic limit with respect
to electron-phonon interaction. The condition of anti-adiabatic coupling
renders the interaction mediated through phonons effectively non-retarded. We
apply Fermi-liquid theory developed in the 70's for the T^2 term in the
resistivity of common metals, and combine this with expressions for Tc and with
the Brinkman-Platzman-Rice (BPR) sum-rule to obtain Landau parameters of n-type
SrTiO3. These parameters are comparable to those of liquid 3He, indicating
interesting parallels between these Fermi-liquids despite the differences
between the composite fermions from which they are formed.Comment: 12 pages, 9 figure
Stratified dispersive model for material characterization using terahertz time-domain spectroscopy
We propose a novel THz material analysis approach which provides highly
accurate material parameters and can be used for industrial quality control.
The method treats the inspected material within its environment locally as a
stratified system and describes the light-matter interaction of each layer in a
realistic way. The approach is illustrated in the time-domain and
frequency-domain for two potential fields of implementation of THz technology:
quality control of (coated) paper sheets and car paint multilayers, both
measured in humid air.Comment: 4 pages, 4 figure
Spin resonance in EuTiO3 probed by time-domain GHz ellipsometry
We show an example of a purely magnetic spin resonance in EuTiO3 and the
resulting new record high Faraday rotation of 590 deg/mm at 1.6 T for 1 cm
wavelengths probed by a novel technique of magneto-optical GHz time-domain
ellipsometry. From our transmission measurements of linear polarized light we
map out the complex index of refraction in the GHz to THz range. We observe a
strong resonant absorption by magnetic dipole transitions involving the Zeeman
split S=7/2 magnetic energy levels of the Eu 2+ ions, which causes a very large
dichroism for circular polarized radiation.Comment: 4 pages, 4 figure
Mg-Ni-H films as selective coatings: tunable reflectance by layered hydrogenation
Unlike other switchable mirrors, Mg2NiHx films show large changes in
reflection that yield very low reflectance (high absorptance) at different
hydrogen contents, far before reaching the semiconducting state. The resulting
reflectance patterns are of interference origin, due to a self-organized
layered hydrogenation mechanism that starts at the substrate interface, and can
therefore be tuned by varying the film thickness. This tunability, together
with the high absorptance contrast observed between the solar and the thermal
energies, strongly suggests the use of these films in smart coatings for solar
applications.Comment: Three two-column pages with 3 figures embedded; RevTE
Many-body large polaron optical conductivity in SrTiNbO
Recent experimental data on the optical conductivity of niobium doped
SrTiO are interpreted in terms of a gas of large polarons with effective
coupling constant . The {theoretical approach takes into
account} many-body effects, the electron-phonon interaction with multiple
LO-phonon branches, and the degeneracy and the anisotropy of the Ti t
conduction band. {Based on the Fr\"{o}hlich interaction, the many-body
large-polaron theory} provides an interpretation for the essential
characteristics, except -- interestingly -- for the unexpectedly large
intensity of a peak at meV, of the observed optical conductivity
spectra of SrTiNbO \textit{without} any adjustment of
material parameters.Comment: to appear in Phys. Rev.
Surface state charge dynamics of a high-mobility three dimensional topological insulator
We present a magneto-optical study of the three-dimensional topological
insulator, strained HgTe using a technique which capitalizes on advantages of
time-domain spectroscopy to amplify the signal from the surface states. This
measurement delivers valuable and precise information regarding the surface
state dispersion within <1 meV of the Fermi level. The technique is highly
suitable for the pursuit of the topological magnetoelectric effect and axion
electrodynamics.Comment: Published version, online Sept 23, 201
Oxygen isotope effect and phase separation in the optical conductivity of (LaPr)CaMnO thin films
The optical conductivities of films of
(LaPr)CaMnO with different oxygen isotopes
(O and O) have been determined in the spectral range from 0.3 to
4.3 eV using a combination of transmission in the mid-infrared and ellipsometry
from the near-infrared to ultra-violet regions. We have found that the isotope
exchange strongly affects the optical response in the ferromagnetic phase in a
broad frequency range, in contrast to the almost isotope-independent optical
conductivity above . The substitution by O strongly suppresses the
Drude response and a mid-infrared peak while enhancing the conductivity peak at
1.5 eV. A qualitative explanation can be given in terms of the phase separation
present in these materials. Moreover, the optical response is similar to the
one extracted from measurements in polished samples and other thin films, which
signals to the importance of internal strain.Comment: 11 pages, 11 figures, to appear in PR
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