2,809 research outputs found
An Infrared study of the Josephson vortex state in high-Tc cuprates
We report the results of the c-axis infrared spectroscopy of La_{2-x} Sr_x
CuO_4 in high magnetic field oriented parallel to the CuO_2 planes. A
significant suppression of the superfluid density with magnetic field rho_s(H)
is observed for both underdoped (x=0.125) and overdoped (x=0.17) samples. We
show that the existing theoretical models of the Josephson vortex state fail to
consistently describe the observed effects and discuss possible reasons for the
discrepancies
Heavy fermion fluid in high magnetic fields: an infrared study of CeRuSb
We report a comprehensive infrared magneto-spectroscopy study of
CeRuSb compound revealing quasiparticles with heavy effective mass
m, with a detailed analysis of optical constants in fields up to 17 T. We
find that the applied magnetic field strongly affects the low energy
excitations in the system. In particular, the magnitude of m 70
m (m is the quasiparticle band mass) at 10 K is suppressed by as much
as 25 % at 17 T. This effect is in quantitative agreement with the mean-field
solution of the periodic Anderson model augmented with a Zeeman term
Signatures of electron-boson coupling in half-metallic ferromagnet MnGe: study of electron self-energy obtained from infrared spectroscopy
We report results of our infrared and optical spectroscopy study of a
half-metallic ferromagnet MnGe. This compound is currently being
investigated as a potential injector of spin polarized currents into germanium.
Infrared measurements have been performed over a broad frequency (50 - 50000
cm) and temperature (10 - 300 K) range. From the complex optical
conductivity we extract the electron self-energy
. The calculation of is based on novel
numerical algorithms for solution of systems of non-linear equations. The
obtained self-energy provides a new insight into electron correlations in
MnGe. In particular, it reveals that charge carriers may be coupled to
bosonic modes, possibly of magnetic origin
Strong-coupling Effects in cuprate High- Superconductors by magnetooptical studies
Signatures of strong coupling effects in cuprate high- superconductors
have been authenticated through a variety of spectroscopic probes. However, the
microscopic nature of relevant excitations has not been agreed upon. Here we
report on magneto-optical studies of the CuO plane carrier dynamics in a
prototypical high- superconductor YBaCuO (YBCO).
Infrared data are directly compared with earlier inelastic neutron scattering
results by Dai \textit{et al}. [Nature (London) \textbf{406}, 965 (2000)]
revealing a characteristic depression of the magnetic resonance in H \textit{c} field less than 7 T. This analysis has allowed us to critically
assess the role of magnetic degrees of freedom in producing strong coupling
effects for YBCO system.Comment: 4 pages, two figure
Improving knowledge of Funiculina quadrangularis and vulnerable marine ecosystems in the south Adriatic
The Adriatic Sea is one of the most exploited areas in the Mediterranean; however, a large part of the South Adriatic Sea remains largely unexplored. Unfortunately, direct and indirect anthropogenic impacts are increasing exponentially, causing a loss of flagship species and threatening ecosystem functioning. This has led to several international conventions demanding better protection and management of sensitive species and areas worldwide. Soft mud facies bearing the sea pen Funiculina quadrangularis are indicators of vulnerable marine ecosystems (VMEs). This study aimed a) to contribute to the knowledge on the distributions of F. quadrangularis and VMEs, and b) to assess the main threats, thus enabling better identification of areas that need protection and ecosystem base management. The results show that F. quadrangularis are distributed from 160 m to 400 m depth, with the highest population density of 0.83 colony/m(2) reported in the Adriatic Sea at a 162 m depth. However, using video ground truthing, we registered stresses on deep-sea habitats originating from fishery and marine litter. Further research is needed to ascertain other potentially vulnerable areas. Moreover, international discussion is needed to determine future steps for the protection and sustainable use of resources beyond national jurisdictions
Pressure-tuning of the c-f hybridization in Yb metal detected by infrared spectroscopy up to 18 GPa
It has been known that the elemental Yb, a divalent metal at mbient pressure,
becomes a mixed-valent metal under external pressure, with its valence reaching
~2.6 at 30 GPa. In this work, infrared spectroscopy has been used to probe the
evolution of microscopic electronic states associated with the valence
crossover in Yb at external pressures up to 18 GPa. The measured infrared
reflectivity spectrum R(w) of Yb has shown large variations with pressure. In
particular, R(w) develops a deep minimum in the mid-infrared, which shifts to
lower energy with increasing pressure. The dip is attributed to optical
absorption due to a conduction c-f electron hybridization state, similarly to
those previously observed for heavy fermion compounds. The red shift of the dip
indicates that the - hybridization decreases with pressure, which is
consistent with the increase of valence.Comment: 2 pages, to appear in J. Phys. Soc. Jpn. Supp
Electronic Structure and Charge Dynamics of Huesler Alloy Fe2TiSn Probed by Infrared and Optical Spectroscopy
We report on the electrodynamics of a Heusler alloy Fe2TiSn probed over four
decades in energy: from the far infrared to the ultraviolet. Our results do not
support the suggestion of Kondo-lattice behavior inferred from specific heat
measurements. Instead, we find a conventional Drude-like response of free
carriers, with two additional absorption bands centered at around 0.1 and 0.87
eV. The latter feature can be interpreted as excitations across a pseudogap, in
accord with band structure calculations.Comment: 3 pages, 4 figure
Infrared probe of the anomalous magnetotransport of highly oriented pyrolytic graphite in the extreme quantum limit
We present a systematic investigation of the magnetoreflectance of highly
oriented pyrolytic graphite in magnetic field B up to 18 T . From these
measurements, we report the determination of lifetimes tau associated with the
lowest Landau levels in the quantum limit. We find a linear field dependence
for inverse lifetime 1/tau(B) of the lowest Landau levels, which is consistent
with the hypothesis of a three-dimensional (3D) to 1D crossover in an
anisotropic 3D metal in the quantum limit. This enigmatic result uncovers the
origin of the anomalous linear in-plane magnetoresistance observed both in bulk
graphite and recently in mesoscopic graphite samples
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