4,623 research outputs found
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
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
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
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
The Missing Link: Magnetism and Superconductivity
The effect of magnetic moments on superconductivity has long been a
controversial subject in condensed matter physics. While Matthias and
collaborators experimentally demonstrated the destruction of superconductivity
in La by the addition of magnetic moments (Gd), it has since been suggested
that magnetic fluctuations are in fact responsible for the development of
superconducting order in other systems. Currently this debate is focused on
several families of unconventional superconductors including high-Tc cuprates,
borocarbides as well as heavy fermion systems where magnetism and
superconductivity are known to coexist. Here we report a novel aspect of
competition and coexistence of these two competing orders in an interesting
class of heavy fermion compounds, namely the 1-1-5 series: CeTIn5 where T=Co,
Ir, or Rh. Our optical experiments indicate the existence of regions in
momentum space where local moments remain unscreened. The extent of these
regions in momentum space appears to control both the normal and
superconducting state properties in the 1-1-5 family of heavy fermion (HF)
superconductors.Comment: 6 pages, 2 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
Dysprosium-carboxylate nanomeshes with tunable cavity size and assembly motif through ionic interactions
We report the design of dysprosium directed metallo-supramolecular architectures on a pristine Cu(111) surface. By an appropriate selection of the ditopic molecular linkers equipped with terminal carboxylic groups (TPA, PDA and TDA species), we create reticular and mononuclear metal–organic nanomeshes of tunable internodal distance, which are stabilized by eight-fold Dy⋯O interactions. A thermal annealing treatment for the reticular Dy:TDA architecture gives rise to an unprecedented quasi-hexagonal nanostructure based on dinuclear Dy clusters, exhibiting a unique six-fold Dy⋯O bonding motif. All metallo-supramolecular architectures are stable at room temperature. Our results open new avenues for the engineering of supramolecular architectures on surfaces incorporating f-block elements forming thermally robust nanoarchitectures through ionic bonds
Calculation of Optical Conductivity, Resistivity and Thermopower of Filled Skutterudite CeRuSb based on a Realistic Tight-binding Model with Strong Correlation
The filled-skutterudite compound CeRuSb shows a pseudo-gap
structure in the optical conductivity spectra similar to the Kondo insulators,
but metallic behavior below 80 K. The resistivity shows a large peak at 80 K,
and the Seebeck coefficient is positive and also shows a large peak at nearly
the same temperature. In order to explain all these features, a simplified
tight-binding model, which captures the essential features of the band
calculation, is proposed. Using this model and introducing the correlation
effect within the framework of the dynamical mean field approximation and the
iterative perturbation theory, the temperature dependences of the optical
conductivity, resistivity and the Seebeck coefficient are calculated, which can
explain the experiments.Comment: 4 pages, 6 figure
Optical and thermodynamic properties of the high-temperature superconductor HgBa_2CuO_4+delta
In- and out-of-plane optical spectra and specific heat measurements for the
single layer cuprate superconductor Hg-1201 at optimal doping (Tc = 97 K) are
presented. Both the in-plane and out-of-plane superfluid density agree well
with a recently proposed scaling relation rho_{s}=sigma_{dc}T_{c}. It is shown
that there is a superconductivity induced increase of the in-plane low
frequency spectral weight which follows the trend found in underdoped and
optimally doped Bi-2212 and optimally doped Bi-2223. We observe an increase of
optical spectral weight which corresponds to a change in kinetic energy of
approximately 0.5 meV/Cu which is more than enough to explain the condensation
energy. The specific heat anomaly is 10 times smaller than in YBCO and 3 times
smaller than in Bi-2212. The shape of the anomaly is similar to the one
observed in YBCO showing that the superconducting transition is governed by
thermal fluctuations.Comment: 11 pages, 13 figure
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