2,915 research outputs found
121,123Sb NQR as a microscopic probe in Te doped correlated semimetal FeSb2 : emergence of electronic Griffith phase, magnetism and metallic behavior %
nuclear quadrupole resonance (NQR) was applied to
in the low doping regime (\emph{x = 0, 0.01} and
\emph{0.05}) as a microscopic zero field probe to study the evolution of
\emph{3d} magnetism and the emergence of metallic behavior. Whereas the NQR
spectra itself reflects the degree of local disorder via the width of the
individual NQR lines, the spin lattice relaxation rate (SLRR) probes
the fluctuations at the - site. The fluctuations originate either from
conduction electrons or from magnetic moments. In contrast to the semi metal
with a clear signature of the charge and spin gap formation in
, the 1\% doped system exhibits
almost metallic conductivity and a almost filled gap. A weak divergence of the
SLRR coefficient points towards the
presence of electronic correlations towards low temperatures wheras the
\textit{5\%} doped sample exhibits a much larger divergence in the SLRR
coefficient showing . According to the specific heat
divergence a power law with is expected for the SLRR.
Furthermore -doped as a disordered paramagnetic metal might be a
platform for the electronic Griffith phase scenario. NQR evidences a
substantial asymmetric broadening of the NQR spectrum for the
\emph{5\%} sample. This has purely electronic origin in agreement with the
electronic Griffith phase and stems probably from an enhanced - bond
polarization and electronic density shift towards the atom inside
- dumbbell
Dynamic LFSRs as an alternative to LFSRs in extended fields - A comparative study
Linear feedback shift registers (LFSRs) with dynamic feedback (DLFSRs) and LFSRs defined over extended fields i.e., over GF(2n), constitute building blocks of many pseudorandom sequence generators used in stream ciphers. In this work, the advantages and disadvantages of using DLSFR instead of LFSR in GF(2n) are analyzed. The work is based on the possibility of obtaining a DLFSR in GF(2) equivalent to an LFSR in GF(2n), given that both structures present equivalent binary models formed by interleaved sequences. Likewise, the possibility of using DLFSR on binary vectors is proposed in order to take advantage of the word lengths of current processors
Anomalous specific heat jump in the heavy fermion superconductor CeCoIn
We study the anomalously large specific heat jump and its systematic change
with pressure in CeCoIn superconductor. Starting with the general free
energy functional of the superconductor for a coupled electron boson system, we
derived the analytic result of the specific heat jump of the strong coupling
superconductivity occurring in the coupled electron boson system. Then using
the two component spin-fermion model we calculate the specific heat coefficient
both for the normal and superconducting states and show a good
agreement with the experiment of CeCoIn. Our result also clearly
demonstrated that the specific heat coefficient of a coupled electron
boson system can be freely interpreted as a renormalization either of the
electronic or of the bosonic degrees of freedom.Comment: 5 pages, 2 figure
Quantum transport of two-dimensional Dirac fermions in SrMnBi2
We report two-dimensional quantum transport in SrMnBi single crystals.
The linear energy dispersion leads to the unusual nonsaturated linear
magnetoresistance since all Dirac fermions occupy the lowest Landau level in
the quantum limit. The transverse magnetoresistance exhibits a crossover at a
critical field from semiclassical weak-field dependence to the
high-field linear-field dependence. With increase in the temperature, the
critical field increases and the temperature dependence of
satisfies quadratic behavior which is attributed to the Landau level splitting
of the linear energy dispersion. The effective magnetoresistant mobility
cm/Vs is derived. Angular dependent magnetoresistance
and quantum oscillations suggest dominant two-dimensional (2D) Fermi surfaces.
Our results illustrate the dominant 2D Dirac fermion states in SrMnBi and
imply that bulk crystals with Bi square nets can be used to study low
dimensional electronic transport commonly found in 2D materials like graphene.Comment: 5 papges, 4 figure
Enhanced Thermoelectric Power and Electronic Correlations in RuSe
We report the electronic structure, electric and thermal transport properties
of RuIrSe (). RuSe is a semiconductor that
crystallizes in a cubic pyrite unit cell. The Seebeck coefficient of RuSe
exceeds -200 V/K around 730 K. Ir substitution results in the suppression
of the resistivity and the Seebeck coefficient, suggesting the removal of the
peaks in density of states near the Fermi level. RuIrSe
shows a semiconductor-metal crossover at about 30 K. The magnetic field
restores the semiconducting behavior. Our results indicate the importance of
the electronic correlations in enhanced thermoelectricity of RuSb.Comment: 6 pages, 4 figure
Magnetism in La2O3(Fe1-xMnx)2Se2 tuned by Fe/Mn ratio
We report the evolution of structural and magnetic properties in
La2O3(Fe1-xMnx)2Se2. Heat capacity and bulk magnetization indicate an increased
ferromagnetic component of the long-range magnetic order and possible increased
degree of frustration. Atomic disorder on Fe(Mn) sites suppresses the
temperature of the long-range order whereas intermediate alloys show a rich
magnetic phase diagram.Comment: 7 pages, 7 figure
Roles of Critical Valence Fluctuations in Ce- and Yb-Based Heavy Fermion Metals
The roles of critical valence fluctuations of Ce and Yb are discussed as a
key origin of several anomalies observed in Ce- and Yb-based heavy fermion
systems. Recent development of the theory has revealed that a magnetic field is
an efficient control parameter to induce the critical end point of the
first-order valence transition. Metamagnetism and non-Fermi liquid behavior
caused by this mechanism are discussed by comparing favorably with CeIrIn5,
YbAgCu4, and YbIr2Zn20. The interplay of the magnetic order and valence
fluctuations offers a key concept for understanding Ce- and Yb-based systems.
It is shown that suppression of the magnetic order by enhanced valence
fluctuations gives rise to the coincidence of the magnetic-transition point and
valence-crossover point at absolute zero as a function of pressure or magnetic
field. The interplay is shown to resolve the outstanding puzzle in CeRhIn5 in a
unified way. The broader applicability of this newly clarified mechanism is
discussed by surveying promising materials such as YbAuCu4, beta-YbAlB4, and
YbRh2Si2.Comment: 17 pages, 8 figures, invited paper in special issue on strongly
correlated electron system
β models for random hypergraphs with a given degree sequence
We introduce the beta model for random hypergraphs in order to represent
the occurrence of multi-way interactions among agents in a social network. This model
builds upon and generalizes the well-studied beta model for random graphs, which instead only considers pairwise interactions. We provide two algorithms for fitting the
model parameters, IPS (iterative proportional scaling) and fixed point algorithm, prove
that both algorithms converge if maximum likelihood estimator (MLE) exists, and provide algorithmic and geometric ways of dealing the issue of MLE existence
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