289 research outputs found
Fractionalization and Fermi surface volume in heavy fermion compounds: the case of YbRh Si
We establish an effective theory for heavy fermion compounds close to a zero
temperature Anti-Ferromagnetic (AF) transition. Coming from the heavy Fermi
liquid phase across to the AF phase, the heavy electron fractionalizes into a
light electron, a bosonic spinon and a {\it new} excitation: a spinless
fermionic field. Assuming this field acquires dynamics and dispersion when one
integrates out the high energy degrees of freedom, we give a scenario for the
volume of its Fermi surface through the phase diagram. We apply our theory to
the special case of YbRh(Si Ge) where we recover, within
experimental resolution, several low temperature exponents for transport and
thermodynamics.Comment: 4 pages, 5 figure
collective mode as A Raman resonance in cuprate superconductors
We discuss the possible existence a spin singlet excitation with charge
(-mode) originating the Raman resonance in cuprate
superconductors. This -mode relates the -wave superconducting singlet
pairing channel to a -wave charge channel. We show that the boson
forms a particle-particle bound state below the threshold of the
particle-hole continuum where is the maximum -wave gap. Within a
generalized random phase approximation and Bethe-Salpether approximation study,
we find that this mode has energies similar to the resonance observed by
Inelastic Neutron Scattering (INS) below the superconducting (SC) coherent peak
at in various SC cuprates compounds. We show that it is a very good
candidate for the resonance observed in Raman scattering below the
peak in the symmetry. Since the -mode sits in the channel,
it may be observable via Raman, X -ray or Electron Energy Loss Spectroscopy
probes
Ultrafast xâray sources@f|
Timeâresolved spectroscopy (with a 2 psec temporal resolution) of plasmas produced by the interaction between solid targets and a high contrast subpicosecond table top terawatt (T3) laser at 1016 W/cm2, is used to study the basic processes which control the xâray pulse duration. Short xâray pulses have been obtained by spectral selection or by plasma gradient scalelength control. Timeâdependent calculations of the atomic physics [Phys. Fluids B 4, 2007, 1992] coupled to a FokkerâPlanck code [Phys. Rev. Lett. 53, 1461, 1984] indicate that it is essential to take into account the nonâMaxwellian character of the electron distribution for a quantitative analysis of the experimental results.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70417/2/PFBPEI-5-7-2676-1.pd
Density of states for dirty d-wave superconductors: A unified and dual approach for different types of disorder
A two-parameter field theoretical representation is given of a 2-dimensional
dirty d-wave superconductor that interpolates between the Gaussian limit of
uncorrelated weak disorder and the unitary limit of a dilute concentration of
resonant scatterers. It is argued that a duality holds between these two
regimes from which follows that a linearly vanishing density of states in the
Gaussian limit transforms into a diverging one in the unitary limit arbitrarily
close to the Fermi energy
Realization of Haldane's Exclusion Statistics in a Model of Electron-Phonon Interactions
We discuss an integrable model describing one-dimensional electrons
interacting with two-dimensional anharmonic phonons. In the low temperature
limit it is possible to decouple phonons and consider one-dimensional
excitations separately. They have a trivial two-body scattering matrix and obey
fractional statistics. As far as we know the original model presents the first
example of a model with local bare interactions generating purely statistical
interactions between renormalized particles. As a by-product we obtain
non-trivial thermodynamic equations for the interacting system of
two-dimensional phonons.Comment: 4 page
Temperature and ac Effects on Charge Transport in Metallic Arrays of Dots
We investigate the effects of finite temperature, dc pulse, and ac drives on
the charge transport in metallic arrays using numerical simulations. For finite
temperatures there is a finite conduction threshold which decreases linearly
with temperature. Additionally we find a quadratic scaling of the
current-voltage curves which is independent of temperature for finite
thresholds. These results are in excellent agreement with recent experiments on
2D metallic dot arrays. We have also investigated the effects of an ac drive as
well as a suddenly applied dc drive. With an ac drive the conduction threshold
decreases for fixed frequency and increasing amplitude and saturates for fixed
amplitude and increasing frequency. For sudden applied dc drives below
threshold we observe a long time power law conduction decay.Comment: 6 pages, 7 postscript figure
Thermodynamic evidence for broken fourfold rotational symmetry in the hidden-order phase of URu2Si2
Despite more than a quarter century of research, the nature of the
second-order phase transition in the heavy-fermion metal URuSi remains
enigmatic. The key question is which symmetry is being broken below this
"hidden order" transition. We review the recent progress on this issue,
particularly focusing on the thermodynamic evidence from very sensitive
micro-cantilever magnetic torque measurements that the fourfold rotational
symmetry of the underlying tetragonal crystal is broken. The angle dependence
of the torque under in-plane field rotation exhibits the twofold oscillation
term, which sets in just below the transition temperature. This observation
restricts the symmetry of the hidden order parameter to the - or
-type, depending on whether the time reversal symmetry is preserved or
not.Comment: 7 pages, 5 figures, brief review article for Physica C Special Issue
on Stripes and Electronic Liquid Crystals in Strongly Correlated Systems,
updated references and added some discussio
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