4,722 research outputs found
Observation of a kink during the formation of the Kondo resonance band in a heavy-fermion system
We have shown that the kink behavior in the spectral function of a heavy fermion can appear during the formation of the Kondo resonance (KR) band and the hybridization gap. We have investigated the heavy fermion compound CeCoGe2, using a combined approach of the density functional theory and the dynamical mean field theory. Low temperature T spectral functions show dispersive KR states, similarly to the recent experimental observation. During the evolution from the non-f conduction band state at high T to the dispersive KR band state at low T, which have topologically different band shapes, we have found the existence of kinks in the non-f spectral function near the Fermi level E-F. The observation of kink is clearly in correspondence with the multiple temperature scales of the formation of the KR band.X1186sciescopu
Critical behaviors of cascading dynamics on multiplex two-dimensional lattices
We study the critical phenomena of viable clusters in multiplex
two-dimensional lattices using numerical simulations. We identify viable sites
on multiplex lattices using two cascading algorithms: the cascade of
activations (CA) and deactivations (CD). We found that the giant viable
clusters identified by CA and CD processes exhibit different critical
behaviors. Specifically, the critical phenomena of CA processes are consistent
with the ordinary bond percolation on a single layer but CD processes exhibit
the critical behaviors consistent with mutual percolation on multiplex
lattices. In addition, we computed the susceptibility of cascading dynamics by
using the concept of ghost field. Our results suggest that the CA and CD
processes generate viable clusters in different ways.Comment: 6 pages, 6 figure
Temperature-dependent Fermi surface evolution in heavy fermion CeIrIn5
In Cerium-based heavy electron materials, the 4f electron's magnetic moments
bind to the itinerant quasiparticles to form composite heavy quasiparticles at
low temperature. The volume of the Fermi surfacein the Brillouin zone
incorporates the moments to produce a "large FS" due to the Luttinger theorem.
When the 4f electrons are localized free moments, a "small FS" is induced since
it contains only broad bands of conduction spd electrons. We have addressed
theoretically the evolution of the heavy fermion FS as a function of
temperature, using a first principles dynamical mean-field theory (DMFT)
approach combined with density functional theory (DFT+DMFT). We focus on the
archetypical heavy electrons in CeIrIn5, which is believed to be near a quantum
critical point. Upon cooling, both the quantum oscillation frequencies and
cyclotron masses show logarithmic scaling behavior (~ ln(T_0/T)) with different
characteristic temperatures T_0 = 130 and 50 K, respectively. The resistivity
coherence peak observed at T ~ 50 K is the result of the competition between
the binding of incoherent 4f electrons to the spd conduction electrons at Fermi
level and the formation of coherent 4f electrons.Comment: 5 pages main article,3 figures for the main article, 2 page
Supplementary information, 2 figures for the Supplementary information.
Supplementary movie 1 and 2 are provided on the
webpage(http://www-ph.postech.ac.kr/~win/supple.html
Nonvolatile memories using deep traps formed in HfOā by Nb ion implantation
We report nonvolatile memories (NVMs) based on deep-energy trap levels formed in HfOā by metal ion implantation. A comparison of Nb- and Ta-implanted samples shows that suitable charge-trapping centers are formed in Nb-implanted samples, but not in Ta-implanted samples. This is consistent with density-functional theory calculations which predict that only Nb will form deep-energy levels in the bandgap of HfOā. Photocurrent spectroscopy exhibits characteristics consistent with one of the trap levels predicted in these calculations. Nb-implanted samples showing memory windows in capacitanceāvoltage (V) curves always exhibit current (I) peaks in IāV curves, indicating that NVM effects result from deep traps in HfOā. In contrast, Ta-implanted samples show dielectric breakdowns during the IāV sweeps between 5 and 11 V, consistent with the fact that no trap levels are present. For a sample implanted with a fluence of 10Ā¹Ā³Nb cmā»Ā², the charge losses after 10ā“ s are ā¼9.8 and ā¼25.5% at room temperature (RT) and 85Ā°C, respectively, and the expected charge loss after 10 years is ā¼34% at RT, very promising for commercial NVMs
Dimerization-Induced Fermi-Surface Reconstruction in IrTe2
We report a de Haas-van Alphen (dHvA) oscillation study on IrTe2 single crystals showing complex dimer formations. By comparing the angle dependence of dHvA oscillations with band structure calculations, we show distinct Fermi surface reconstruction induced by a 1/5-type and a 1/8-type dimerizations. This verifies that an intriguing quasi-two-dimensional conducting plane across the layers is induced by dimerization in both cases. A phase transition to the 1/8 phase with higher dimer density reveals that local instabilities associated with intra-and interdimer couplings are the main driving force for complex dimer formations in IrTe2.X11149sciescopu
Singlet superfield extension of the minimal supersymmetric standard model with Peccei-Quinn symmetry and a light pseudoscalar Higgs boson at the LHC
Motivated by the mu-problem and the axion solution to the strong CP-problem,
we extend the MSSM with one more chiral singlet field . The underlying
PQ-symmetry allows only one more term in the superpotential. The
spectrum of the Higgs system includes a light pseudoscalar (in addition
to the standard CP-even Higgs boson), predominantly decaying to two photons:
. Both Higgs bosons might be in the range accessible to
current LHC experiments.Comment: 5 pages with 3 figure
Supersymmetric codimension-two branes and U(1)_R mediation in 6D gauged supergravity
We construct a consistent supersymmetric action for brane chiral and vector
multiplets in a six-dimensional chiral gauged supergravity. A nonzero brane
tension can be accommodated by allowing for a brane-localized Fayet-Iliopoulos
term proportional to the brane tension. When the brane chiral multiplet is
charged under the bulk U(1)_R, we obtain a nontrivial coupling to the extra
component of the U(1)_R gauge field strength as well as a singular scalar
self-interaction term. Dimensionally reducing to 4D on a football
supersymmetric solution, we discuss the implication of such interactions for
obtaining the U(1)_R D-term in the 4D effective supergravity. By assuming the
bulk gaugino condensates and nonzero brane F- and/or D-term for the uplifting
potential, we have all the moduli stabilized with a vanishing cosmological
constant. The brane scalar with nonzero R charge then gets a soft mass of order
the gravitino mass. The overall sign of the soft mass squared depends on the
sign of the R charge as well as whether the brane F- or D-term dominates.Comment: 28 pages, no figures, version to appear in JHE
A descriptive epidemiological study on the patterns of occupational injuries in a coastal area and a mountain area in Southern China
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