46,930 research outputs found
Gauge coupling renormalization in orbifold field theories
We investigate the gauge coupling renormalization in orbifold field theories
preserving 4-dimensional N=1 supersymmetry in the framework of 4-dimensional
effective supergravity. As a concrete example, we consider the 5-dimensional
Super-Yang-Mills theory on a slice of AdS_5. In our approach, one-loop gauge
couplings can be determined by the loop-induced axion couplings and the tree
level properties of 4-dimensional effective supergravity which are much easier
to be computed.Comment: 18 pages, JHEP style; 1-loop corrections to gauge kinetic functions
are fully computed, references are adde
Signature of high temperature superconductivity in electron doped Sr2IrO4
Sr2IrO4 was predicted to be a high temperature superconductor upon electron
doping since it highly resembles the cuprates in crystal structure, electronic
structure and magnetic coupling constants. Here we report a scanning tunneling
microscopy/spectroscopy (STM/STS) study of Sr2IrO4 with surface electron doping
by depositing potassium (K) atoms. At the 0.5-0.7 monolayer (ML) K coverage, we
observed a sharp, V-shaped gap with about 95% loss of density of state (DOS) at
EFand visible coherence peaks. The gap magnitude is 25-30 meV for 0.5-0.6 ML K
coverage and it closes around 50 K. These behaviors exhibit clear signature of
superconductivity. Furthermore, we found that with increased electron doping,
the system gradually evolves from an insulating state to a normal metallic
state, via a pseudogap-like state and possible superconducting state. Our data
suggest possible high temperature superconductivity in electron doped Sr2IrO4,
and its remarkable analogy to the cuprates.Comment: 11 pages, 5 figure
Giant phonon anomalies in the pseudo-gap phase of TiOCl
We report infrared and Raman spectroscopy results of the spin-1/2 quantum
magnet TiOCl. Giant anomalies are found in the temperature dependence of the
phonon spectrum, which hint to unusual coupling of the electronic degrees of
freedom to the lattice. These anomalies develop over a broad temperature
interval, suggesting the presence of an extended fluctuation regime. This
defines a pseudo-gap phase, characterized by a local spin-gap. Below 100 K a
dimensionality cross-over leads to a dimerized ground state with a global
spin-gap of about 2~430 K.Comment: 4 pages, 3 figures, for further information see
http://www.peter-lemmens.d
Dynamical symmetry breaking in Gauge-Higgs unification of 5D SUSY theory
We study the dynamical symmetry breaking in the gauge-Higgs unification of
the 5D SUSY theory, compactified on an orbifold, .
This theory identifies Wilson line degrees of freedoms as ``Higgs doublets''.
We consider and SU(6) models, in which the gauge
symmetries are reduced to and , respectively, through the
orbifolding boundary conditions. Quarks and leptons are bulk fields, so that
Yukawa interactions can be derived from the 5D gauge interactions. We estimate
the one loop effective potential of ``Higgs doublets'', and analyze the vacuum
structures in these two models. We find that the effects of bulk quarks and
leptons destabilize the suitable electro-weak vacuum. We show that the
introduction of suitable numbers of extra bulk fields possessing the suitable
representations can realize the appropriate electro-weak symmetry breaking.Comment: 15 pages, 4 figures;disscutions on Higgs quartic couplings adde
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