23,594 research outputs found
Three-loop HTLpt thermodynamics at finite temperature and chemical potential
In this proceedings we present a state-of-the-art method of calculating
thermodynamic potential at finite temperature and finite chemical potential,
using Hard Thermal Loop perturbation theory (HTLpt) up to
next-to-next-leading-order (NNLO). The resulting thermodynamic potential
enables us to evaluate different thermodynamic quantities including pressure
and various quark number susceptibilities (QNS). Comparison between our
analytic results for those thermodynamic quantities with the available lattice
data shows a good agreement.Comment: 5 pages, 6 figures, conference proceedings of XXI DAE-BRNS HEP
Symposium, IIT Guwahati, December 2014; to appear in 'Springer Proceedings in
Physics Series
Local magnetization nucleated by non-magnetic impurities in Fe-based superconductors
We study impurity-induced magnetic order within a five-band Hubbard model
relevant to the normal paramagnetic phase of iron-based superconductors. The
existence of the local magnetic order is explained in terms of an
impurity-enhancement of states near the Fermi level, and we map out the
resulting phase diagram of the existence of magnetization as a function of
impurity strength and Coulomb correlations. In particular, the presence of
impurity-induced magnetism in only a certain range of potential scattering
strengths can be understood from the specific behavior of the impurity resonant
state.Comment: 8 pages, 3 figure
Enhancing Superconductivity by Disorder
We study two mechanisms for enhancing the superconducting transition
temperature Tc by nonmagnetic disorder in both conventional (sign-preserving
gaps) and unconventional (sign-changing gaps) superconductors (SC). In the
first scenario, relevant to multi-band systems in the dilute impurity limit of
both conventional and unconventional SC, we demonstrate how favorable density
of states enhancements driven by resonant states in off-Fermi-level bands, lead
to significant enhancements of Tc in the condensate formed by the
near-Fermi-level bands. The second scenario focuses on the dense impurity limit
where random disorder-generated local density of states modulations cause a
boosted Tc for conventional SC with short coherence lengths. We analyze the
basic physics of both mechanisms within simplified models, and discuss the
relevance to existing materials.Comment: 6 pages, 4 figure
Pinning of stripes by local structural distortions in cuprate high-Tc superconductors
We study the spin-density wave (stripe) instability in lattices with mixed
low-temperature orthorhombic (LTO) and low-temperature tetragonal (LTT) crystal
symmetry. Within an explicit mean-field model it is shown how local LTT regions
act as pinning centers for static stripe formation. We calculate the
modulations in the local density of states near these local stripe regions and
find that mainly the coherence peaks and the van Hove singularity (VHS) are
spatially modulated. Lastly, we use the real-space approach to simulate recent
tunneling data in the overdoped regime where the VHS has been detected by
utilizing local normal state regions.Comment: Conference proceedings for Stripes1
Experimentally feasible quantum erasure-correcting code for continuous variables
We devise a scheme that protects quantum coherent states of light from
probabilistic losses, thus achieving the first continuous-variable quantum
erasure-correcting code. If the occurrence of erasures can be probed, then the
decoder enables, in principle, a perfect recovery of the original light states.
Otherwise, if supplemented with postselection based on homodyne detection, this
code can be turned into an efficient erasure-filtration scheme. The
experimental feasibility of the proposed protocol is carefully addressed
Origin of electronic dimers in the spin-density wave phase of Fe-based superconductors
We investigate the emergent impurity-induced states arising from point-like
scatterers in the spin-density wave phase of iron-based superconductors within
a microscopic five-band model. Independent of the details of the band-structure
and disorder potential, it is shown how stable magnetic (pi,pi) unidirectional
nematogens are formed locally by the impurities. Interestingly, these
nematogens exhibit a dimer structure in the electronic density, are directed
along the antiferromagnetic a-axis, and have typical lengths of order 10
lattice constants in excellent agreement with recent scanning tunnelling
experiments. These electronic dimers provide a natural explanation of the
dopant-induced transport anisotropy found e.g. in the 122 iron pnictides.Comment: 5 pages, 4 figure
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