42,597 research outputs found
Inelastic neutron scattering signal from deconfined spinons in a fractionalized antiferromagnet
We calculate the contribution of deconfined spinons to inelastic neutron
scattering (INS) in the fractionalized antiferromagnet (AF*), introduced
elsewhere. We find that the presence of free spin-1/2 charge-less excitations
leads to a continuum INS signal above the Neel gap. This signal is found above
and in addition to the usual spin-1 magnon signal, which to lowest order is the
same as in the more conventional confined antiferromagnet. We calculate the
relative weights of these two signals and find that the spinons contribute to
the longitudinal response, where the magnon signal is absent to lowest order.
Possible higher-order effects of interactions between magnons and spinons in
the AF* phase are also discussed.Comment: 9 page
Robust non-adiabatic molecular dynamics for metals and insulators
We present a new formulation of the correlated electron-ion dynamics (CEID)
scheme, which systematically improves Ehrenfest dynamics by including quantum
fluctuations around the mean-field atomic trajectories. We show that the method
can simulate models of non-adiabatic electronic transitions, and test it
against exact integration of the time-dependent Schroedinger equation. Unlike
previous formulations of CEID, the accuracy of this scheme depends on a single
tunable parameter which sets the level of atomic fluctuations included. The
convergence to the exact dynamics by increasing the tunable parameter is
demonstrated for a model two level system. This algorithm provides a smooth
description of the non-adiabatic electronic transitions which satisfies the
kinematic constraints (energy and momentum conservation) and preserves quantum
coherence. The applicability of this algorithm to more complex atomic systems
is discussed.Comment: 36 pages, 5 figures. Accepted for publication in Journal of Chemical
Physic
Atypical energy eigenstates in the Hubbard chain and quantum disentangled liquids
We investigate the implications of integrability for the existence of quantum
disentangled liquid (QDL) states in the half-filled one-dimensional Hubbard
model. We argue that there exist finite energy-density eigenstates that exhibit
QDL behaviour in the sense of J. Stat. Mech. P10010 (2014). These states are
atypical in the sense that their entropy density is smaller than that of
thermal states at the same energy density. Furthermore, we show that thermal
states in a particular temperature window exhibit a weaker form of the QDL
property, in agreement with recent results obtained by strong-coupling
expansion methods in arXiv:1611.02075. This article is part of the themed issue
`Breakdown of ergodicity in quantum systems: from solids to synthetics matter'.Comment: 11 pages, 3 figures. arXiv admin note: text overlap with
arXiv:1611.0207
New Wrinkles on an Old Model: Correlation Between Liquid Drop Parameters and Curvature Term
The relationship between the volume and surface energy coefficients in the
liquid drop A^{-1/3} expansion of nuclear masses is discussed. The volume and
surface coefficients in the liquid drop expansion share the same physical
origin and their physical connection is used to extend the expansion with a
curvature term. A possible generalization of the Wigner term is also suggested.
This connection between coefficients is used to fit the experimental nuclear
masses. The excellent fit obtained with a smaller number of parameters
validates the assumed physical connection.Comment: 6 pages, 2 figure
Thunderstorm hazards flight research: Storm hazards 1980 overview
A highly instrumented NASA F-106B aircraft, modified for the storm hazards mission and protected against direct lightning strikes, was used in conjunction with various ground based radar and lightning measurement systems to collect data during thunderstorm penetration flights. During 69 thunderstorm penetrations, there were 10 direct lightning strikes to the aircraft. No problems were encountered with any of the aircraft's systems as a result of the strikes and the research instrumentation performed as designed. Electromagnetic characteristics of nine strikes were recorded, and the results of other experiments confirm the theory that X-ray radiation and nitrous oxide gas are being produced by processes associated directly with thunderstorm electric fields and lightning discharges. A better understanding of aircraft lightning attachment mechanisms and strike zones is being accomplished by careful inspection, identification, and documentation of lightning attachment points and swept stroke paths following each strike to the aircraft
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