3,825 research outputs found
Weak Mott insulators on the triangular lattice: possibility of a gapless nematic quantum spin liquid
We study the energetics of Gutzwiller projected BCS states of various
symmetries for the triangular lattice antiferromagnet with a four particle ring
exchange using variational Monte Carlo methods. In a range of parameters the
energetically favored state is found to be a projected paired
state which breaks lattice rotational symmetry. We show that the properties of
this nematic or orientationally ordered paired spin liquid state as a function
of temperature and pressure can account for many of the experiments on organic
materials. We also study the ring-exchange model with ferromagnetic Heisenberg
exchange and find that amongst the studied ans\"atze, a projected wave
state is the most favorable.Comment: Longer version, 7+ pages, 5 figure
Scattering quantum random-walk search with errors
We analyze the realization of a quantum-walk search algorithm in a passive,
linear optical network. The specific model enables us to consider the effect of
realistic sources of noise and losses on the search efficiency. Photon loss
uniform in all directions is shown to lead to the rescaling of search time.
Deviation from directional uniformity leads to the enhancement of the search
efficiency compared to uniform loss with the same average. In certain cases
even increasing loss in some of the directions can improve search efficiency.
We show that while we approach the classical limit of the general search
algorithm by introducing random phase fluctuations, its utility for searching
is lost. Using numerical methods, we found that for static phase errors the
averaged search efficiency displays a damped oscillatory behaviour that
asymptotically tends to a non-zero value.Comment: 10 pages, 10 figures. Two figures added for clarity, also made
improvements to the tex
Vortex Phase Diagram of weakly pinned YBaCuO for H c
Vortex phase diagram in a weakly pinned crystal of YBCO for H c
is reviewed in the light of a recent elucidation of the process of `inverse
melting' in a Bismuth cuprate system and the imaging of an interface between
the ordered and the disordered regions across the peak effect in 2H-NbSe.
In the given YBCO crystal, a clear distinction can be made between the second
magnetization peak (SMP) and the peak effect (PE) between 65 K and 75 K. The
field region between the peak fields of the SMP (H) and the onset
fields of the PE (H)is not only continuously connected to the Bragg
glass phase at lower fields but it is also sandwiched between the higher
temperature vortex liquid phase and the lower temperature vortex glass phase.
Thus, an ordered vortex state between H and H can get
transformed to the (disordered) vortex liquid state on heating as well as to
the (disordered) vortex glass state on cooling, a situation analogous to the
thermal melting and the inverse melting phenomenon seen in a Bismuth cuprate.Comment: Presented in IWCC-200
Comparison of Gravitational Wave Detector Network Sky Localization Approximations
Gravitational waves emitted during compact binary coalescences are a
promising source for gravitational-wave detector networks. The accuracy with
which the location of the source on the sky can be inferred from gravitational
wave data is a limiting factor for several potential scientific goals of
gravitational-wave astronomy, including multi-messenger observations. Various
methods have been used to estimate the ability of a proposed network to
localize sources. Here we compare two techniques for predicting the uncertainty
of sky localization -- timing triangulation and the Fisher information matrix
approximations -- with Bayesian inference on the full, coherent data set. We
find that timing triangulation alone tends to over-estimate the uncertainty in
sky localization by a median factor of for a set of signals from
non-spinning compact object binaries ranging up to a total mass of , and the over-estimation increases with the mass of the system. We
find that average predictions can be brought to better agreement by the
inclusion of phase consistency information in timing-triangulation techniques.
However, even after corrections, these techniques can yield significantly
different results to the full analysis on specific mock signals. Thus, while
the approximate techniques may be useful in providing rapid, large scale
estimates of network localization capability, the fully coherent Bayesian
analysis gives more robust results for individual signals, particularly in the
presence of detector noise.Comment: 11 pages, 7 Figure
Reframing commitment in authentic leadership: Untangling relationship–outcome processes
Affective organizational commitment is theorized and empirically tested as a key mediator between authentic leadership and desirable employee outcomes. The results of a two-wave survey of 830 business people in Australia support a serial mediation model of authentic leadership efficacy. Followers\u27 perceptions of authentic leadership behavior influence their personal identification and affect-based trust in the leader, which in turn are mediated by affective organizational commitment to positively influence their work engagement and job satisfaction. These findings reinforce previous work that positions personal identification and affect-based trust as the two primary mediating mechanisms of authentic leadership. This paper extends prior research by demonstrating the important role of followers\u27 affective bonds with their organization in the operation of authentic leadership, moving beyond the dyad in our understanding of follower outcomes
Reframing commitment in authentic leadership: Untangling relationship–outcome processes
Affective organizational commitment is theorized and empirically tested as a key mediator between authentic leadership and desirable employee outcomes. The results of a two-wave survey of 830 business people in Australia support a serial mediation model of authentic leadership efficacy. Followers\u27 perceptions of authentic leadership behavior influence their personal identification and affect-based trust in the leader, which in turn are mediated by affective organizational commitment to positively influence their work engagement and job satisfaction. These findings reinforce previous work that positions personal identification and affect-based trust as the two primary mediating mechanisms of authentic leadership. This paper extends prior research by demonstrating the important role of followers\u27 affective bonds with their organization in the operation of authentic leadership, moving beyond the dyad in our understanding of follower outcomes
New Samarium and Neodymium based admixed ferromagnets with near zero net magnetization and tunable exchange bias field
Rare earth based intermetallics, SmScGe and NdScGe, are shown to exhibit near
zero net magnetization with substitutions of 6 to 9 atomic percent of Nd and 25
atomic percent of Gd, respectively. The notion of magnetic compensation in them
is also elucidated by the crossover of zero magnetization axis at low magnetic
fields (less than 103 Oe) and field-induced reversal in the orientation of the
magnetic moments of the dissimilar rare earth ions at higher magnetic fields.
These magnetically ordered materials with no net magnetization and appreciable
conduction electron polarization display an attribute of an exchange bias
field, which can be tuned. The attractively high magnetic ordering temperatures
of about 270 K, underscore the importance of these materials for potential
applications in spintronics.Comment: 6 page text + 5 figure
Probing the chiral anomaly with nonlocal transport in three dimensional topological semimetals
Weyl semimetals are three-dimensional crystalline systems where pairs of
bands touch at points in momentum space, termed Weyl nodes, that are
characterized by a definite topological charge: the chirality. Consequently,
they exhibit the Adler-Bell-Jackiw anomaly, which in this condensed matter
realization implies that application of parallel electric () and
magnetic () fields pumps electrons between nodes of opposite
chirality at a rate proportional to . We argue that
this pumping is measurable via nonlocal transport experiments, in the limit of
weak internode scattering. Specifically, we show that as a consequence of the
anomaly, applying a local magnetic field parallel to an injected current
induces a valley imbalance that diffuses over long distances. A probe magnetic
field can then convert this imbalance into a measurable voltage drop far from
source and drain. Such nonlocal transport vanishes when the injected current
and magnetic field are orthogonal, and therefore serves as a test of the chiral
anomaly. We further demonstrate that a similar effect should also characterize
Dirac semimetals --- recently reported to have been observed in experiments ---
where a pair of Weyl nodes coexisting at a single point in the Brillouin zone
are protected by a crystal symmetry. Since the nodes are analogous to valley
degrees of freedom in semiconductors, this suggests that valley currents in
three dimensional topological semimetals can be controlled using electric
fields, which has potential practical `valleytronic' applications.Comment: 10 pages, 5 figures; substantial revisions include applications to
Dirac semimetals and a treatment of impurity scattering and imbalance
relaxation. Version accepted in Phys. Rev.
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