132 research outputs found
Entanglement Entropy with Lifshitz Fermions
We investigate fermions with Lifshitz scaling symmetry and study their
entanglement entropy in 1+1 dimensions as a function of the scaling exponent
. Remarkably, in the ground state the entanglement entropy vanishes for even
values of , whereas for odd values it is independent of and equal to the
relativistic case with . We show this using the correlation method on the
lattice, and also using a holographic cMERA approach. The entanglement entropy
in a thermal state is a more detailed function of and which we plot
using the lattice correlation method. The dependence on the even- or oddness of
still shows for small temperatures, but is washed out for large
temperatures or large values of .Comment: 19 pages, 4 figure
Spin-accumulation induced magnetic texture in a metal-insulator bilayer
We consider the influence of a spin accumulation in a normal metal on the
magnetic statics and dynamics in an adjacent magnetic insulator. In particular,
we focus on arbitary angles between the spin accumulation and the easy-axis of
the magnetic insulator. Based on Landau-Lifshitz-Gilbert phenomenology
supplemented with magnetoelectronic circuit theory, we find that the magnetic
texture twists into a stable configuration that turns out to be described by a
virtual, or image, domain wall configuration, i.e., a domain wall outside the
ferromagnet. We show that even when the spin accumulation is perpendicular to
the anisotropy axis, the magnetic texture develops a component parallel to the
spin accumulation for sufficiently large spin bias. The emergence of this
parallel component gives rise to threshold behavior in the spin Hall
magnetoresistance and nonlocal magnon transport. This threshold can be used to
design novel spintronic and magnonic devices that can be operated without
external magnetic fields.Comment: 11 pages, 5 figures, including appendice
Asymmetric magnetic bubble expansion under in-plane field in Pt/Co/Pt: effect of interface engineering
We analyse the impact of growth conditions on asymmetric magnetic bubble
expansion under in-plane field in ultrathin Pt / Co / Pt films. Specifically,
using sputter deposition we vary the Ar pressure during the growth of the top
Pt layer. This induces a large change in the interfacial structure as evidenced
by a factor three change in the effective perpendicular magnetic anisotropy.
Strikingly, a discrepancy between the current theory for domain-wall
propagation based on a simple domain-wall energy density and our experimental
results is found. This calls for further theoretical development of domain-wall
creep under in-plane fields and varying structural asymmetry.Comment: 16 pages, 3 figure
Electrically switchable entanglement channel in van der Waals magnets
Two-dimensional layered van der Waals (vdW) magnets demonstrate their potential to allow the study
of both fundamental and applied physics due to their remarkable electronic properties. However, the connection of vdW magnets to spintronics and quantum information science is not clear. In particular, it
remains elusive whether there are interesting magnetic phenomena belonging only to vdW magnets but
absent in widely studied crystalline magnets. Here, we consider the quantum correlations of magnons
in a layered vdW magnet and identify an entanglement channel of magnons across the magnetic layers,
which can be effectively tuned and even deterministically switched on and off by both magnetic and electric means. This is a unique feature of vdW magnets, in which the underlying physics is well understood
in terms of the competing roles of exchange and anisotropy fields that contribute to magnon excitation.
Furthermore, we show that such a tunable entanglement channel can mediate the electrically controllable
entanglement of two distant qubits, which also provides a protocol to indirectly measure the entanglement of magnons. Our findings provide an avenue to electrically manipulate qubits and further open up
opportunities to utilize vdW magnets for quantum information scienc
Creep of Chiral Domain Walls
Recent experimental studies of magnetic domain expansion under easy-axis
drive fields in materials with a perpendicular magnetic anisotropy have shown
that the domain wall velocity is asymmetric as a function of an external in
plane magnetic field. This is understood as a consequence of the inversion
asymmetry of the system, yielding a finite chiral Dzyaloshinskii-Moriya
interaction. Numerous attempts have been made to explain these observations
using creep theory, but, in doing so, these have not included all contributions
to the domain wall energy or have introduced additional free parameters. In
this article we present a theory for creep motion of chiral domain walls in the
creep regime that includes the most important contributions to the domain-wall
energy and does not introduce new free parameters beyond the usual parameters
that are included in the micromagnetic energy. Furthermore, we present
experimental measurements of domain wall velocities as a function of in-plane
field that are well decribed by our model, and from which material properties
such as the strength of the Dzyaloshinskii-Moriya interaction and the
demagnetization field are extracted.Comment: 6 pages, 4 figures, Supplemental Material (15 pages, 9 figures
Search for Higgs Bosons in e+e- Collisions at 183 GeV
The data collected by the OPAL experiment at sqrts=183 GeV were used to
search for Higgs bosons which are predicted by the Standard Model and various
extensions, such as general models with two Higgs field doublets and the
Minimal Supersymmetric Standard Model (MSSM). The data correspond to an
integrated luminosity of approximately 54pb-1. None of the searches for neutral
and charged Higgs bosons have revealed an excess of events beyond the expected
background. This negative outcome, in combination with similar results from
searches at lower energies, leads to new limits for the Higgs boson masses and
other model parameters. In particular, the 95% confidence level lower limit for
the mass of the Standard Model Higgs boson is 88.3 GeV. Charged Higgs bosons
can be excluded for masses up to 59.5 GeV. In the MSSM, mh > 70.5 GeV and mA >
72.0 GeV are obtained for tan{beta}>1, no and maximal scalar top mixing and
soft SUSY-breaking masses of 1 TeV. The range 0.8 < tanb < 1.9 is excluded for
minimal scalar top mixing and m{top} < 175 GeV. More general scans of the MSSM
parameter space are also considered.Comment: 49 pages. LaTeX, including 33 eps figures, submitted to European
Physical Journal
A Measurement of the Product Branching Ratio f(b->Lambda_b).BR(Lambda_b->Lambda X) in Z0 Decays
The product branching ratio, f(b->Lambda_b).BR(Lambda_b->Lambda X), where
Lambda_b denotes any weakly-decaying b-baryon, has been measured using the OPAL
detector at LEP. Lambda_b are selected by the presence of energetic Lambda
particles in bottom events tagged by the presence of displaced secondary
vertices. A fit to the momenta of the Lambda particles separates signal from B
meson and fragmentation backgrounds. The measured product branching ratio is
f(b->Lambda_b).BR(Lambda_b->Lambda X) = (2.67+-0.38(stat)+0.67-0.60(sys))%
Combined with a previous OPAL measurement, one obtains
f(b->Lambda_b).BR(Lambda_b->Lambda X) = (3.50+-0.32(stat)+-0.35(sys))%.Comment: 16 pages, LaTeX, 3 eps figs included, submitted to the European
Physical Journal
Synaptic processes and immune-related pathways implicated in Tourette syndrome
Tourette syndrome (TS) is a neuropsychiatric disorder of complex genetic architecture involving multiple interacting genes. Here, we sought to elucidate the pathways that underlie the neurobiology of the disorder through genome-wide analysis. We analyzed genome-wide genotypic data of 3581 individuals with TS and 7682 ancestry-matched controls and investigated associations of TS with sets of genes that are expressed in particular cell types and operate in specific neuronal and glial functions. We employed a self-contained, set-based association method (SBA) as well as a competitive gene set method (MAGMA) using individual-level genotype data to perform a comprehensive investigation of the biological background of TS. Our SBA analysis identified three significant gene sets after Bonferroni correction, implicating ligand-gated ion channel signaling, lymphocytic, and cell adhesion and transsynaptic signaling processes. MAGMA analysis further supported the involvement of the cell adhesion and trans-synaptic signaling gene set. The lymphocytic gene set was driven by variants in FLT3, raising an intriguing hypothesis for the involvement of a neuroinflammatory element in TS pathogenesis. The indications of involvement of ligand-gated ion channel signaling reinforce the role of GABA in TS, while the association of cell adhesion and trans-synaptic signaling gene set provides additional support for the role of adhesion molecules in neuropsychiatric disorders. This study reinforces previous findings but also provides new insights into the neurobiology of TS
Synaptic processes and immune-related pathways implicated in Tourette syndrome.
Tourette syndrome (TS) is a neuropsychiatric disorder of complex genetic architecture involving multiple interacting genes. Here, we sought to elucidate the pathways that underlie the neurobiology of the disorder through genome-wide analysis. We analyzed genome-wide genotypic data of 3581 individuals with TS and 7682 ancestry-matched controls and investigated associations of TS with sets of genes that are expressed in particular cell types and operate in specific neuronal and glial functions. We employed a self-contained, set-based association method (SBA) as well as a competitive gene set method (MAGMA) using individual-level genotype data to perform a comprehensive investigation of the biological background of TS. Our SBA analysis identified three significant gene sets after Bonferroni correction, implicating ligand-gated ion channel signaling, lymphocytic, and cell adhesion and transsynaptic signaling processes. MAGMA analysis further supported the involvement of the cell adhesion and trans-synaptic signaling gene set. The lymphocytic gene set was driven by variants in FLT3, raising an intriguing hypothesis for the involvement of a neuroinflammatory element in TS pathogenesis. The indications of involvement of ligand-gated ion channel signaling reinforce the role of GABA in TS, while the association of cell adhesion and trans-synaptic signaling gene set provides additional support for the role of adhesion molecules in neuropsychiatric disorders. This study reinforces previous findings but also provides new insights into the neurobiology of TS
Synaptic processes and immune-related pathways implicated in Tourette syndrome
Tourette syndrome (TS) is a neuropsychiatric disorder of complex genetic architecture involving multiple interacting genes. Here, we sought to elucidate the pathways that underlie the neurobiology of the disorder through genome-wide analysis. We analyzed genome-wide genotypic data of 3581 individuals with TS and 7682 ancestry-matched controls and investigated associations of TS with sets of genes that are expressed in particular cell types and operate in specific neuronal and glial functions. We employed a self-contained, set-based association method (SBA) as well as a competitive gene set method (MAGMA) using individual-level genotype data to perform a comprehensive investigation of the biological background of TS. Our SBA analysis identified three significant gene sets after Bonferroni correction, implicating ligand-gated ion channel signaling, lymphocytic, and cell adhesion and transsynaptic signaling processes. MAGMA analysis further supported the involvement of the cell adhesion and trans-synaptic signaling gene set. The lymphocytic gene set was driven by variants in FLT3, raising an intriguing hypothesis for the involvement of a neuroinflammatory element in TS pathogenesis. The indications of involvement of ligand-gated ion channel signaling reinforce the role of GABA in TS, while the association of cell adhesion and trans-synaptic signaling gene set provides additional support for the role of adhesion molecules in neuropsychiatric disorders. This study reinforces previous findings but also provides new insights into the neurobiology of TS
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