1,271 research outputs found
SO(5) theory of insulating vortex cores in high- materials
We study the fermionic states of the antiferromagnetically ordered vortex
cores predicted to exist in the superconducting phase of the newly proposed
SO(5) model of strongly correlated electrons. Our model calculation gives a
natural explanation of the recent STM measurements on BSCCO, which in
surprising contrast to YBCO revealed completely insulating vortex cores.Comment: 4 pages, 1 figur
A Self-Consistent Microscopic Theory of Surface Superconductivity
The electronic structure of the superconducting surface sheath in a type-II
superconductor in magnetic fields is calculated
self-consistently using the Bogoliubov-de Gennes equations. We find that the
pair potential exhibits pronounced Friedel oscillations near the
surface, in marked contrast with the results of Ginzburg-Landau theory. The
role of magnetic edge states is emphasized. The local density of states near
the surface shows a significant depletion near the Fermi energy due to the
development of local superconducting order. We suggest that this structure
could be unveiled by scanning-tunneling microscopy studies performed near the
edge of a superconducting sample.Comment: 12 pages, Revtex 3.0, 3 postscript figures appende
Mercury in Our Environment
A project was initiated July 1, 1971, involving the Station Biochemistry and Animal Science departments, to study mercury from the standpoint of (1) methods for mercury determination in natural materials, (2) a survey of the occurrence of mercury in nature in South Dakota and (3) the toxicity of different chemical forms of mercury especially with respect to animal reproduction and teratogenic effects
Absence of Dipole Transitions in Vortices of Type II Superconductors
The response of a single vortex to a time dependent field is examined
microscopically and an equation of motion for vortex motion at non-zero
frequencies is derived. Of interest are frequencies near ,
where is the bulk energy gap and is the fermi energy. The low
temperature, clean, extreme type II limit and maintaining of equilibrium with
the lattice are assumed. A simplification occurs for large planar mass
anisotropy. Thus the results may be pertinent to materials such as and
high temperature superconductors. The expected dipole transition between core
states is hidden because of the self consistent nature of the vortex potential.
Instead the vortex itself moves and has a resonance at the frequency of the
transition.Comment: 12 pages, no figure
Quasiparticle States at a d-Wave Vortex Core in High-Tc Superconductors: Induction of Local Spin Density Wave Order
The local density of states (LDOS) at one of the vortex lattice cores in a
high Tc superconductor is studied by using a self-consistent mean field theory
including interactions for both antiferromagnetism (AF) and d-wave
superconductivity (DSC). The parameters are chosen in such a way that in an
optimally doped sample the AF order is completely suppressed while DSC
prevails. In the mixed state, we show that the local AF-like SDW order appears
near the vortex core and acts as an effective local magnetic field on the
quasiparticles. As a result, the LDOS at the core exhibits a double-peak
structure near the Fermi level that is in good agreement with the STM
observations on YBCO and BSCCO. The presence of local AF order near the votex
core is also consistent with the recent neutron scattering experiment on LSCO.Comment: 4 pages, 2 ps figure
Local density of states in the vortex lattice in a type II superconductor
Local density of states (LDOS) in the triangular vortex lattice is
investigated based on the quasi-classical Eilenberger theory. We consider the
case of an isotropic s-wave superconductor with the material parameter
appropriate to NbSe_2. At a weak magnetic field, the spatial variation of the
LDOS shows cylindrical structure around a vortex core. On the other hand, at a
high field where the core regions substantially overlap each other, the LDOS is
sixfold star-shaped structure due to the vortex lattice effect. The orientation
of the star coincides with the experimental data of the scanning tunneling
microscopy. That is, the ray of the star extends toward the nearest-neighbor
(next nearest-neighbor) vortex direction at higher (lower) energy.Comment: 10 pages, RevTex, 32 figure
Frequency dependent conductivity of vortex cores in type II superconductors
This paper is relevant to the recent optical transmission experiments of
Karrai et al. for vortices in high Tc superconductors. We begin with a
substantial review and introduction. The microscopic response of vortices is
calculated from the Bogoliubov-deGennes equation, including an equation of
motion and conductivity. We find that the expected resonant dipole transtition
is not present because of translation invariance. We consider the effect of
pinning and show that in the presence of pinning one recovers the dipole
resonance. Thus we conclude that pinning may play an important role in the
experiment.Comment: 35 pages plus six pages of figures: not included but postscript files
available upon request. Send requests and other comments to:
[email protected]. Revte
Mitotic regulators TPX2 and Aurora A protect DNA forks during replication stress by counteracting 53BP1 function
Arg/N-degron pathway targets transcription factors and regulates specific genes
The Arg/N-degron pathway targets proteins for degradation by recognizing their N-terminal or internal degrons. Our previous work produced double-knockout (2-KO) HEK293T human cell lines that lacked the functionally overlapping UBR1 and UBR2 E3 ubiquitin ligases of the Arg/N-degron pathway. Here, we studied these cells in conjunction with RNA-sequencing, mass spectrometry (MS), and split-ubiquitin binding assays. 1) Some mRNAs, such as those encoding lactate transporter MCT2 and β-adrenergic receptor ADRB2, are strongly (∼20-fold) up-regulated in 2-KO cells, whereas other mRNAs, including those encoding MAGEA6 (a regulator of ubiquitin ligases) and LCP1 (an actin-binding protein), are completely repressed in 2-KO cells, in contrast to wild-type cells. 2) Glucocorticoid receptor (GR), an immunity-modulating transcription factor (TF), is up-regulated in 2-KO cells and also physically binds to UBR1, strongly suggesting that GR is a physiological substrate of the Arg/N-degron pathway. 3) PREP1, another TF, was also found to bind to UBR1. 4) MS-based analyses identified ∼160 proteins whose levels were increased or decreased by more than 2-fold in 2-KO cells. For example, the homeodomain TF DACH1 and the neurofilament subunits NF-L (NFEL) and NF-M (NFEM) were expressed in wild-type cells but were virtually absent in 2-KO cells. 5) The disappearance of some proteins in 2-KO cells took place despite up-regulation of their mRNAs, strongly suggesting that the Arg/N-degron pathway can also modulate translation of specific mRNAs. In sum, this multifunctional proteolytic system has emerged as a regulator of mammalian gene expression, in part through conditional targeting of TFs that include ATF3, GR, and PREP1
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