1,032 research outputs found
Nuclear spin-lattice relaxation time in TaP and the Knight shift of Weyl semimetals
We first analyze the recent experimental data on the nuclear spin-lattice
relaxation rate of the Weyl semimetal TaP. We argue that its non-monotonic
temperature dependence is explained by the temperature dependent chemical
potential of Weyl fermions. We also develop the theory of the Knight shift in
Weyl semimetals, which contains two counteracting terms. The diamagnetic term
follows with , and being the high
energy cutoff, chemical potential and temperature, respectively, and is always
negative. The paramagnetic term scales with and changes sign depending on
the doping level. Altogether, the Knight shift is predicted to vanish or even
change sign upon changing the doping or the temperature, making it a sensitive
tool to identify Weyl points. We also calculate the Korringa relation for Weyl
semimetals which shows an unusual energy dependence rather than being constant
as expected for a non-interacting Fermi system.Comment: 9 pages, 3 figure
The Membrane-Associated Adaptor Protein DOK5 Is Upregulated in Systemic Sclerosis and Associated with IGFBP-5-Induced Fibrosis
Systemic sclerosis (SSc) is characterized by excessive fibrosis of the skin and internal organs due to fibroblast proliferation and excessive production of extracellular matrix (ECM). We have shown that insulin-like growth factor binding protein (IGFBP)-5 plays an important role in the development of fibrosis in vitro, ex vivo, and in vivo. We identified a membrane-associated adaptor protein, downstream of tyrosine kinase/docking protein (DOK)5, as an IGFBP-5-regulated target gene using gene expression profiling of primary fibroblasts expressing IGFBP-5. DOK5 is a tyrosine kinase substrate associated with intracellular signaling. Our objective was to determine the role of DOK5 in the pathogenesis of SSc and specifically in IGFBP-5-induced fibrosis. DOK5 mRNA and protein levels were increased in vitro by endogenous and exogenous IGFBP-5 in primary human fibroblasts. DOK5 upregulation required activation of the mitogen-activated protein kinase (MAPK) signaling cascade. Further, IGFBP-5 triggered nuclear translocation of DOK5. DOK5 protein levels were also increased in vivo in mouse skin and lung by IGFBP-5. To determine the effect of DOK5 on fibrosis, DOK5 was expressed ex vivo in human skin in organ culture. Expression of DOK5 in human skin resulted in a significant increase in dermal thickness. Lastly, levels of DOK5 were compared in primary fibroblasts and lung tissues of patients with SSc and healthy donors. Both DOK5 mRNA and protein levels were significantly increased in fibroblasts and skin tissues of patients with SSc compared with those of healthy controls, as well as in lung tissues of SSc patients. Our findings suggest that IGFBP-5 induces its pro-fibrotic effects, at least in part, via DOK5. Furthermore, IGFBP-5 and DOK5 are both increased in SSc fibroblasts and tissues and may thus be acting in concert to promote fibrosis
Coexistence of double-Q spin density wave and multi-Q pair density wave in cuprate oxide superconductors
Spatial 4a x 4a modulations, with a the lattice constant of CuO_2 planes, or
the so called checkerboards can arise from double-Q spin density wave (SDW)
with Q_1 = (pm pi/a, pm 3 pi/4a) and Q_2 = (pm 3 pi/4a, pm pi/a). When multi-Q
pair density wave, that is, the condensation of d gamma-wave Cooper pairs with
zero total momenta, pm 2Q_1, pm 2Q_2, pm 4Q_1, pm 4Q_2, and so on is induced by
the SDW, gaps can have fine structures similar to those of the so called
zero-temperature pseudogaps.Comment: 4 pages, 3 figure
On the origin of the hump structure in the in-plane optical conductivity of high Tc cuprates based on a SU(2) slave-boson theory
An improved version of SU(2) slave-boson approach is applied to study the
in-plane optical conductivity of the two dimensional systems of high Tc
cuprates. We investigate the role of fluctuations of both the phase and
amplitude of order parameters on the (Drude) peak-dip-hump structure in the
in-plane conductivity as a function of hole doping concentration and
temperature. The mid-infrared(MIR) hump in the in-plane optical conductivity is
shown to originate from the antiferromagnetic spin fluctuations of short
range(the amplitude fluctuations of spin singlet pairing order parameters),
which is consistent with our previous U(1) study. However the inclusion of both
the phase and amplitude fluctuations is shown to substantially improve the
qualitative feature of the optical conductivity by showing substantially
reduced Drude peak widths for entire doping range. Both the shift of the hump
position to lower frequency and the growth of the hump peak height with
increasing hole concentration is shown to be consistent with observations.Comment: 7 pages, 6 figure
Hyperfine Interactions in the Heavy Fermion CeMIn_5 Systems
The CeMIn_5 heavy fermion compounds have attracted enormous interest since
their discovery six years ago. These materials exhibit a rich spectrum of
unusual correlated electron behavior, and may be an ideal model for the high
temperature superconductors. As many of these systems are either
antiferromagnets, or lie close to an antiferromagnetic phase boundary, it is
crucial to understand the behavior of the dynamic and static magnetism. Since
neutron scattering is difficult in these materials, often the primary source of
information about the magnetic fluctuations is Nuclear Magnetic Resonance
(NMR). Therefore, it is crucial to have a detailed understanding of how the
nuclear moments interact with conduction electrons and the local moments
present in these systems. Here we present a detailed analysis of the hyperfine
coupling based on anisotropic hyperfine coupling tensors between nuclear
moments and local moments. Because the couplings are symmetric with respect to
bond axes rather than crystal lattice directions, the nuclear sites can
experience non-vanishing hyperfine fields even in high symmetry sites.Comment: 15 pages, 5 figure
Anisotropic Ru3+ 4d5 magnetism in the alpha-RuCl3 honeycomb system: susceptibility, specific heat and Zero field NMR
Hexagonal alpha-Ru trichloride single crystals exhibit a strong magnetic
anisotropy and we show that upon applying fields up to 14 T in the honeycomb
plane the successive magnetic order at T1 = 14 K and T2 = 8 K could be
completely suppressed whereas in the perpendicular direction the magnetic order
is robust. Furthermore the field dependence of chi(T) implies coexisting ferro-
and antiferromagnetic exchange between in-plane components of Ru^3+-spins,
whereas for out-of-plane components a strong antiferromagnetic exchange becomes
evident. 101^Ru zero-field nuclear magnetic resonance in the ordered state
evidence a complex (probably non coplanar chiral) long-range magnetic
structure. The large orbital moment on Ru^3+ is found in density-functional
calculations.Comment: 5 pages and 4 figure
Competing magnetic correlations across the ferromagnetic quantum critical point in the Kondo system CeTiVGe: V NMR as a local probe
V nuclear magnetic resonance (NMR) and magnetization studies on
CeTiVGe have been performed to explore the evolution from the
ferromagnetic () to the antiferromagnetic Kondo lattice state (), with focus on the emergence of a possible ferromagnetic quantum critical
point (FMQCP) at . From the temperature dependence of the
nuclear spin-lattice relaxation rate, , and the Knight shift,
\textit{K}, for and a considerable competition between ferro-
and antiferromagnetic correlations is found. Around the critical concentration
() quantum-critical spin fluctuations entail weak
antiferromagnetic spin fluctuations admixed with ferromagnetic spin
fluctuations. The FMQCP in CeTiVGe therefore is not purely
ferromagnetic in nature.Comment: 9 pages and 12 figures, accepted at PR
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