507 research outputs found
Molecular Response in One-Photon Absorption via Natural Thermal Light vs Pulsed Laser Excitation
Photoinduced biological processes occur via one photon absorption in natural
light, which is weak, CW and incoherent, but are often studied in the
laboratory using pulsed coherent light. Here we compare the response of a
molecule to these two very different sources within a quantized radiation field
picture. The latter is shown to induce coherent time evolution in the molecule,
whereas the former does not. As a result, the coherent time dependence observed
in the laboratory experiments will not be relevant to the natural biological
process. Emphasis is placed on resolving confusions regarding this issue that
are shown to arise from aspects of quantum measurement and from a lack of
appreciation of the proper description of the absorbed photon.Comment: Revised (now published) manuscript: Replaces ArXiv:1109.002
Selective interlayer ferromagnetic coupling between the Cu spins in YBa Cu O grown on top of La Ca MnO
Studies to date on ferromagnet/d-wave superconductor heterostructures focus
mainly on the effects at or near the interfaces while the response of bulk
properties to heterostructuring is overlooked. Here we use resonant soft x-ray
scattering spectroscopy to reveal a novel c-axis ferromagnetic coupling between
the in-plane Cu spins in YBa Cu O (YBCO) superconductor when it
is grown on top of ferromagnetic La Ca MnO (LCMO) manganite
layer. This coupling, present in both normal and superconducting states of
YBCO, is sensitive to the interfacial termination such that it is only observed
in bilayers with MnO_2but not with La Ca interfacial
termination. Such contrasting behaviors, we propose, are due to distinct
energetic of CuO chain and CuO plane at the La Ca and
MnO terminated interfaces respectively, therefore influencing the transfer
of spin-polarized electrons from manganite to cuprate differently. Our findings
suggest that the superconducting/ferromagnetic bilayers with proper interfacial
engineering can be good candidates for searching the theorized
Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) state in cuprates and studying the
competing quantum orders in highly correlated electron systems.Comment: Please note the change of the title. Text might be slightly different
from the published versio
Probing impulsive strain propagation with x-ray pulses
Pump-probe time-resolved x-ray diffraction of allowed and nearly forbidden
reflections in InSb is used to follow the propagation of a coherent acoustic
pulse generated by ultrafast laser-excitation. The surface and bulk components
of the strain could be simultaneously measured due to the large x-ray
penetration depth. Comparison of the experimental data with dynamical
diffraction simulations suggests that the conventional model for impulsively
generated strain underestimates the partitioning of energy into coherent modes.Comment: 4 pages, 2 figures, LaTeX, eps. Accepted for publication in Phys.
Rev. Lett. http://prl.aps.or
Self-energy of image states on copper surfaces
We report extensive calculations of the imaginary part of the electron
self-energy in the vicinity of the (100) and (111) surfaces of Cu. The
quasiparticle self-energy is computed by going beyond a free-electron
description of the metal surface, either within the GW approximation of
many-body theory or with inclusion, within the GW approximation, of
short-range exchange-correlation effects. Calculations of the decay rate of the
first three image states on Cu(100) and the first image state on Cu(111) are
also reported, and the impact of both band structure and many-body effects on
the electron relaxation process is discussed.Comment: 8 pages, 5 figures, to appear in Phys. Rev.
Ferromagnetic Enhancement of CE-type Spin Ordering in (Pr,Ca)MnO
We present resonant soft X-ray scattering (RSXS) results from small band
width manganites (Pr,Ca)MnO, which show that the CE-type spin ordering (SO)
at the phase boundary is stabilized only below the canted antiferromagnetic
transition temperature and enhanced by ferromagnetism in the macroscopically
insulating state (FM-I). Our results reveal the fragility of the CE-type
ordering that underpins the colossal magnetoresistance (CMR) effect in this
system, as well as an unexpected cooperative interplay between FM-I and CE-type
SO which is in contrast to the competitive interplay between the ferromagnetic
metallic (FM-M) state and CE-type ordering.Comment: Accepted for publication in Phys. Rev. Let
Disruption of Immune Homeostasis in Human Dendritic Cells via Regulation of Autophagy and Apoptosis by
As fundamental processes of immune homeostasis, autophagy, and apoptosis must be maintained to mitigate risk of chronic inflammation and autoimmune diseases. Periodontitis is a chronic inflammatory disease characterized by oral microbial dysbiosis, and dysregulation of dendritic cell (DC) and T cell responses. The aim of this study was to elucidate the underlying mechanisms by which the oral microb
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