281 research outputs found
Driving magnetic order in a manganite by ultrafast lattice excitation
Optical control of magnetism, of interest for high-speed data processing and
storage, has only been demonstrated with near-infrared excitation to date.
However, in absorbing materials, such high photon energies can lead to
significant dissipation, making switch back times long and miniaturization
challenging. In manganites, magnetism is directly coupled to the lattice, as
evidenced by the response to external and chemical pressure, or to
ferroelectric polarization. Here, femtosecond mid-infrared pulses are used to
excite the lattice in La0.5Sr1.5MnO4 and the dynamics of electronic order are
measured by femtosecond resonant soft x-ray scattering with an x-ray free
electron laser. We observe that magnetic and orbital orders are reduced by
excitation of the lattice. This process, which occurs within few picoseconds,
is interpreted as relaxation of the complex charge-orbital-spin structure
following a displacive exchange quench - a prompt shift in the equilibrium
value of the magnetic and orbital order parameters after the lattice has been
distorted. A microscopic picture of the underlying unidirectional lattice
displacement is proposed, based on nonlinear rectification of the
directly-excited vibrational field, as analyzed in the specific lattice
symmetry of La0.5Sr1.5MnO4. Control of magnetism through ultrafast lattice
excitation has important analogies to the multiferroic effect and may serve as
a new paradigm for high-speed optomagnetism.Comment: 10 pages manuscript, 4 figure
Ultrafast Laser-Induced Melting of Long-Range Magnetic Order in Multiferroic TbMnO3
We performed ultrafast time-resolved near-infrared pump, resonant soft X-ray
diffraction probe measurements to investigate the coupling between the
photoexcited electronic system and the spin cycloid magnetic order in
multiferroic TbMnO3 at low temperatures. We observe melting of the long range
antiferromagnetic order at low excitation fluences with a decay time constant
of 22.3 +- 1.1 ps, which is much slower than the ~1 ps melting times previously
observed in other systems. To explain the data we propose a simple model of the
melting process where the pump laser pulse directly excites the electronic
system, which then leads to an increase in the effective temperature of the
spin system via a slower relaxation mechanism. Despite this apparent increase
in the effective spin temperature, we do not observe changes in the wavevector
q of the antiferromagnetic spin order that would typically correlate with an
increase in temperature under equilibrium conditions. We suggest that this
behavior results from the extremely low magnon group velocity that hinders a
change in the spin-spiral wavevector on these time scales.Comment: 9 pages, 4 figure
BCAT1 redox function maintains mitotic fidelity
The metabolic enzyme branched-chain amino acid transaminase 1 (BCAT1) drives cell proliferation in aggressive cancers such as glioblastoma. Here, we show that BCAT1 localizes to mitotic structures and has a non-metabolic function as a mitotic regulator. Furthermore, BCAT1 is required for chromosome segregation in cancer and induced pluripotent stem cells and tumor growth in human cerebral organoid and mouse syngraft models. Applying gene knockout and rescue strategies, we show that the BCAT1 CXXC redox motif is crucial for controlling cysteine sulfenylation specifically in mitotic cells, promoting Aurora kinase B localization to centromeres, and securing accurate chromosome segregation. These findings offer an explanation for the well-established role of BCAT1 in promoting cancer cell proliferation. In summary, our data establish BCAT1 as a component of the mitotic apparatus that safeguards mitotic fidelity through a moonlighting redox functionality
XFEL resonant photo-pumping of dense plasmas and dynamic evolution of autoionizing core hole states
Probing the interplay between lattice dynamics and short-range magnetic correlations in CuGeO3 with femtosecond RIXS
Investigations of magnetically ordered phases on the femtosecond timescale
have provided significant insights into the influence of charge and lattice
degrees of freedom on the magnetic sub-system. However, short-range magnetic
correlations occurring in the absence of long-range order, for example in
spin-frustrated systems, are inaccessible to many ultrafast techniques. Here,
we show how time-resolved resonant inelastic X-ray scattering (trRIXS) is
capable of probing such short-ranged magnetic dynamics in a charge-transfer
insulator through the detection of a Zhang-Rice singlet exciton. Utilizing
trRIXS measurements at the O K-edge, and in combination with model
calculations, we probe the short-range spin-correlations in the frustrated spin
chain material CuGeO3 following photo-excitation, revealing a strong coupling
between the local lattice and spin sub-systems
Alien Registration- Breton, Honore (Lewiston, Androscoggin County)
https://digitalmaine.com/alien_docs/30621/thumbnail.jp
Spatially resolved ultrafast magnetic dynamics launched at a complex-oxide hetero-interface
Static strain in complex oxide heterostructures has been extensively used to engineer electronic and magnetic properties at equilibrium. In the same spirit, deformations of the crystal lattice with light may be used to achieve functional control across hetero-interfaces dynamically. Here, by exciting large amplitude infrared-active vibrations in a LaAlO3 substrate we induce magnetic order melting in a NdNiO3 film across a hetero-interface. Femtosecond Resonant Soft X-ray Diffraction is used to determine the spatial and temporal evolution of the magnetic disordering. We observe a magnetic melt front that grows from the substrate interface into the film, at a speed that suggests electronically driven propagation. Light control and ultrafast phase front propagation at hetero-interfaces may lead to new opportunities in optomagnetism, for example by driving domain wall motion to transport information across suitably designed devices
Spatially resolved ultrafast magnetic dynamics launched at a complex-oxide hetero-interface
Static strain in complex oxide heterostructures has been extensively used to
engineer electronic and magnetic properties at equilibrium. In the same spirit,
deformations of the crystal lattice with light may be used to achieve
functional control across hetero-interfaces dynamically. Here, by exciting
large amplitude infrared-active vibrations in a LaAlO3 substrate we induce
magnetic order melting in a NdNiO3 film across a hetero-interface. Femtosecond
Resonant Soft X-ray Diffraction is used to determine the spatial and temporal
evolution of the magnetic disordering. We observe a magnetic melt front that
grows from the substrate interface into the film, at a speed that suggests
electronically driven propagation. Light control and ultrafast phase front
propagation at hetero-interfaces may lead to new opportunities in
optomagnetism, for example by driving domain wall motion to transport
information across suitably designed devices.Comment: 35 pages, 8 Figures (both incl. Supplement
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