61 research outputs found
Correlation tuned cross-over between thermal and nonthermal states following ultrafast transient pumping
We examine electron-electron mediated relaxation following excitation of a
correlated system by an ultrafast electric field pump pulse. The results reveal
a dichotomy in the temporal evolution as one tunes through a Mott
metal-to-insulator transition: in the metallic regime relaxation can be
characterized by evolution toward a steady-state electronic distribution well
described by Fermi-Dirac statistics with an increased effective temperature;
however, in the insulating regime this quasithermal paradigm breaks down with
relaxation toward a nonthermal state with a more complicated electronic
distribution that does not vary monotonically as a function of energy. We
characterize the behavior by studying changes in the energy, photoemission
response, and electronic distribution as functions of time. Qualitatively these
results should be observable on short enough time scales that the electrons
behave like an isolated system not in contact with additional degrees of
freedom which can act as a thermal bath. Importantly, proper modeling used to
analyze experimental findings should account for this behavior, especially when
using strong driving fields or studying materials whose physics may manifest
the effects of strong correlations.Comment: Main Text: 5 pages, 4 figures; Supplementary Material: 3 pages, 5
figure
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Casting of Gold Nanoparticles with High Aspect Ratios inside DNA Molds
DNA nanostructures provide a powerful platform for the programmable assembly of nanomaterials. Here this approach is extended to synthesize rod-like gold nanoparticles in a full DNA controlled manner. The approach is based on DNA molds containing elongated cavities. Gold is deposited inside the molds using a seeded-growth procedure. By carefully exploring the growth parameters it is shown that gold nanostructures with aspect ratios of up to 7 can be grown from single seeds. The highly anisotropic growth is in this case controlled only by the rather soft and porous DNA walls. The optimized seeded growth procedure provides a robust and simple routine to achieve continuous gold nanostructures using DNA templating
Overcoming challenges for CD3-bispecific antibody therapy in solid tumors
Simple SummaryCD3-bispecific antibody therapy is a form of immunotherapy that enables soldier cells of the immune system to recognize and kill tumor cells. This type of therapy is currently successfully used in the clinic to treat tumors in the blood and is under investigation for tumors in our organs. The treatment of these solid tumors faces more pronounced hurdles, which affect the safety and efficacy of CD3-bispecific antibody therapy. In this review, we provide a brief status update of this field and identify intrinsic hurdles for solid cancers. Furthermore, we describe potential solutions and combinatorial approaches to overcome these challenges in order to generate safer and more effective therapies.Immunotherapy of cancer with CD3-bispecific antibodies is an approved therapeutic option for some hematological malignancies and is under clinical investigation for solid cancers. However, the treatment of solid tumors faces more pronounced hurdles, such as increased on-target off-tumor toxicities, sparse T-cell infiltration and impaired T-cell quality due to the presence of an immunosuppressive tumor microenvironment, which affect the safety and limit efficacy of CD3-bispecific antibody therapy. In this review, we provide a brief status update of the CD3-bispecific antibody therapy field and identify intrinsic hurdles in solid cancers. Furthermore, we describe potential combinatorial approaches to overcome these challenges in order to generate selective and more effective responses.Experimental cancer immunology and therap
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Quantum fluctuations of charge order induce phonon softening in a superconducting cuprate
Quantum phase transitions play an important role in shaping the phase diagram
of high-temperature cuprate superconductors. These cuprates possess intertwined
orders which interact strongly with superconductivity. However, the evidence
for the quantum critical point associated with the charge order in the
superconducting phase remains elusive. Here we show the short-range charge
orders and the spectral signature of the quantum fluctuations in
LaSrCuO (LSCO) near the optimal doping using high-resolution
resonant inelastic X-ray scattering. On performing calculations through a
diagrammatic framework, we discovered that the charge correlations
significantly soften several branches of phonons. These results elucidate the
role of charge order in the LSCO compound, providing evidence for quantum
critical scaling and discommensurations associated with charge order
Quantum fluctuations of charge order induce phonon softening in a superconducting cuprate
Quantum phase transitions play an important role in shaping the phase diagram
of high-temperature cuprate superconductors. These cuprates possess intertwined
orders which interact strongly with superconductivity. However, the evidence
for the quantum critical point associated with the charge order in the
superconducting phase remains elusive. Here we show the short-range charge
orders and the spectral signature of the quantum fluctuations in
LaSrCuO (LSCO) near the optimal doping using high-resolution
resonant inelastic X-ray scattering. On performing calculations through a
diagrammatic framework, we discovered that the charge correlations
significantly soften several branches of phonons. These results elucidate the
role of charge order in the LSCO compound, providing evidence for quantum
critical scaling and discommensurations associated with charge order
Direct Optical Coupling to an Unoccupied Dirac Surface State in the Topological Insulator BiSe
We characterize the occupied and unoccupied electronic structure of the
topological insulator BiSe by one-photon and two-photon angle-resolved
photoemission spectroscopy and slab band structure calculations. We reveal a
second, unoccupied Dirac surface state with similar electronic structure and
physical origin to the well-known topological surface state. This state is
energetically located 1.5 eV above the conduction band, which permits it to be
directly excited by the output of a Ti:Sapphire laser. This discovery
demonstrates the feasibility of direct ultrafast optical coupling to a
topologically protected, spin-textured surface state.Comment: Accepted to Physical Review Letter
Direct characterization of photo-induced lattice dynamics in BaFe₂As₂
Ultrafast light pulses can modify electronic properties of quantum materials by perturbing the underlying, intertwined degrees of freedom. In particular, iron-based superconductors exhibit a strong coupling among electronic nematic fluctuations, spins and the lattice, serving as a playground for ultrafast manipulation. Here we use time-resolved X-ray scattering to measure the lattice dynamics of photoexcited BaFeAs. On optical excitation, no signature of an ultrafast change of the crystal symmetry is observed, but the lattice oscillates rapidly in time due to the coherent excitation of an A mode that modulates the Fe–As–Fe bond angle. We directly quantify the coherent lattice dynamics and show that even a small photoinduced lattice distortion can induce notable changes in the electronic and magnetic properties. Our analysis implies that transient structural modification can be an effective tool for manipulating the electronic properties of multi-orbital systems, where electronic instabilities are sensitive to the orbital character of bands
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