Nematicity dynamics in the charge-density-wave phase of a cuprate superconductor

Understanding the interplay between charge, nematic, and structural ordering tendencies in cuprate superconductors is critical to unraveling their complex phase diagram. Using pump-probe time-resolved resonant x-ray scattering on the (0 0 1) Bragg peak at the Cu L3 and oxygen K resonances, we investigate non-equilibrium dynamics of Qa = Qb = 0 nematic order and its association with both charge density wave (CDW) order and lattice dynamics in La1.65Eu0.2Sr0.15CuO4. In contrast to the slow lattice dynamics probed at the apical oxygen K resonance, fast nematicity dynamics are observed at the Cu L3 and planar oxygen K resonances. The temperature dependence of the nematicity dynamics is correlated with the onset of CDW order. These findings unambiguously indicate that the CDW phase, typically evidenced by translational symmetry breaking, includes a significant electronic nematic component.Comment: 16 pages, 4 figure

A Demand-Driven Perspective on Generative Audio AI

To achieve successful deployment of AI research, it is crucial to understand the demands of the industry. In this paper, we present the results of a survey conducted with professional audio engineers, in order to determine research priorities and define various research tasks. We also summarize the current challenges in audio quality and controllability based on the survey. Our analysis emphasizes that the availability of datasets is currently the main bottleneck for achieving high-quality audio generation. Finally, we suggest potential solutions for some revealed issues with empirical evidence.Comment: 10 pages, 7 figure

Fully Stretchable Optoelectronic Sensors Based on Colloidal Quantum Dots for Sensing Photoplethysmographic Signals

Flexible and stretchable optoelectronic devices can be potentially applied in displays, biosensors, biomedicine, robotics, and energy generation. The use of nanomaterials with superior optical properties such as quantum dots (QDs) is important in the realization of wearable displays and biomedical devices, but specific structural design as well as selection of materials should preferentially accompany this technology to realize stretchable forms of these devices. Here, we report stretchable optoelectronic sensors manufactured using colloidal QDs and integrated with elastomeric substrates, whose optoelectronic properties are stable under various deformations. A graphene electrode is adopted to ensure extreme bendability of the devices. Ultrathin QD light emitting diodes and QD photodetectors are transfer-printed onto a prestrained elastomeric layout to form wavy configurations with regular patterns. The layout is mechanically stretchable until the structure is converted to a flat configuration. The emissive and active area itself can be stretched or compressed by buckled structures, which are applicable to wearable electronic devices. We demonstrate that these stretchable optoelectronic sensors can be used for continuous monitoring of blood waves via photoplethysmography signal recording. These and related systems create important and unconventional opportunities for stretchable and foldable optoelectronic devices with health-monitoring capability and, thus, meet the demand for wearable and body-integrated electronics

4D Visualization of a Nonthermal Coherent Magnon in a Laser Heated Lattice by an X-ray Free Electron Laser

Ultrafast optical manipulation of magnetic phenomena is an exciting achievement of mankind, expanding one's horizon of knowledge toward the functional nonequilibrium states. The dynamics acting on an extremely short timescale push the detection limits that reveal fascinating light-matter interactions for nonthermal creation of effective magnetic fields. While some cases are benchmarked by emergent transient behaviors, otherwise identifying the nonthermal effects remains challenging. Here, a femtosecond time-resolved resonant magnetic X-ray diffraction experiment is introduced, which uses an X-ray free-electron laser (XFEL) to distinguish between the effective field and the photoinduced thermal effect. It is observed that a multiferroic Y-type hexaferrite exhibits magnetic Bragg peak intensity oscillations manifesting entangled antiferromagnetic (AFM) and ferromagnetic (FM) Fourier components of a coherent AFM magnon. The magnon trajectory constructed in 3D space and time domains is decisive to evince ultrafast field formation preceding the lattice thermalization. A remarkable impact of photoexcitation across the electronic bandgap is directly unraveled, amplifying the photomagnetic coupling that is one of the highest among AFM dielectrics. Leveraging the above-bandgap photoexcitation, this energy-efficient optical process further suggests a novel photomagnetic control of ferroelectricity in multiferroics

Author Correction: Ultrafast X-ray imaging of the light-induced phase transition in VO2 (Nature Physics, (2022), 10.1038/s41567-022-01848-w)

In the version of this article initially published, the Acknowledgements was missing thanks from Soonnam Kwon for support from the National Research Foundation of Korea (NRF-2020R1A2C1007416). The error has been corrected in the HTML and PDF versions of the article

Optical control of ultrafast structural dynamics in a fluorescent protein.

The photoisomerization reaction of a fluorescent protein chromophore occurs on the ultrafast timescale. The structural dynamics that result from femtosecond optical excitation have contributions from vibrational and electronic processes and from reaction dynamics that involve the crossing through a conical intersection. The creation and progression of the ultrafast structural dynamics strongly depends on optical and molecular parameters. When using X-ray crystallography as a probe of ultrafast dynamics, the origin of the observed nuclear motions is not known. Now, high-resolution pump-probe X-ray crystallography reveals complex sub-ångström, ultrafast motions and hydrogen-bonding rearrangements in the active site of a fluorescent protein. However, we demonstrate that the measured motions are not part of the photoisomerization reaction but instead arise from impulsively driven coherent vibrational processes in the electronic ground state. A coherent-control experiment using a two-colour and two-pulse optical excitation strongly amplifies the X-ray crystallographic difference density, while it fully depletes the photoisomerization process. A coherent control mechanism was tested and confirmed the wave packets assignment

Optical control of ultrafast structural dynamics in a fluorescent protein

The photoisomerization reaction of a fluorescent protein chromophore occurs on the ultrafast timescale. The structural dynamics that result from femtosecond optical excitation have contributions from vibrational and electronic processes and from reaction dynamics that involve the crossing through a conical intersection. The creation and progression of the ultrafast structural dynamics strongly depends on optical and molecular parameters. When using X-ray crystallography as a probe of ultrafast dynamics, the origin of the observed nuclear motions is not known. Now, high-resolution pump–probe X-ray crystallography reveals complex sub-ångström, ultrafast motions and hydrogen-bonding rearrangements in the active site of a fluorescent protein. However, we demonstrate that the measured motions are not part of the photoisomerization reaction but instead arise from impulsively driven coherent vibrational processes in the electronic ground state. A coherent-control experiment using a two-colour and two-pulse optical excitation strongly amplifies the X-ray crystallographic difference density, while it fully depletes the photoisomerization process. A coherent control mechanism was tested and confirmed the wave packets assignment.peerReviewe