Ultraquantum magnetoresistance in Kramers Weyl semimetal candidate β\beta-Ag2Se

The topological semimetal $\beta$-Ag2Se features a Kramers Weyl node at the origin in momentum space and a quadruplet of spinless Weyl nodes, which are annihilated by spin-orbit coupling. We show that single crystalline $\beta$-Ag2Se manifests giant Shubnikov-de Haas oscillations in the longitudinal magnetoresistance which stem from a small electron pocket that can be driven beyond the quantum limit by a field less than 9 T. This small electron pocket is a remainder of the spin-orbit annihilatedWeyl nodes and thus encloses a Berry-phase structure. Moreover, we observed a negative longitudinal magnetoresistance when the magnetic field is beyond the quantum limit. Our experimental findings are complemented by thorough theoretical band structure analyses of this Kramers Weyl semimetal candidate, including first-principle calculations and an effective k*p model.Comment: A new version based on arXiv:1502.0232

Ghost Dog

The single crystal of the extra-large pore zeolite, ITQ-33, was obtained and used to explore its crystal structure details. The ITQ-33 structure was found to be disordered with the columnar periodic building unit, explaining the morphology changes upon the different Si/Ge ratio, and the formation of the hierarchical structure from assembling of ITQ-33 nanofibers

Self-Imaging of Molecules from Diffraction Spectra by Laser-Induced Rescattering Electrons

We study high-energy angle-resolved photoelectron spectra of molecules in strong fields. In an oscillating laser electric field, electrons released earlier in the pulse may return to recollide with the target ion, in a process similar to scattering by laboratory prepared electrons. If midinfrared lasers are used, we show that the images generated by the returning electrons are similar to images observed in typical gas-phase electron diffraction (GED). These spectra can be used to retrieve the positions of atoms in a molecule as in GED. Since infrared laser pulses of durations of a few femtoseconds are already available today, the study of these high-energy photoelectrons offers the opportunity of imaging the structure of transient molecules with temporal resolution of a few femtoseconds

Signature of Ericson Fluctuations in Helium Inelastic Scattering Cross Sections Near the Double Ionization Threshold

We calculated the inelastic electron impact excitation cross sections of He⁺ by electrons for a model helium atom to examine the onset of the signature of quantum chaotic scattering in this simple system. We find Ericson fluctuations (EF) in the calculated inelastic scattering cross sections only when the impact energies lie within about 0.21 eV below the double ionization threshold. We also discuss the stringent requirements and the proper methods for analyzing the inelastic scattering cross sections in order to observe EF experimentally

Single crystal of a one-dimensional metallo-covalent organic framework.

Although polymers have been studied for well over a century, there are few examples of covalently linked polymer crystals synthesised directly from solution. One-dimensional (1D) covalent polymers that are packed into a framework structure can be viewed as a 1D covalent organic framework (COF), but making a single crystal of this has been elusive. Herein, by combining labile metal coordination and dynamic covalent chemistry, we discover a strategy to synthesise single-crystal metallo-COFs under solvothermal conditions. The single-crystal structure is rigorously solved using single-crystal electron diffraction technique. The non-centrosymmetric metallo-COF allows second harmonic generation. Due to the presence of syntactic pendant amine groups along the polymer chains, the metallopolymer crystal can be further cross-linked into a crystalline woven network

Permanent magnetic droplet-derived microrobots

Microrobots hold substantial potential for precision medicine. However, challenges remain in balancing multifunctional cargo loading with efficient locomotion and in predicting behavior in complex biological environments. Here, we present permanent magnetic droplet-derived microrobots (PMDMs) with superior cargo loading capacity and dynamic locomotion capabilities. Produced rapidly via cascade tubing microfluidics, PMDMs can self-assemble, disassemble, and reassemble into chains that autonomously switch among four locomotion modes-walking, crawling, swinging, and lateral movement. Their reconfigurable design allows navigation through complex and constrained biomimetic environments, including obstacle negotiation and stair climbing with record speed at the submillimeter scale. We also developed a molecular dynamics-based computational platform that predicts PMDM assembly and motion. PMDMs demonstrated precise, programmable cargo delivery (e.g., drugs and cells) with postdelivery retrieval. These results establish a physical and in silico foundation for future microrobot design and represent a key step toward clinical translation