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textTwo distinct stacking orders in ReS2 are identified without ambiguity and their influence on vibrational, optical properties and carrier dynamics are investigated. With atomic resolution scanning transmission electron microscopy (STEM), two stacking orders are determined as AA stacking with negligible displacement across layers, and AB stacking with about a one-Received: ((will be filled in by the editorial staff)) Revised: ((will be filled in by the editorial staff)) Published online: ((will be filled in by the editorial staff))

Cyanate ester resins are widely utilized in high-performance printed circuit board, radar radome, communication satellite, and other fields. However, the poor toughness after curing due to the highly cross-linked and...

We measured the effect of pressure on the compressional and shear wave velocity (VP, VS) as well as density of Fe‐bearing bridgmanite, Mg0.96(1)Fe2+0.036(5)Fe3+0.014(5)Si0.99(1)O3, using impulsive stimulated light scattering, Brillouin light scattering, and X‐ray diffraction, respectively, in diamond anvil cells up to 70 GPa at 300 K. A drastic softening of VP by ~6(±1)% is observed between 42.6 and 58 GPa, while VS increases continuously with increasing pressure. A significant reduction in Poisson's ratio from 0.24 to 0.16 occurs at ~42.6–58 GPa, while VS increases by ~3(±1)% above ~40 GPa compared to MgSiO3‐bridgmanite. Thermoelastic modeling of the experimental results shows that the observed elastic anomaly of Fe‐bearing bridgmanite is consistent with a spin transition of octahedrally coordinated Fe3+ in bridgmanite. These results challenge traditional views that Fe enrichment will reduce seismic velocities, suggesting that seismic heterogeneities in the mid‐lower mantle may be due to a spin transition of Fe in Fe‐bearing bridgmanite.

The recent observation of unusually high thermal conductivity exceeding 1000 W m−1 K−1 in single‐crystal boron arsenide (BAs) has led to interest in the potential application of this semiconductor for thermal management. Although both the electron/hole high mobilities have been calculated for BAs, there is a lack of experimental investigation of its electronic properties. Here, a photoluminescence (PL) measurement of single‐crystal BAs at different temperatures and pressures is reported. The measurements reveal an indirect bandgap and two donor–acceptor pair (DAP) recombination transitions. Based on first‐principles calculations and time‐of‐flight secondary‐ion mass spectrometry results, the two DAP transitions are confirmed to originate from Si and C impurities occupying shallow energy levels in the bandgap. High‐pressure PL spectra show that the donor level with respect to the conduction band minimum shrinks with increasing pressure, which affects the release of free carriers from defect states. These findings suggest the possibility of strain engineering of the transport properties of BAs for application in electronic devices.