Krypton-assisted growth of low-loss α-phase tantalum on silicon stays within back-end-of-line semiconductor thermal budgets while delivering state-of-the-art qubit coherence.
Understanding and controlling valley-specific light–matter interactions and non-equilibrium microscopic coupling mechanisms lie at the heart of valleytronics. Due to their strong in-plane anisotropy, which enables polarization-controlled optical transitions to distinct non-degenerate valleys, group-IV monochalcogenides have been recently proposed as promising candidates for next-generation valleytronic materials. However, ultrafast non-equilibrium dynamics following the optical preparation of valley-polarized states have received limited attention in these systems. Here, combining time- and angle-resolved extreme-ultraviolet photoemission spectroscopy with time-dependent Boltzmann equation simulations, we investigate ultrafast valley polarization dynamics following polarization-controlled photoexcitation in SnSe. We show that selective excitation to valleys at global conduction minima yields nearly unity and time-independent valley polarization. By contrast, photoexcitation to the other valley channel leads to ultrafast decay and reversal of valley polarization on subpicosecond timescales due to intervalley scattering mediated by strong electron–phonon coupling with an optical phonon mode. Our findings reveal strongly anisotropic and radically different non-equilibrium valley physics than in most common two-dimensional valleytronics materials. Polarization-selective excitation in SnSe reveals anisotropic valley dynamics with distinct channels: one channel with near-unity valley polarization and one channel that rapidly depolarizes through electron–phonon-mediated intervalley scattering.
A p-type dopant whose radical anion decomposes after electron transfer can continuously maintain the doping reaction and boost hole densities by orders of magnitude.
Colloidal particles steered by light weave the defect lines of a nematic liquid crystal into programmable crossings, realizing non-Abelian braiding operations that can be watched, reordered and compiled in real space.
The glass transition temperatures of melting mixtures of metal–organic frameworks (MOFs) and phenanthroline are lowered through transient coordination, enabling melt-quenched vitrification of previously unmeltable MOFs.
