We study the spin Hall effect (SHE) in disordered $\pi$-conjugated organic solids, where individual molecules are oriented randomly and electrical conduction is via carrier hopping. The SHE, which arises from interference between direct ($i\to j$) and indirect ($i\to k\to j$) hoppings in a triad consisting of three molecules $i$, $j$, and $k$, is found to be proportional to $\lambda ({\mathit{n}}_i\times {\mathit{n}}_j+{\mathit{n}}_j\times {\mathit{n}}_k+{\mathit{n}}_k\times {\mathit{n}}_i)$, where $\lambda$ is the spin admixture of $\pi$ electrons due to the spin-orbit coupling and ${\mathit{n}}_i$ is the orientation vector of molecule $i$. Electrical conductivity ${\sigma }_{qq}$ ($q=x,y,z$) and spin Hall conductivity ${\sigma }_{\text{sh}}$ are computed by numerically solving the master equations of a system containing $32\times 32\times 32$ molecules and summing over contributions from all triads in the system. The obtained value of the spin Hall angle ${\mathrm{\Theta }}_{\text{sh}}$ is consistent with experimental data in PEDOT:PSS, with a predicted temperature dependence of $\log {\mathrm{\Theta }}_{\text{sh}}\sim T^{-1/4}$.

We derive an analytic solution for the ensemble-averaged collective dephasing dynamics of $N$ noninteracting atoms in a fluctuating homogeneous external field. The obtained Kraus map is used to specify families of states whose entanglement properties are preserved at all times under arbitrary field orientations, even for states undergoing incoherent evolution. Our results apply to arbitrary spectral distributions of the field fluctuations.

Quantum thermodynamics can be understood as a resource theory, whereby thermal states are free and the only allowed operations are unitary transformations commuting with the total Hamiltonian of the system. Previous literature on the subject has just focused on transformations between different state resources, overlooking the fact that quantum operations which do not commute with the total energy also constitute a potentially valuable resource. In this Letter, given a number of nonthermal quantum channels, we study the problem of how to integrate them in a thermal engine so as to distill a maximum amount of work. We find that, in the limit of asymptotically many uses of each channel, the distillable work is an additive function of the considered channels, computable for both finite dimensional quantum operations and bosonic channels. We apply our results to bound the amount of distillable work due to the natural nonthermal processes postulated in the Ghirardi-Rimini-Weber (GRW) collapse model. We find that, although GRW theory predicts the possibility of extracting work from the vacuum at no cost, the power which a collapse engine could, in principle, generate is extremely low.

Once a light axionlike scalar field couples to the electroweak gauge bosons, its classical motion during reheating induces an effective chemical potential for the fermion number. In the presence of rapid lepton number ($L$)-violating processes in the plasma, such a chemical potential provides a favorable opportunity for baryogenesis via leptogenesis. We are able to demonstrate that $L$ violation due to the exchange of heavy Majorana neutrinos is sufficient for a successful realization of this idea. Our mechanism represents a novel and minimal alternative to thermal leptogenesis, which turns out to be insensitive to the masses and $CP$-violating phases in the heavy neutrino sector. It is consistent with heavy neutrino masses close to the scale of grand unification and, quite complementary to thermal leptogenesis, requires the reheating temperature to be at least of order ${10}^{12}\mathrm{GeV}$.

We have studied the associative ionization of a Rydberg atom and a ground-state atom in an ultracold Rydberg gas. The measured scattering cross section is 3 orders of magnitude larger than the geometrical size of the produced molecule. This giant enhancement of the reaction kinetics is due to an efficient directed mass transport which is accelerated by the Rydberg electron. We also find that the total inelastic scattering cross section is given by the geometrical size of the Rydberg electron’s wave function.

We report an improved test of the weak equivalence principle by using a simultaneous ${}^{85}\mathrm{Rb}\text{−}{}^{87}\mathrm{Rb}$ dual-species atom interferometer. We propose and implement a four-wave double-diffraction Raman transition scheme for the interferometer, and demonstrate its ability in suppressing common-mode phase noise of Raman lasers after their frequencies and intensity ratios are optimized. The statistical uncertainty of the experimental data for Eötvös parameter $\eta$ is $0.8\times 10^{-8}$ at 3200 s. With various systematic errors corrected, the final value is $\eta =(2.8\pm 3.0)\times 10^{-8}$. The major uncertainty is attributed to the Coriolis effect.

We report the measurement of the inhomogeneous linewidth, homogeneous linewidth, and spin-state lifetime of ${\mathrm{Pr}}^{3+}$ ions in a novel waveguide architecture. The ${\mathrm{TeO}}_2$ slab waveguide deposited on a bulk ${\mathrm{Pr}}^{3+}:{\mathrm{Y}}_2{\mathrm{SiO}}_5$ crystal allows the ${{}^3\mathrm{H}}_4{\leftrightarrow }^1{\mathrm{D}}_2$ transition of ${\mathrm{Pr}}^{3+}$ ions to be probed by the optical evanescent field that extends into the substrate. The 2-GHz inhomogeneous linewidth, the optical coherence time of $70\pm 5\mu \mathrm{s}$, and the spin-state lifetime of $9.8\pm 0.3\mathrm{s}$ indicate that the properties of ions interacting with the waveguide mode are consistent with those of bulk ions. This result establishes the foundation for large, integrated, and high performance rare-earth-ion quantum systems based on a waveguide platform.

Bilayer graphene (BLG) with a tunable band gap appears interesting as an alternative to graphene for practical applications; thus, its transport properties are being actively pursued. Using density functional theory and perturbation analysis, we investigated, under an external electric field, the electronic properties of BLG in various stackings relevant to recently observed complex structures. We established the first phase diagram summarizing the stacking-dependent gap openings of BLG for a given field. We further identified high-density midgap states, localized on grain boundaries, even under a strong field, which can considerably reduce the overall transport gap.

A bent lithium niobate strip was exposed to a $400\text{−}\mathrm{GeV}/c$ proton beam at the external lines of CERN Super Proton Synchrotron to probe its capabilities versus coherent interactions of the particles with the crystal such as channeling and volume reflection. Lithium niobate (${\mathrm{LiNbO}}_3$) exhibits an interplanar electric field comparable to that of Silicon (Si) and remarkable piezoelectric properties, which could be exploited for the realization of piezo-actuated devices for the control of high-energy particle beams. In contrast to Si and germanium (Ge), ${\mathrm{LiNbO}}_3$ shows an intriguing effect; in spite of a low channeling efficiency (3%), the volume reflection maintains a high deflection efficiency (83%). Such discrepancy was ascribed to the high concentration ($10^4\mathrm{per}{\mathrm{cm}}^2$) of dislocations in our sample, which was obtained from a commercial wafer. Indeed, it has been theoretically shown that a channeling efficiency comparable with that of Si or Ge would be attained with a crystal at low defect concentration (less than ten per ${\mathrm{cm}}^2$). To better understand the role of dislocations on volume reflection, we have worked out computer simulation via dynecharm++ Monte Carlo code to study the effect of dislocations on volume reflection. The results of the simulations agree with experimental records, demonstrating that volume reflection is more robust than channeling in the presence of dislocations.

We present a heterogeneous version of Maxwell’s theory of viscoelasticity based on the assumption of spatially fluctuating local viscoelastic coefficients. The model is solved in coherent-potential approximation. The theory predicts an Arrhenius-type temperature dependence of the viscosity in the vanishing-frequency limit, independent of the distribution of the activation energies. It is shown that this activation energy is generally different from that of a diffusing particle with the same barrier-height distribution, which explains the violation of the Stokes-Einstein relation observed frequently in glasses. At finite but low frequencies, the theory describes low-temperature asymmetric alpha relaxation. As examples, we report the good agreement obtained for selected inorganic, metallic, and organic glasses. At high frequencies, the theory reduces to heterogeneous elasticity theory, which explains the occurrence of the boson peak and related vibrational anomalies.

Extraordinarily high mobility of Si and Ge atoms at semiconductor (Si, Ge)-metal (Al) interfaces is observed at temperatures as low as 80 K during thin metal film deposition. In situ x-ray photoemission spectroscopic valence-band measurements reveal a changed chemical bonding nature of the semiconductor atoms, from localized covalentlike to delocalized metalliclike, at the interface with the Al metal. The resulting delocalized bonding nature of the interfacial semiconductor atoms brings about the observed extreme enhancement of their mobility. The finding opens avenues for tailoring reaction kinetics and phase transformations in nanostructured materials, as functional thin-film systems, at ultralow temperatures by dedicated interfacial design.

Employing smart Monte Carlo sampling techniques within the grand canonical ensemble, we investigate the properties of water at a model hydrophobic substrate. By reducing the strength of substrate-water attraction, we find that fluctuations in the local number density, quantified by a rigorous definition of the local compressibility $\chi (z)$, increase rapidly for distances $z$ within one or two molecular diameters from the substrate as the degree of hydrophobicity, measured by the macroscopic contact angle $\theta$, increases. Our simulations provide evidence for a continuous (critical) drying transition as the substrate-water interaction becomes very weak: $\cos (\theta )\to -1$. We speculate that the existence of such a transition might account for earlier simulation observations of strongly enhanced density fluctuations.