The transverse momentum ($p_T$) distribution of primary charged particles is measured in minimum bias (non-single-diffractive) $p+\mathrm{Pb}$ collisions at $\sqrt{s_{NN}}=5.02\mathrm{TeV}$ with the ALICE detector at the LHC. The $p_T$ spectra measured near central rapidity in the range $0.5<p_T<20\mathrm{GeV}/c$ exhibit a weak pseudorapidity dependence. The nuclear modification factor $R_{p\mathrm{Pb}}$ is consistent with unity for $p_T$ above $2\mathrm{GeV}/c$. This measurement indicates that the strong suppression of hadron production at high $p_T$ observed in $\mathrm{Pb}+\mathrm{Pb}$ collisions at the LHC is not due to an initial-state effect. The measurement is compared to theoretical calculations.

We show that the normally weak optical quadrupole interaction in atoms is enhanced significantly when the atom interacts at near resonance with an optical vortex. In particular, the forces and torque acting on the atom are shown here to scale up with the square of the winding number $l$ of the vortex. Because the integer $l$ can be arranged to be large, this property allows for processes involving dipole-forbidden, but quadrupole-allowed, transitions in atoms, such as cesium and oxygen, to come into play. We show that the mechanical effects of vortex light on atoms involving translational and rotational motion as well as trapping should be significantly enhanced for quadrupole transitions and present novel features with useful implications for the emerging field of atomtronics.

Nuclear quantum effects are responsible for vivid large-amplitude motion in protonated methane ${\mathrm{CH}}_5^{+}$, which enables so-called “hydrogen scrambling” that leads to the dynamical equivalence of all five protons even at low temperatures. But what is the impact of external perturbations on hydrogen scrambling of ${\mathrm{CH}}_5^{+}$ in this quantum fluxional ground state? We report ab initio path integral simulations of ${\mathrm{CH}}_5^{+}({\mathrm{H}}_2{)}_n$, $n=1$, 2, 3 that demonstrate cessation of hydrogen scrambling at low temperatures (20 K), but only slowdown at moderate temperatures (110 K). Importantly, different and unexpected mechanisms that are responsible for freezing the scrambling dynamics are revealed and traced back to distinct microsolvation patterns.

A scheme for entangling distant atoms is realized, as proposed in the seminal paper by [C. Cabrillo et al., Phys. Rev. A 59, 1025 (1999)]. The protocol is based on quantum interference and detection of a single photon scattered from two effectively one meter distant laser cooled and trapped atomic ions. The detection of a single photon heralds entanglement of two internal states of the trapped ions with high rate and with a fidelity limited mostly by atomic motion. Control of the entangled state phase is demonstrated by changing the path length of the single-photon interferometer.

We show that a vapor of multilevel atoms driven by far-off-resonant laser beams, with the possibility of interference of two Raman resonances, is highly efficient for creating parity-time symmetric profiles of the probe-field refractive index, whose real part is symmetric and imaginary part is antisymmetric in space. The spatial modulation of the probe-field susceptibility is achieved by a proper combination of standing-wave strong control fields and of Stark shifts induced by far-off-resonance laser fields. As particular examples we explore a mixture of isotopes of rubidium atoms and design a parity-time symmetric lattice and a parabolic refractive index with a linear imaginary part.

High order harmonic generation from clusters is a controversial topic: conflicting theories exist, with different explanations for similar experimental observations. From an experimental point of view, separating the contributions from monomers and clusters is challenging. By performing a spectrally and spatially resolved study in a controlled mixture of clusters and monomers, we are able to isolate a region of the spectrum where the emission purely originates from clusters. Surprisingly, the emission from clusters is depolarized, which is the signature of statistical inhomogeneous emission from a low-density source. The harmonic response to laser ellipticity shows that this generation is produced by a new recollisional mechanism, which opens the way to future theoretical studies.

We derive expressions for the probability distribution of the ratio of two consecutive level spacings for the classical ensembles of random matrices. This ratio distribution was recently introduced to study spectral properties of many-body problems, as, contrary to the standard level spacing distributions, it does not depend on the local density of states. Our Wigner-like surmises are shown to be very accurate when compared to numerics and exact calculations in the large matrix size limit. Quantitative improvements are found through a polynomial expansion. Examples from a quantum many-body lattice model and from zeros of the Riemann zeta function are presented.

We investigate chaos synchronization of small-scale motions in the three-dimensional turbulent energy cascade, via pseudospectral simulations of the incompressible Navier-Stokes equations. The modes of the turbulent velocity field below about 20 Kolmogorov dissipation lengths are found to be slaved to the chaotic dynamics of larger-scale modes. The dynamics of all dissipation-range modes can be recovered to full numerical precision by solving small-scale dynamical equations with the given large-scale solution as an input, regardless of initial condition. The synchronization rate exponent scales with the Kolmogorov dissipation time scale, with possible weak corrections due to intermittency. Our results suggest that all sub-Kolmogorov length modes should be fully recoverable from numerical simulations with standard, Kolmogorov-length grid resolutions.

High Reynolds number magnetohydrodynamic turbulence in the presence of zero-flux large-scale magnetic fields is investigated as a function of the magnetic field strength. For a variety of flow configurations, the energy dissipation rate $ϵ$ follows the scaling $ϵ\propto U_{\mathrm{rms}}^3/\ell$ even when the large-scale magnetic field energy is twenty times larger than the kinetic energy. A further increase of the magnetic energy showed a transition to the $ϵ\propto U_{\mathrm{rms}}^2{B}_{\mathrm{rms}}/\ell$ scaling implying that magnetic shear becomes more efficient at this point at cascading the energy than the velocity fluctuations. Strongly helical configurations form nonturbulent helicity condensates that deviate from these scalings. Weak turbulence scaling was absent from the investigation. Finally, the magnetic energy spectra support the Kolmogorov spectrum $k^{-5/3}$ while kinetic energy spectra are closer to the Iroshnikov-Kraichnan spectrum $k^{-3/2}$ as observed in the solar wind.

Cold-atom systems offer a great potential for the future design of new mesoscopic quantum systems with properties that are fundamentally different from semiconductor nanostructures. Here, we investigate the quantum-gas analogue of a quantum wire and find a new scenario for the quantum transport: Attractive interactions may lead to a complete suppression of current in the low-bias range, a total current blockade. We demonstrate this effect for the example of ultracold quantum gases with dipolar interactions.

We report measurements of the acoustic and optical phason dispersion curves associated with the lattice of partial dislocations on the reconstructed (111) surface of gold. Our measurements of these low energy ($<0.5\mathrm{meV}$) weakly dispersive modes have been enabled by the very high resolution of the novel helium spin-echo technique. The results presented here constitute the first measurement of the phason dispersion of misfit dislocations, and possibly of excitations associated with any type of crystalline dislocations.

By carefully tuning the thickness of a compliant thin film placed within an acoustic cavity, we achieve coherent control of the cavity’s acoustic resonances, analogous to the operation of an optical etalon. This technique is demonstrated using a supported membrane oscillator in which multiple high-frequency harmonic resonances are simultaneously optoexcited by an ultrafast laser. Theoretical and computational methods are used to analyze the selective strengthening or suppression of these resonances by constructive or destructive interference.

Intercalation of Eu under graphene on Ir(111) results in patterns oriented along the graphene moiré and quantized in size by its unit mesh. The patterns are formed by stripes, compact islands, and channels. Over a wide range of intercalated amounts the step concentration of the pattern has a rather constant saturation value. These findings are explained by the chemically modulated binding of graphene to the substrate and the preexisting strain in graphene due to its cooldown from the growth temperature. Local variations in the intercalation step density appear to reflect local variations in the preexisting strain.

We study finite-time Landau-Zener transitions at a singlet-triplet level crossing in a GaAs double quantum dot, both experimentally and theoretically. Sweeps across the anticrossing in the high driving speed limit result in oscillations with a small visibility. Here we demonstrate how to increase the oscillation visibility while keeping sweep times shorter than $T_2^{*}$ using a tailored pulse with a detuning dependent level velocity. Our results show an improvement of a factor of $\sim 2.9$ for the oscillation visibility. In particular, we were able to obtain a visibility of $\sim 0.5$ for Stückelberg oscillations, which demonstrates the creation of an equally weighted superposition of the qubit states.

We have directly imaged the anisotropic nonlinear Meissner effect in an unconventional superconductor through the nonlinear electrodynamic response of both (bulk) gap nodes and (surface) Andreev bound states. A superconducting thin film is patterned into a compact self-resonant spiral structure, excited near resonance in the radio-frequency range, and scanned with a focused laser beam perturbation. At low temperatures, direction-dependent nonlinearities in the reactive and resistive properties of the resonator create photoresponse that maps out the directions of nodes, or of bound states associated with these nodes, on the Fermi surface of the superconductor. The method is demonstrated on the nodal superconductor ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta }$ and the results are consistent with theoretical predictions for the bulk and surface contributions.

In multiband superconductors, each superconducting condensate supports vortices with fractional quantum flux. In the ground state, vortices in different bands are spatially bounded together to form a composite vortex, carrying one quantum flux ${\Phi }_0$. Here we predict dissociation of the composite vortices lattice in the flux flow state due to the disparity of the vortex viscosity and flux of the vortex in different bands. For a small driving current, composite vortices start to deform, but the constituting vortices in different bands move with the same velocity. For a large current, composite vortices dissociate and vortices in different bands move with different velocities. The dissociation transition shows up as an increase of flux flow resistivity. In the dissociated phase, Shapiro steps are developed when an ac current is superimposed with a dc current.

The modern expressions for polarization $\mathbf{P}$ and orbital magnetization $\mathbf{M}$ are $\mathbf{k}$-space integrals. But a genuine bulk property should also be expressible in $\mathbf{r}$ space, as an unambiguous function of the ground-state density matrix, “nearsighted” in insulators, independently of the boundary conditions—either periodic or open. While $\mathbf{P}$—owing to its “quantum” indeterminacy—is not a bulk property in this sense, $\mathbf{M}$ is. We provide its $\mathbf{r}$-space expression for any insulator, even with a nonzero Chern invariant. Simulations on a model Hamiltonian validate our theory.

In sharp contrast to previous studies on FeRh bulk, thin films, and nanoparticles, we report the persistence of ferromagnetic order down to 3 K for size-selected 3.3 nm diameter nanocrystals embedded into an amorphous carbon matrix. The annealed nanoparticles have a $B2$ structure with alternating atomic Fe and Rh layers. X-ray magnetic dichroism and superconducting quantum interference device measurements demonstrate ferromagnetic alignment of the Fe and Rh magnetic moments of 3 and $1{\mu }_{\mathrm{B}}$, respectively. The ferromagnetic order is ascribed to the finite-size induced structural relaxation observed in extended x-ray absorption spectroscopy.

We investigated by optical microscopy the thermal transition of the spin-crossover dinuclear iron(II) compound [$\{\mathrm{Fe}(\mathrm{NCSe})(\mathrm{py}{)}_2{\}}_2(m\mathrm{\text{−}}\mathrm{bpypz})$]. In a high-quality crystal the high-spin (HS) low-spin (LS) thermal transition took place with a sizable hysteresis, at $\sim 108\mathrm{K}$ and $\sim 116\mathrm{K}$ on cooling and heating, respectively, through the growth of a single macroscopic domain with a straight LS and HS interface. The interface orientation was almost constant and its propagation velocity was close to $\sim 6$ and $26\mu \mathrm{m}{\mathrm{s}}^{-1}$ for the on-cooling and on-heating processes, respectively. We found that the motion of the interface was sensitive to the intensity of the irradiation beam of the microscope, through a photothermal effect. By fine-tuning the intensity we could stop and even reverse the interface motion. This way we stabilized a biphasic state of the crystal, and we followed the spontaneous motion of the interface at different temperatures inside the thermal hysteresis loop. This experiment gives access for the first time to an accurate determination of the equilibrium temperature in the case of thermal hysteresis—which was not accessible by the usual quasistatic investigations. The temperature dependence of the propagation velocity inside the hysteretic interval was revealed to be highly nonlinear, and it was quantitatively reproduced by a dynamical mean-field theory, which made possible an estimate of the macroscopic energy barrier.

We demonstrate that yellow luminescence often observed in both carbon-doped and pristine GaN is the result of electronic transitions via the ${\mathrm{C}}_{\mathrm{N}}\mathrm{\text{−}}{\mathrm{O}}_{\mathrm{N}}$ complex. In contrast to common isolated defects, the ${\mathrm{C}}_{\mathrm{N}}\mathrm{\text{−}}{\mathrm{O}}_{\mathrm{N}}$ complex is energetically favorable, and its calculated optical properties, such as absorption and emission energies, a zero phonon line, and the thermodynamic transition level, all show excellent agreement with measured luminescence data. Thus, by combining hybrid density functional theory and experimental measurements, we propose a solution to a long-standing problem of the GaN yellow luminescence.