Although tightly focused intense ultrashort laser pulses are used in many applications from nano-processing to warm dense matter physics, their nonparaxial propagation implies the use of numerical simulations with vectorial wave equations or exact Maxwell solvers that have serious limitations and thus have hindered progress in this important field up to now. Here we present an elegant and robust solution that allows one to map the problem on one that can be addressed by simple scalar wave equations. The solution is based on a transformation optics approach and its validity is demonstrated in both the linear and the nonlinear regime. Our solution allows accessing challenging problems of extreme spatiotemporal localization of high power laser radiation that remain almost unexplored theoretically until now.

Brittle metallic glasses exhibit a unique and intriguing fracture morphology of periodic nanocorrugations whose spacing and amplitude are of the order of tens of nanometers. We show through continuum simulations that they fail by spontaneous and simultaneous cavitation within multiple weak zones arising due to intrinsic atomic density fluctuations ahead of a notch tip. Dynamic crack growth would then occur along curved but narrowly confined shear bands that link the growing cavities. This mechanism involves little dissipation and also explains the formation of nanocorrugations.

The impact of impurity ions on a pedestal has been investigated in the HL-2A Tokamak, at the Southwestern Institute of Physics, Chengdu, China. Experimental results have clearly shown that during the $H$-mode phase, an electromagnetic turbulence was excited in the edge plasma region, where the impurity ions exhibited a peaked profile. It has been found that double impurity critical gradients are responsible for triggering the turbulence. Strong stiffness of the impurity profile has been observed during cyclic transitions between the $I$-phase and $H$-mode regime. The results suggest that the underlying physics of the self-regulated edge impurity profile offers the possibility for an active control of the pedestal dynamics via pedestal turbulence.

The ground state and transport properties of the Lieb lattice flat band in the presence of an attractive Hubbard interaction are considered. It is shown that the superfluid weight can be large even for an isolated and strictly flat band. Moreover the superfluid weight is proportional to the interaction strength and to the quantum metric, a band structure quantity derived solely from the flat-band Bloch functions. These predictions are amenable to verification with ultracold gases and may explain the anomalous behavior of the superfluid weight of high-$T_c$ superconductors.

At the jamming transition, amorphous packings are known to display anomalous vibrational modes with a density of states (DOS) that remains constant at low frequency. The scaling of the DOS at higher packing fractions remains, however, unclear. One might expect to find a simple Debye scaling, but recent results from effective medium theory and the exact solution of mean-field models both predict an anomalous, non-Debye scaling. Being mean-field in nature, however, these solutions are only strictly valid in the limit of infinite spatial dimension, and it is unclear what value they have for finite-dimensional systems. Here, we study packings of soft spheres in dimensions 3 through 7 and find, away from jamming, a universal non-Debye scaling of the DOS that is consistent with the mean-field predictions. We also consider how the soft mode participation ratio evolves as dimension increases.

Applications of superoleophobic surfaces depend on the stability of the air cushion formed under liquid drops. To analyze the longevity of air cushions we used reflection-interference contrast microscopy (RICM) for drops on a porous fractal-like structure of sintered nanoparticles. RICM permits us to monitor the height of the air cushion with nanometer resolution. Whereas the air cushion under all investigated liquids was stable on a time scale of a few seconds to minutes and liquids rolled off, liquids with low surface tension penetrated the coating on the time scale of hours and longer. The penetration speed showed a power law dependence on time, $dz/dt\sim t^p$, the exponent $p$ varying from $-0.5$ to $-1.2$. Thus, penetration is qualitatively different from the Lucas-Washburn law that governs spontaneous capillary filling of porous structures.

We present thermoelectric power and resistivity measurements in the ferromagnetic superconductor URhGe for a magnetic field applied along the hard magnetization $b$ axis of the orthorhombic crystal. Reentrant superconductivity is observed near the spin reorientation transition at $H_R=12.75\mathrm{T}$, where a first order transition from the ferromagnetic to the polarized paramagnetic state occurs. Special focus is given to the longitudinal configuration, where both the electric and heat current are parallel to the applied field. The validity of the Fermi-liquid $T^2$ dependence of the resistivity through $H_R$ demonstrates clearly that no quantum critical point occurs at $H_R$. Thus, the ferromagnetic transition line at $H_R$ becomes first order implying the existence of a tricritical point at finite temperature. The enhancement of magnetic fluctuations in the vicinity of the tricritical point stimulates the reentrance of superconductivity. The abrupt sign change observed in the thermoelectric power with the thermal gradient applied along the $b$ axis together with the strong anomalies in the other directions is definitive macroscopic evidence that in addition a significant change of the Fermi surface appears through $H_R$.

Using tunneling spectroscopy, we show that pseudogaps emerge in strongly correlated, two-dimensional electron liquids in ${\mathrm{SrTiO}}_3$ quantum wells that are tuned near a quantum critical point. Coherence peaks emerge at low temperatures in quantum wells embedded in antiferromagnetic ${\mathrm{SmTiO}}_3$ that remain itinerant to the lowest thickness. Quantum wells embedded in ferrimagnetic ${\mathrm{GdTiO}}_3$ that become ferromagnetic at low temperatures show no indication of quasiparticle coherence. They undergo a symmetry-lowering metal-to-insulator transition at the lowest thicknesses that coincides with a vanishing single-particle density of states (DOS) around the Fermi level. Both types of quantum wells show a power-law depletion of the DOS at high energies. The results show that the different pseudogap behaviors are closely correlated with the type of magnetism in the proximity of the quantum wells and thus provide insights into the microscopic mechanisms.

We study transport properties of graphene with anisotropically distributed on-site impurities (adatoms) that are randomly placed on every third line drawn along carbon bonds. We show that stripe states characterized by strongly suppressed backscattering are formed in this model in the direction of the lines. The system reveals Lévy-flight transport in the stripe direction such that the corresponding conductivity increases as the square root of the system length. Thus, adding this type of disorder to clean graphene near the Dirac point strongly enhances the conductivity, which is in stark contrast with a fully random distribution of on-site impurities, which leads to Anderson localization. The effect is demonstrated both by numerical simulations using the Kwant code and by an analytical theory based on the self-consistent $T$-matrix approximation.

The correlation between magnetic and dielectric properties has been investigated for the single crystal of the chiral triangular-lattice helimagnet ${\mathrm{MnSb}}_2{\mathrm{O}}_6$. We found that the spin-spiral plane in the ground state has a considerable tilting from the (110) plane and that the sign of the spin-spiral tilting angle is coupled to the clockwise or counterclockwise manner of spin rotation and accordingly to the sign of magnetically induced electric polarization. This leads to unique magnetoelectric responses such as the magnetic-field-induced selection of a single ferroelectric domain as well as the reversal of electric polarization just by a slight tilting of the magnetic field direction, where the chiral nature of the crystal structure plays a crucial role through the coupling of the chirality between the crystal and magnetic structures. Our results demonstrate that crystallographic chirality can be an abundant source of novel magnetoelectric functions with coupled internal degrees of freedom.

Impulsive interband excitation with femtosecond near-infrared pulses establishes a plasma response in intrinsic germanium structures fabricated on a silicon substrate. This direct approach activates the plasmonic resonance of the Ge structures and enables their use as optical antennas up to the mid-infrared spectral range. The optical switching lasts for hundreds of picoseconds until charge recombination redshifts the plasma frequency. The full behavior of the structures is modeled by the electrodynamic response established by an electron-hole plasma in a regular array of antennas.

We present a novel replica trick that computes the relative entropy of two arbitrary states in conformal field theory. Our replica trick is based on the analytic continuation of partition functions that break the $Z_n$ replica symmetry. It provides a method for computing arbitrary matrix elements of the modular Hamiltonian corresponding to excited states in terms of correlation functions. We show that the quantum Fisher information in vacuum can be expressed in terms of two-point functions on the replica geometry. We perform sample calculations in two-dimensional conformal field theories.

Using $1.09\times {10}^9$ $J/\psi$ events collected by the BESIII experiment in 2012, we study the $J/\psi \to \gamma {\eta }^{\prime }{\pi }^{+}{\pi }^{-}$ process and observe a significant abrupt change in the slope of the ${\eta }^{\prime }{\pi }^{+}{\pi }^{-}$ invariant mass distribution at the proton-antiproton ($p\overline{p}$) mass threshold. We use two models to characterize the ${\eta }^{\prime }{\pi }^{+}{\pi }^{-}$ line shape around $1.85\mathrm{GeV}/c^2$: one that explicitly incorporates the opening of a decay threshold in the mass spectrum (Flatté formula), and another that is the coherent sum of two resonant amplitudes. Both fits show almost equally good agreement with data, and suggest the existence of either a broad state around $1.85\mathrm{GeV}/c^2$ with strong couplings to the $p\overline{p}$ final states or a narrow state just below the $p\overline{p}$ mass threshold. Although we cannot distinguish between the fits, either one supports the existence of a $p\overline{p}$ moleculelike state or bound state with greater than $7\sigma$ significance.

We demonstrate a robust, all-solid-state approach for the generation of microjoule subcycle pulses in the midinfrared through a cascade of carefully optimized parametric-amplification, difference-frequency-generation, spectral-broadening, and chirp-compensation stages. This method of subcycle waveform generation becomes possible due to an unusual, ionization-assisted solid-state pulse self-compression dynamics, where highly efficient spectral broadening is enabled by ultrabroadband four-wave parametric amplification phase matched near the zero-group-velocity wavelength of the material.

In the present Letter, we theoretically demonstrate that near-field radiative transport between one-dimensional periodic grating microstructures separated by nanometer vacuum gaps can be spectrally enhanced by exciting magnetic polaritons. Fluctuational electrodynamics that incorporates scattering matrix theory with rigorous coupled-wave analysis is employed to exactly calculate the near-field radiative flux between two metallic gratings. In addition to the well-known coupled surface plasmon polaritons, the radiative flux can be also spectrally enhanced due to the magnetic polariton, which is excited in the gap between the grating ridges. The mechanism of magnetic polaritons in the near-field radiative transport are elucidated in detail, while the unusual enhancement cannot be predicted by either Derjaguin’s or the effective medium approximations. The effects of the vacuum gap distance and grating geometry parameters between the two gratings are investigated. The findings will open a new way to spectrally control near-field radiative transfer by magnetic polaritons with micro- or nanostructured metamaterials, which holds great potential for improving the performance of energy systems like near-field thermophotovoltaics.

Under nonequilibrium conditions, bosonic modes can become dynamically unstable with an exponentially growing occupation. On the other hand, topological band structures give rise to symmetry protected midgap states. In this Letter, we investigate the interplay of instability and topology. Thereby, we establish a general relation between topology and instability under ac driving. We apply our findings to create dynamical instabilities which are strongly localized at the boundaries of a finite-size system. As these localized instabilities are protected by symmetry, they can be considered as topological instabilities.

We report on the self-organized growth of monatomic transition-metal oxide chains of ($3\times 1$) periodicity and unusual $M{\mathrm{O}}_2$ stoichiometry ($M=\mathrm{Ni}$, Co, Fe, Mn) on Ir(100). We analyze their structural and magnetic properties by means of quantitative LEED, STM, and density functional theory (DFT) calculations. LEED analyses reveal a fascinating common atomic structure in which the transition-metal atoms sit above a missing-row structure of the surface and are coupled to the substrate only via oxygen atoms. This structure is confirmed by DFT calculations with structural parameters deviating by less than 1.7 pm. The DFT calculations predict that the ${\mathrm{NiO}}_2$ chains are nonmagnetic, ${\mathrm{CoO}}_2$ chains are ferromagnetic, while ${\mathrm{FeO}}_2$ and ${\mathrm{MnO}}_2$ are antiferromagnetic. All structures show only weak magnetic interchain coupling. Further, we demonstrate the growth of oxide chains of binary alloys of Co and Ni or Fe on Ir(100), which allows us to produce well-controlled ensembles of ferromagnetic chains of different lengths separated by nonmagnetic or antiferromagnetic segments.

Semiconducting half and, to a lesser extent, full Heusler compounds are promising thermoelectric materials due to their compelling electronic properties with large power factors. However, intrinsically high thermal conductivity resulting in a limited thermoelectric efficiency has so far impeded their widespread use in practical applications. Here, we report the computational discovery of a class of hitherto unknown stable semiconducting full Heusler compounds with ten valence electrons ($X_{2}YZ$, $X=\mathrm{Ca}$, Sr, and Ba; $Y=\mathrm{Au}$ and Hg; $Z=\mathrm{Sn}$, Pb, As, Sb, and Bi) through high-throughput ab initio screening. These new compounds exhibit ultralow lattice thermal conductivity ${\kappa }_L$ close to the theoretical minimum due to strong anharmonic rattling of the heavy noble metals, while preserving high power factors, thus resulting in excellent phonon-glass electron-crystal materials.