We provide a detailed explanation of the formalism necessary to construct matrix product states for non-Abelian quasiholes in fractional quantum Hall model states. Our construction yields an efficient representation of the wave functions with conformal-block normalization and monodromy, and complements the matrix product state representation of fractional quantum Hall ground states.

The sign problem is the fundamental limitation to quantum Monte Carlo simulations of the statistical mechanics of interacting fermions. Determinant quantum Monte Carlo (DQMC) is one of the leading methods to study lattice fermions, such as the Hubbard Hamiltonian, which describe strongly correlated phenomena including magnetism, metal-insulator transitions, and possibly exotic superconductivity. Here, we provide a comprehensive dataset on the geometry dependence of the DQMC sign problem for different densities, interaction strengths, temperatures, and spatial lattice sizes. We supplement these data with several observations concerning general trends in the data, including the dependence on spatial volume and how this can be probed by examining decoupled clusters, the scaling of the sign in the vicinity of a particle-hole symmetric point, and the correlation between the total sign and the signs for the individual spin species.

The semimetal to antiferromagnet quantum phase transition of the Hubbard model on the honeycomb lattice has come to the forefront in the context of the proposal that a semimetal to spin liquid transition can occur before the transition to the antiferromagnetic phase. To study the semimetal to antiferromagnet transition, we generalize the two-particle self-consistent (TPSC) approach to the honeycomb lattice (a structure that can be realized in graphene for example). We show that the critical interaction strength where the transition occurs is $U_c/t=3.79\pm 0.01$, quite close to the value $U_c/t=3.869\pm 0.013$ reported using large-scale quantum Monte Carlo simulations. This reinforces the conclusion that the semimetal to spin-liquid transition is preempted by the transition to the antiferromagnet. Since TPSC satisfies the Mermin-Wagner theorem, we find temperature-dependent results for the antiferromagnetic and ferromagnetic correlation lengths as well as the dependence of double occupancy and of the renormalized spin and charge interactions on the bare interaction strength. We also estimate the value of the crossover temperature to the renormalized classical regime as a function of interaction strength.

Here we study the effect of La-doping in EuO thin films using superconducting quantum interference device magnetometry, muon spin rotation $(\mu \mathrm{SR})$, polarized neutron reflectivity (PNR), and density functional theory (DFT). The $\mu \mathrm{SR}$ data shows that the ${\mathrm{La}}_{0.15}{\mathrm{Eu}}_{0.85}\mathrm{O}$ is homogeneously magnetically ordered up to its elevated $T_{\mathrm{C}}$. It is concluded that bound magnetic polaron behavior does not explain the increase in $T_{\mathrm{C}}$ and an Ruderman-Kittel-Kasuya-Yosida-like (RKKY-like) interaction is consistent with the $\mu \mathrm{SR}$ data. The estimation of the magnetic moment by DFT simulations concurs with the results obtained by PNR, showing a reduction of the magnetic moment per ${\mathrm{La}}_x{\mathrm{Eu}}_{1-x}\mathrm{O}$ for increasing lanthanum doping. This reduction of the magnetic moment is explained by the reduction of the number of Eu-$4f$ electrons present in all the magnetic interactions in EuO films. Finally, we show that an upwards shift of the Fermi energy with La or Gd doping gives rise to half-metallicity for doping levels as high as 3.2%.

We investigate the strong-coupling regime of a self-assembled quantum dot in a tunable microcavity with dark-field laser spectroscopy. The high quality of the spectra allows the line shapes to be analyzed revealing subtle quantum interferences. Agreement with a model calculation is achieved only by including exciton dephasing which reduces the cooperativity from a bare value of 9.0 to the time-averaged value 5.5. In the pursuit of high cooperativity, besides a high Q and low mode-volume cavity, we demonstrate that equal efforts need to be taken towards lifetime-limited emitter linewidths.

We explore theoretically the formation of bound states in the continuum (BICs) in graphene hosting two collinear adatoms situated at different sides of the sheet and at the center of the hexagonal cell, where a phantom atom of a fictitious lattice emulates the six carbons of the cell. We verify that in this configuration the local density of states near the Dirac points exhibits two characteristic features: (i) a cubic dependence on energy instead of a linear one for graphene as found in New J. Phys. 16, 013045 (2014), and (ii) the formation of BICs as an aftermath of a Fano destructive interference assisted by the Coulomb correlations in the adatoms. For the geometry where adatoms are collinear to carbon atoms, we report an absence of BICs.

Recent papers by S. A. Mikhailov [Phys. Rev. B 83, 155303 (2011) and Phys. Rev. B 89, 045410 (2014)] claim to explain “all experimental facts” pertinent to microwave-induced resistance oscillations and zero-resistance states in terms of “the ponderomotive force theory.” This Comment shows that the analysis of the results obtained in the above-mentioned papers, in fact, leads to opposite conclusions, i.e., that they cannot explain even the most basic experimental facts.

We show that all questions raised in the Comment can be easily answered within the theory formulated in the commented papers. It is also shown that the bulk theory promoted by the commenter fails to explain the most important fundamental features of the discussed phenomenon.

The physical state and properties of silicates at conditions encountered in the cores of gas giants, ice giants, and of Earth-like exoplanets now discovered with masses up to several times the mass of the Earth remain mostly unknown. Here, we report on theoretical predictions of the properties of silica, ${\text{SiO}}_2$, up to 4 TPa and about 20 000 K by using first principles molecular dynamics simulations based on density functional theory. For conditions found in the super Earths and in ice giants, we show that silica remains a poor electrical conductor up to 10 Mbar due to an increase in the Si-O coordination with pressure. For Jupiter and Saturn cores, we find that ${\text{MgSiO}}_3$ silicate has not only dissociated into MgO and ${\text{SiO}}_2$, as shown in previous studies, but that these two phases have likely differentiated to lead to a core made of liquid ${\text{SiO}}_2$ and solid (Mg,Fe)O.

Data-driven approaches are particularly useful for computational materials discovery and design as they can be used for rapidly screening over a very large number of materials, thus suggesting lead candidates for further in-depth investigations. A central challenge of such approaches is to develop a numerical representation, often referred to as a fingerprint, of the materials. Inspired by recent developments in cheminformatics, we propose a class of hierarchical motif-based topological fingerprints for materials composed of elements such as C, O, H, N, F, etc., whose coordination preferences are well understood. We show that these fingerprints, when representing either molecules or crystals, may be effectively mapped onto a variety of properties using a similarity-based learning model and hence can be used to predict the relevant properties of a material, given that its fingerprint can be defined. Two simple machine-learning-based procedures are introduced to demonstrate that the learning model can be inverted to identify the desired fingerprints and then to reconstruct molecules which possess a set of targeted properties.

We investigate what happens if an Anderson localized system is coupled to a small bath, with a discrete spectrum, when the coupling between system and bath is specially chosen so as to never localize the bath. We find that the effect of the bath on localization in the system is a nonmonotonic function of the coupling between system and bath. At weak couplings, the bath facilitates transport by allowing the system to “borrow” energy from the bath. But, above a certain coupling the bath produces localization because of an orthogonality catastrophe, whereby the bath “dresses” the system and hence suppresses the hopping matrix element. We call this last regime the regime of “Zeno localization” since the physics of this regime is akin to the quantum Zeno effect, where frequent measurements of the position of a particle impede its motion. We confirm our results by numerical exact diagonalization.

We show theoretically by numerically solving the Landau-Lifshitz-Gilbert equation with a classical spin model on a two-dimensional system that both magnetic skyrmions and skyrmion lattices can be moved with microwave magnetic fields. The mechanism is enabled by breaking the axial symmetry of the skyrmion, for example, through application of a static in-plane external field. The net velocity of the skyrmion depends on the frequency and amplitude of the microwave fields as well as the strength of the in-plane field. The maximum velocity is found where the frequency of the microwave coincides with the resonance frequency of the breathing mode of the skyrmions.

Spin wave spectra of ultrathin epitaxial cobalt films deposited on W(110), Cu(111), and Au(111) surfaces are studied in the wave-vector regime between $0.1{\AA }^{-1}$ and $0.7{\AA }^{-1}$ using inelastic electron scattering with 6 meV energy resolution. Up to three different spin wave modes are resolved for wave vectors $q_{\parallel }<0.35{\AA }^{-1}$. The modes are identified as the acoustic mode and standing modes with one and two nodes inside the film. The relative weight of the modes in a particular spectrum may depend critically on the electron impact energy. For larger wave vectors beyond $q_{\parallel }>0.35{\AA }^{-1}$ and layers thicker than five atom layers the separate modes merge into a single, broad loss feature. Since the shape and position of the loss feature depend on the electron impact energy, a separation into different modes is nevertheless possible for not too large wave vectors. The spin wave dispersion curves of films grown on W(110) agree with those observed on Cu(111) if one takes into account that on copper the cobalt grows in islands so that the mean height of the islands is higher than the nominal coverage. On films grown on Au(111) the low wave vector spin waves are buried in the high elastic diffuse scattering caused by the considerable disorder in the films. The broader appearance of the spectra at higher wave vectors compared to films grown on W(110) and Cu(111) is quantitatively accounted for by disorder-induced kinematic broadening. Because of the granular growth on copper and gold primarily the spin wave spectrum of cobalt films on W(110) is amenable to quantitative theoretical analysis. Such an analysis is not available at present. We show however, that the dispersion curves are incompatible with the Heisenberg model as long as only a single, layer-independent exchange coupling constant is invoked.

The Hubbard model with local on-site repulsion is generally thought to possess a superconducting ground state for appropriate parameters, but the effects of more realistic long-range Coulomb interactions have not been studied extensively. We study the influence of these interactions on superconductivity by including nearest- and next-nearest-neighbor extended Hubbard interactions in addition to the usual on-site terms. Utilizing numerical exact diagonalization, we analyze the signatures of superconductivity in the ground states through the fidelity metric of quantum information theory. We find that nearest and next-nearest neighbor interactions have thresholds above which they destabilize superconductivity regardless of whether they are attractive or repulsive, seemingly due to competing charge fluctuations.

We calculate the effect of a heat current on transporting ${}^3\mathrm{He}$ dissolved in superfluid ${}^4\mathrm{He}$ at ultralow concentration, as will be utilized in a proposed experimental search for the electric dipole moment of the neutron (nEDM). In this experiment, a phonon wind will be generated to drive (partly depolarized) ${}^3\mathrm{He}$ down a long pipe. In the regime of ${}^3\mathrm{He}$ concentrations $\lesssim {10}^{-9}$ and temperatures $\sim 0.5$ K, the phonons comprising the heat current are kept in a flowing local equilibrium by small angle phonon-phonon scattering, while they transfer momentum to the walls via the ${}^4\mathrm{He}$ first viscosity. On the other hand, the phonon wind drives the ${}^3\mathrm{He}$ out of local equilibrium via phonon-${}^3\mathrm{He}$ scattering. For temperatures below $0.5$ K, both the phonon and ${}^3\mathrm{He}$ mean free paths can reach the centimeter scale, and we calculate the effects on the transport coefficients. We derive the relevant transport coefficients, the phonon thermal conductivity, and the ${}^3\mathrm{He}$ diffusion constants from the Boltzmann equation. We calculate the effect of scattering from the walls of the pipe and show that it may be characterized by the average distance from points inside the pipe to the walls. The temporal evolution of the spatial distribution of the ${}^3\mathrm{He}$ atoms is determined by the time dependent ${}^3\mathrm{He}$ diffusion equation, which describes the competition between advection by the phonon wind and ${}^3\mathrm{He}$ diffusion. As a consequence of the thermal diffusivity being small compared with the ${}^3\mathrm{He}$ diffusivity, the scale height of the final ${}^3\mathrm{He}$ distribution is much smaller than that of the temperature gradient. We present exact solutions of the time dependent temperature and ${}^3\mathrm{He}$ distributions in terms of a complete set of normal modes.

We introduce a tunneling effect by a driving field, referred to as coherent revival of tunneling (CRT), corresponding to complete tunneling (transmission coefficient $=1$) that is revived from the circumstance of total reflection (transmission coefficient $\approx 0$) through application of an appropriate perpendicular high-frequency ac field. To illustrate CRT, we simulate electron transport through fish-bone-like quantum-dot arrays by using single-particle Green's functions along with Floquet theory, and we explore the corresponding current-field amplitude characteristics as well as current-polarization characteristics. In regard to the two characteristics, we show that CRT exhibits entirely different features than coherent destruction of tunneling and photon-assisted tunneling. We also discuss two practical conditions for experimental realization of CRT.