We study the interplay between disorder and interaction in one-dimensional topological superconductors which carry localized Majorana zero-energy states. Using Abelian bosonization and the perturbative renormalization group approach, we obtain the renormalization group flow and the associated scaling dimensions of the parameters and identify the critical points of the low-energy theory. We predict a quantum phase transition from a topological superconducting phase to a nontopological localized phase, and obtain the phase boundary between these two phases as a function of the electron-electron interaction and the disorder strength in the nanowire. Based on an instanton analysis which incorporates the effect of disorder, we also identify a large regime of stability of the Majorana-carrying topological phase in the parameter space of the model.

We show that by magnetically trapping a superconducting microsphere close to a quantum circuit, it is possible to perform ground-state cooling and prepare quantum superpositions of the center-of-mass motion of the microsphere. Due to the absence of clamping losses and time-dependent electromagnetic fields, the mechanical motion of micrometer-sized metallic spheres in the Meissner state is predicted to be very well isolated from the environment. Hence, we propose to combine the technology of magnetic microtraps and superconducting qubits to bring relatively large objects to the quantum regime.

Engineering nanomechanical quantum systems possessing ultralong motional coherence times allows for applications in precision quantum sensing and quantum interfaces, but to achieve ultrahigh motional $Q$ one must work hard to remove all forms of motional noise and heating. We examine a magneto-meso-mechanical quantum system that consists of a 3D arrangement of miniature superconducting loops which is stably levitated in a static inhomogeneous magnetic field. The motional decoherence is predominantly due to loss from induced eddy currents in the magnetized sphere which provides the trapping field ultimately yielding $Q\sim {10}^9$ with motional oscillation frequencies of several hundreds of kilohertz. By inductively coupling this levitating object to a nearby driven flux qubit one can cool its motion very close to the ground state and this may permit the generation of macroscopic entangled motional states of multiple clusters.

We present a study of the proximity effect between a ferromagnet and a paramagnetic metal of varying disorder. Thin beryllium films are deposited onto a 5 nm thick layer of the ferromagnetic insulator EuS. This bilayer arrangement induces an exchange field, $H_{\mathrm{ex}}$, of a few tesla in low-resistance Be films with sheet resistance $R\ll R_Q$, where $R_Q=h/e^2$ is the quantum resistance. We show that $H_{\mathrm{ex}}$ survives in very high-resistance films and, in fact, appears to be relatively insensitive to the Be disorder. We exploit this fact to produce a giant low-field magnetoresistance in the correlated-insulator phase of Be films with $R\gg R_Q$.

We introduce a Monte Carlo scheme based on sampling of Pfaffians to investigate Anderson’s resonating-valence-bond (RVB) spin liquid wave function on the kagome and the triangular lattice. This eliminates a sign problem that prevents utilization of the valence bond basis in Monte Carlo studies for nonbipartite lattices. Studying lattice sizes of up to 600 sites, we calculate singlet-singlet and spin-spin correlations and demonstrate how the lattice symmetry is restored within each topological sector as the system size is increased. Our findings are consistent with the expectation that the nearest-neighbor RVB states describe a topological spin liquid on these nonbipartite lattices.

Resonating valence bond (RVB) states are of crucial importance in our intuitive understanding of quantum spin liquids in 2D. We systematically classify short-range bosonic RVB states into symmetric or nematic spin liquids by examining their flux patterns. We further map short-range bosonic RVB states into projected BCS wave functions, on which we perform large-scale Monte Carlo simulations without the minus sign problem. Our results clearly show that both spin and dimer correlations decay exponentially in all the short-range frustrated (nonbipartite or $Z_2$) bosonic RVB states we studied, indicating that they are gapped $Z_2$ quantum spin liquids. Generically, we conjecture that all short-range frustrated bosonic RVB states in 2D have only short-range correlations.

We show that spin-orbit coupling (SOC) gives rise to pairing instability in a highly polarized two-dimensional Fermi gas for an arbitrary interaction strength. The pairing instability can lead to a Fulde-Ferrell-Larkin-Ovchinnikov-like molecular state, which undergoes a first-order transition into a pairing state with zero center-of-mass momentum as the parameters are tuned. These pairing states are metastable against a polaron state dressed by particle-hole fluctuations for small SOC. At large SOC, a polaron-molecule transition exists, which suggests a phase transition between the topological superfluid state and the normal state for a highly polarized Fermi gas in the thermodynamic limit. As polarization in a Fermi gas with SOC is induced by the effective Zeeman field, we also discuss the influences of the effective Zeeman field on the ground state of the system. Our findings may be tested directly in future experiments.

Quantum or torsion gravity models predict unusual properties of space-time at very short distances. In particular, near the Planck length, around ${10}^{-35}\mathrm{m}$, empty space may behave as a crystal, singly or doubly refractive. However, this hypothesis remains uncheckable for any direct measurement, since the smallest distance accessible in experiment is about ${10}^{-19}\mathrm{m}$ at the LHC. Here I propose a laboratory test to measure the space refractivity and birefringence induced by gravity. A sensitivity from ${10}^{-31}\mathrm{m}$ down to the Planck length could be reached at existent GeV and future TeV energy lepton accelerators using laser Compton scattering. There are already experimental hints for gravity signature at distances approaching the Planck length by 5–7 orders of magnitude, derived from SLC and HERA data.

We show how constraints on the time integrated event rate from a given dark matter (DM) direct detection experiment can be used to bound the amplitude of the annual modulation signal in another experiment. The method requires only mild assumptions about the properties of the local DM distribution: that it is temporally stable on the scale of months and spatially homogeneous on the ecliptic. We apply the method to the annual modulation signal in DAMA/LIBRA, which we compare to the bounds derived from XENON10, XENON100, cryogenic DM search, and SIMPLE data. Assuming a DM mass of 10 GeV, we show that under the above assumptions about the DM halo, a DM interpretation of the DAMA/LIBRA signal is excluded for several classes of models: at $6.3\sigma$ ($4.6\sigma$) for elastic isospin conserving (violating) spin-independent interactions, and at $4.9\sigma$ for elastic spin-dependent interactions on protons.

This paper introduces an experimental probe of the sterile neutrino with a novel, high-intensity source of electron antineutrinos from the production and subsequent decay of ${}^8\mathrm{Li}$. When paired with an existing $\sim 1$ kton scintillator-based detector, this $⟨E_{\nu }⟩=6.4$ MeV source opens a wide range of possible searches for beyond standard model physics via studies of the inverse beta decay interaction ${\overline{\nu }}_e+p\to e^{+}+n$. In particular, the experimental design described here has unprecedented sensitivity to ${\overline{\nu }}_e$ disappearance at $\Delta m^2\sim 1{\mathrm{eV}}^2$ and features the ability to distinguish between the existence of zero, one, and two sterile neutrinos.

Molecular frame high-harmonic spectra of aligned ${\mathrm{N}}_2$ molecules reveal a Cooper-like minimum. By deconvolving the laboratory frame alignment distribution, what was previously thought to be a maximum of emission along the molecular axis is found to be maxima at 35 degrees off axis, with a spectral minimum on axis. Both of these features are supported by photoionization calculations that underline the relationship between high-harmonic spectroscopy and photoionization measurements. The calculations reveal that the on axis spectral minimum is a Cooper-like minimum that arises from the destructive interference of the $p$ and $f$ partial wave contributions to high-harmonic photorecombination. Features such as Cooper minima and shape resonances are ubiquitous in molecular photoionization or recombination.

Nonlinear frequency conversion is a well known and widely exploited family of effects in optics, often arising from a Kerr nonlinearity in a crystal medium. Here, we report high stability frequency conversion in the microwave regime due to a ${\chi }^{(3)}$ nonlinearity in sapphire introduced by a dilute concentration of paramagnetic spins. First, we produce a high stability comb from two microwave fields at 12.029 and 12.037 GHz corresponding to two high $Q$-factor whispering gallery (WG) modes within the electron spin resonance bandwidth of the ${\mathrm{Fe}}^{3+}$ ion. The resulting comb is generated by a cascaded four-wave mixing effect with a 7.7 MHz repetition rate. Then, by suppressing four-wave mixing by increasing the threshold power, third harmonic generation is achieved in a variety of WG modes coupled to various species of paramagnetic ion within the sapphire.

We demonstrate that almost 100% of incident photons can interact with a monolayer of scatterers in a symmetrical environment. Nearly perfect optical extinction through free-standing transparent nanorod arrays has been measured. The sharp spectral opacity window, in the form of a characteristic Fano resonance, arises from the coherent multiple scattering in the array. In addition, we show that nanorods made of absorbing material exhibit a 25-fold absorption enhancement per unit volume compared to unstructured thin film. These results open new perspectives for light management in high-$Q$, low volume dielectric nanostructures, with potential applications in optical systems, spectroscopy, and optomechanics.

The proposal of simultaneously determining the hohlraum peak radiation temperature $T_R$ and $M$-band fraction $f_M$ by shock velocity measurement technique [Y. S. Li et al. Phys. Plasmas 18, 022701 (2011)] is demonstrated for the first time in recent experiments conducted on SGIII-prototype laser facility. In the experiments, $T_R$ and $f_M$ are determined by using the observed shock velocities in Al and Ti. For the Au hohlraum used in the experiments, $T_R$ is about 160 eV and $f_M$ is around 4.3% under a 1 ns laser pulse of 2 kJ. The results from this method are complementary to those from the broadband x-ray spectrometer, and the technique can be further used to determine $T_R$ and $f_M$ inside an ignition hohlraum.

The orthorhombic boride crystal family $XY{\mathrm{B}}_{14}$, where $X$ and $Y$ are metal atoms, plays a critical role in a unique class of superhard compounds, yet there have been no studies aimed at understanding the origin of the mechanical strength of this compound. We present here the results from a comprehensive investigation into the fracture strength of the archetypal ${\mathrm{AlLiB}}_{14}$ crystal. First principles, ab initio, methods are used to determine the ideal brittle cleavage strength for several high-symmetry orientations. The elastic tensor and the orientation-dependent Young’s modulus are calculated. From these results the lower bound fracture strength of ${\mathrm{AlLiB}}_{14}$ is predicted to be between 29 and 31 GPa, which is near the measured hardness reported in the literature. These results indicate that the intrinsic strength of ${\mathrm{AlLiB}}_{14}$ is limited by the interatomic B-B bonds that span between the B layers.

The isostructural $\alpha \mathrm{\text{−}}\gamma$ phase transition in cerium is analyzed using density-functional theory with different exchange-correlation functionals, in particular the PBE0 hybrid functional and the exact-exchange plus correlation in the random-phase approximation [$(\mathrm{EX}+\mathrm{cRPA})@\mathrm{PBE}0$] approach. We show that the Hartree-Fock exchange part of the hybrid functional gives rise to two distinct solutions at zero temperature that can be associated with the $\alpha$ and $\gamma$ phases of cerium. However, despite the relatively good structural and magnetic properties, PBE0 predicts the $\gamma$ phase to be the stable phase at ambient pressure and zero temperature, in contradiction with low temperature experiments. $\mathrm{EX}+\mathrm{cRPA}$ reverses the energetic ordering, which emphasizes the importance of correlation for rare-earth systems.

Full electric-field control of spin orientations is one of the key tasks in semiconductor spintronics. We demonstrate that electric-field pulses can be utilized for phase-coherent $\pm \pi$ spin rotation of optically generated electron spin packets in InGaAs epilayers detected by time-resolved Faraday rotation. Through spin-orbit interaction, the electric-field pulses act as local magnetic field pulses. By the temporal control of the local magnetic field pulses, we can turn on and off electron spin precession and thereby rotate the spin direction into arbitrary orientations in a two-dimensional plane. Furthermore, we demonstrate a spin-echo-type spin drift experiment and find an unexpected partial spin rephasing, which is evident by a doubling of the spin dephasing time.

We argue that parametrically strong enhancement of a thermoelectric current can be observed in conventional superconductors doped by magnetic impurities. This effect is caused by the violation of the symmetry between electronlike and holelike excitations due to formation of subgap bound Andreev states in the vicinity of magnetic impurities. We develop a quantitative theory of this effect and demonstrate that it can be detected in modern experiments.

We report the molecular dipole effect on conduction electrons in the title superconductor. The angular-dependent magnetoresistance has a peak for fields nearly parallel to the conducting layer, and the peak width scales as the field component perpendicular to the layer, indicating incoherent interlayer transport. However, two closed Fermi surfaces are observed in quantum oscillation. Accordingly, crystallographically independent layers have different charge densities in a bulk single crystal. The electric dipole of tetrahydrofuran gives rise to interlayer charge disproportionation.

We study three-terminal charge transport through individual ${\mathrm{Fe}}_4$ single-molecule magnets. Magnetic anisotropy of the single molecule is directly observed by introducing a spectroscopic technique based on measuring the position of the degeneracy point as a function of gate voltage and applied magnetic field. A nonlinear field-dependence is observed which changes by rotating the sample and is, thus, a direct proof of magnetic anisotropy. The sensitivity of this method allows us to observe small changes in the orientation and magnitude of the anisotropy in different charge states. We find that the easy axes in adjacent states are (almost) collinear.