We study a charge two-channel Kondo model, demonstrating that recent experiments [Z. Iftikhar et al, Nature (London) 526, 233 (2015)] realize an essentially perfect quantum simulation—not just of its universal physics, but also nonuniversal effects away from the scaling limit. Numerical renormalization group (RG) calculations yield conductance line shapes encoding RG flow to a critical point involving a free Majorana fermion. By mimicking the experimental protocol, the experimental curve is reproduced quantitatively over 9 orders of magnitude, although we show that far greater bandwidth/temperature separation is required to obtain the universal result. Fermi liquid instabilities are also studied: In particular, our exact analytic results for nonlinear conductance provide predictions away from thermal equilibrium, in the regime of existing experiments.

Quantifying coherence is an essential endeavor for both quantum foundations and quantum technologies. Here, the robustness of coherence is defined and proven to be a full monotone in the context of the recently introduced resource theories of quantum coherence. The measure is shown to be observable, as it can be recast as the expectation value of a coherence witness operator for any quantum state. The robustness of coherence is evaluated analytically on relevant classes of states, and an efficient semidefinite program that computes it on general states is given. An operational interpretation is finally provided: the robustness of coherence quantifies the advantage enabled by a quantum state in a phase discrimination task.

The chiral anomaly provides smoking-gun evidence of a new confining gauge theory. Motivated by a reported event excess in a diphoton invariant mass distribution at the LHC, we discuss a scenario that a pseudo-Nambu-Goldstone (PNG) boson of a new QCD-like theory is produced by gluon fusion and decays into a pair of the standard model gauge bosons. Despite the strong dynamics, the production cross section and the decay widths are determined by an anomaly matching condition. The excess can be explained by the PNG boson with mass of around 750 GeV. The model also predicts exotic hadrons such as a color-octet scalar and baryons. Some of them are within the reach of the LHC experiment.

We construct a weakly coupled renormalizable model to explain the 750 GeV diphoton excess. The 750 GeV resonance [denoted as $X(750)$] is interpreted as a pseudoscalar coming from a complex singlet. The model also naturally provides a dark matter candidate. One of the most attractive feature of the model is that decays of $X(750)$ are all loop induced, so the diphoton rate is not diluted by unwanted tree level branching fractions. Relevant Yukawa interactions need not be tuned to the near-nonperturbative region to explain the rate. The model is highly predictive, including the pseudoscalar nature of $X(750)$ and two nearly mass-degenerate exotic quarks carrying electric charge $5/3$ and $2/3$, respectively. Rich phenomenology is expectedf with respect to collider searches, flavor physics, and dark matter detection, if $X(750)$ can be pinned down by future LHC experiments.

We interpret the diphoton excess recently reported by the ATLAS and CMS Collaborations as a new resonance arising from the sgoldstino scalar, which is the superpartner of the Goldstone mode of spontaneous supersymmetry breaking, the goldstino. The sgoldstino is produced at the LHC via gluon fusion and decays to photons, with interaction strengths proportional to the corresponding gaugino masses over the supersymmetry breaking scale. Fitting the excess, while evading bounds from searches in the dijet, $Z\gamma$, $ZZ$, and $WW$ final states, selects the supersymmetry breaking scale to be a few TeV and particular ranges for the gaugino masses. The two real scalars, corresponding to the $CP$-even and $CP$-odd parts of the complex sgoldstino, both have narrow widths, but their masses can be split of the order of 10–30 GeV by electroweak mixing corrections, which could account for the preference of a wider resonance width in the current low-statistics data. In the parameter space under consideration, tree level $F$-term contributions to the Higgs mass arise, in addition to the standard $D$-term contribution proportional to the $Z$-boson mass, which can significantly enhance the tree level Higgs mass.

We discuss nonstandard interpretations of the 750 GeV diphoton excess recently reported by the ATLAS and CMS Collaborations which do not involve a new, relatively broad resonance with a mass near 750 GeV. Instead, we consider the sequential cascade decay of a much heavier, possibly quite narrow, resonance into two photons along with one or more additional particles. The resulting diphoton invariant mass signal is generically rather broad, as suggested by the data. We examine three specific event topologies—the “antler,” the “sandwich,” and the two-step cascade decay—and show that they all can provide a good fit to the observed published data. In each case, we delineate the preferred mass parameter space selected by the best fit. In spite of the presence of extra particles in the final state, the measured diphoton $p_T$ spectrum is moderate due to its anticorrelation with the diphoton invariant mass. We comment on the future prospects of discriminating with higher statistics between our scenarios, as well as from more conventional interpretations.

We present the structural and magnetic properties of a new compound family, ${\mathrm{Mg}}_2{\mathrm{RE}}_3{\mathrm{Sb}}_3{\mathrm{O}}_{14}$ ($\mathrm{RE}=\mathrm{Gd},\mathrm{Dy},\mathrm{Er}$), with a hitherto unstudied frustrating lattice, the “tripod kagome" structure. Susceptibility (ac, dc) and specific heat exhibit features that are understood within a simple Luttinger-Tisza-type theory. For $\mathrm{RE}=\mathrm{Gd}$, we found long-ranged order (LRO) at 1.65 K, which is consistent with a 120° structure, demonstrating the importance of diople interactions for this 2D Heisenberg system. For $\mathrm{RE}=\mathrm{Dy}$, LRO at 0.37 K is related to the “kagome spin ice” physics for a 2D system. This result shows that the tripod kagome structure accelerates the transition to LRO predicted for the related pyrochlore systems. For $\mathrm{RE}=\mathrm{Er}$, two transitions, at 80 mK and 2.1 K are observed, suggesting the importance of quantum fluctuations for this putative $XY$ system.

Structurally coherent and chemically abrupt interfaces formed between polar and nonpolar perovskite oxides provide an ideal platform for examining the purely electronic reconstruction known as the polar catastrophe and the emergence of mobile or bound charges at the interface. The appearance of mobile charges induced by the polar catastrophe is already established in the ${\mathrm{LaAlO}}_3/{\mathrm{SrTiO}}_3$ heterojunctions. Although not experimentally verified, the polar catastrophe can also lead to the emergence of spontaneous polarization. We report that thin films of originally nonpolar ${\mathrm{LaFeO}}_3$ grown on ${\mathrm{SrTiO}}_3$ are converted to polar as a consequence of the polar catastrophe. The induced spontaneous polarization evokes photovoltaic properties distinct from conventional $p\text{−}n$ junctions, such as a switching of the photocurrent direction by changing the interfacial atomic sequence. The control of the bulk polarization by engineering the interface demonstrated here will expand the possibilities for designing and realizing new polar materials with photovoltaic functions.

We report on the emergence of two disconnected superconducting domes in alkali-metal potassium- (K-)doped FeSe ultrathin films grown on graphitized SiC(0001). The superconductivity exhibits hypersensitivity to K dosage in the lower-$T_{\mathrm{c}}$ dome, whereas in the heavily electron-doped higher-$T_{\mathrm{c}}$ dome it becomes spatially homogeneous and robust against disorder, supportive of a conventional Cooper-pairing mechanism. Furthermore, the heavily K-doped multilayer FeSe films all reveal a large superconducting gap of $\sim 14\mathrm{meV}$, irrespective of film thickness, verifying the higher-$T_{\mathrm{c}}$ superconductivity only in the topmost FeSe layer. The unusual finding of a double-dome superconducting phase is a step towards the mechanistic understanding of superconductivity in FeSe-derived superconductors.

We study a classical many-particle system with an external control represented by a time-dependent extensive parameter in a Lagrangian. We show that thermodynamic entropy of the system is uniquely characterized as the Noether invariant associated with a symmetry for an infinitesimal nonuniform time translation $t\to t+\eta \hslash \beta$, where $\eta$ is a small parameter, $\hslash$ is the Planck constant, $\beta$ is the inverse temperature that depends on the energy and control parameter, and trajectories in the phase space are restricted to those consistent with quasistatic processes in thermodynamics.

We demonstrate optomechanical quantum control of the internal electronic states of a diamond nitrogen-vacancy (NV) center in the resolved-sideband regime by coupling the NV to both optical fields and surface acoustic waves via a phonon-assisted optical transition and by taking advantage of the strong excited-state electron-phonon coupling of a NV center. Optomechanically driven Rabi oscillations as well as quantum interferences between the optomechanical sideband and the direct dipole-optical transitions are realized. These studies open the door to using resolved-sideband optomechanical coupling for quantum control of both the atomlike internal states and the motional states of a coupled NV-nanomechanical system, leading to the development of a solid-state analog of trapped ions.

Electron-phonon coupling is one of the most fundamental effects in condensed matter physics. We here demonstrate that photoelectron momentum mapping can reveal and visualize the coupling between specific vibrational modes and electronic excitations. When imaging molecular orbitals with high energy resolution, the intensity patterns of photoelectrons of the vibronic sidebands of molecular states show characteristic changes due to the distortion of the molecular frame in the vibronically excited state. By comparison to simulations, an assignment of specific vibronic modes is possible, thus providing unique information on the coupling between electronic and vibronic excitation.

We directly observe the quantum interference between two well-separated trapped-ion mechanical oscillator wave packets. The superposed state is created from a spin-motion entangled state using a heralded measurement. Wave packet interference is observed through the energy eigenstate populations. We reconstruct the Wigner function of these states by introducing probe Hamiltonians which measure Fock state populations in displaced and squeezed bases. Squeezed-basis measurements with 8 dB squeezing allow the measurement of interference for $\mathrm{\Delta }\alpha =15.6$, corresponding to a distance of 240 nm between the two superposed wave packets.

The same time domain structures (TDS) have been observed on two Magnetospheric Multiscale Satellites near Earth’s dayside magnetopause. These TDS, traveling away from the $X$ line along the magnetic field at $4000\mathrm{km}/\mathrm{s}$, accelerated field-aligned $\sim 5\mathrm{eV}$ electrons to $\sim 200\mathrm{eV}$ by a single Fermi reflection of the electrons by these overtaking barriers. Additionally, the TDS contained both positive and negative potentials, so they were a mixture of electron holes and double layers. They evolve in $\sim 10\mathrm{km}$ of space or 7 ms of time and their spatial scale size is 10–20 km, which is much larger than the electron gyroradius ($<1\mathrm{km}$) or the electron inertial length (4 km at the observation point, less nearer the $X$ line).

All quantum optomechanics experiments to date operate at cryogenic temperatures, imposing severe technical challenges and fundamental constraints. Here, we present a novel design of on-chip mechanical resonators which exhibit fundamental modes with frequencies $f$ and mechanical quality factors $Q_{\mathrm{m}}$ sufficient to enter the optomechanical quantum regime at room temperature. We overcome previous limitations by designing ultrathin, high-stress silicon nitride (${\mathrm{Si}}_3{\mathrm{N}}_4$) membranes, with tensile stress in the resonators’ clamps close to the ultimate yield strength of the material. By patterning a photonic crystal on the SiN membranes, we observe reflectivities greater than 99%. These on-chip resonators have remarkably low mechanical dissipation, with $Q_{\mathrm{m}}\sim {10}^8$, while at the same time exhibiting large reflectivities. This makes them a unique platform for experiments towards the observation of massive quantum behavior at room temperature.

We experimentally study the effects of coupling one-dimensional many-body localized systems with identical disorder. Using a gas of ultracold fermions in an optical lattice, we artificially prepare an initial charge density wave in an array of 1D tubes with quasirandom on-site disorder and monitor the subsequent dynamics over several thousand tunneling times. We find a strikingly different behavior between many-body localization and Anderson localization. While the noninteracting Anderson case remains localized, in the interacting case any coupling between the tubes leads to a delocalization of the entire system.

The nanoscopic structure of the cores of topological defects in anisotropic condensed matter is an unresolved issue, although a number of theoretical predictions have been reported. In the experimental study reported in this Letter, we template the assembly of amphiphilic molecules from the cores of defects in liquid crystals and thereby provide the first experimental evidence that the cores of singular defects that appear optically to be points (with strength $m=+1$) are nanometer-sized closed-loop, disclination lines. We also analyze this result in the context of a model that describes the influence of amphiphilic assemblies on the free energy and stability of the defects. Overall, our experimental results and theoretical predictions reveal that the cores of defects with opposite strengths (e.g., $m=+1$ vs $m=-1$) differ in ways that profoundly influence processes of molecular self-assembly.

Smectic liquid crystals are remarkable, beautiful examples of materials microstructure, with ordered patterns of geometrically perfect ellipses and hyperbolas. The solution of the complex problem of filling three-dimensional space with domains of focal conics under constraining boundary conditions yields a set of strict rules, which are similar to the compatibility conditions in a martensitic crystal. Here we present the rules giving compatible conditions for the concentric circle domains found at two-dimensional smectic interfaces with planar boundary conditions. Using configurations generated by numerical simulations, we develop a clustering algorithm to decompose the planar boundaries into domains. The interfaces between different domains agree well with the smectic compatibility conditions. We also discuss generalizations of our approach to describe the full three-dimensional smectic domains, where the variant symmetry group is the Weyl-Poincaré group of Lorentz boosts, translations, rotations, and dilatations.

We first show that the currently accepted statistical mechanics for granular matter is flawed. The reason is that it is based on the volume function, which depends only on a minute fraction of all the structural degrees of freedom and is unaffected by most of the configurational microstates. Consequently, the commonly used partition function underestimates the entropy severely. We then propose a new formulation, replacing the volume function with a connectivity function that depends on all the structural degrees of freedom and accounts correctly for the entire entropy. We discuss the advantages of the new formalism and derive explicit results for two- and three-dimensional systems. We test the formalism by calculating the entropy of an experimental two-dimensional system, as a function of system size, and showing that it is an extensive variable.

We present the measurement of the transverse single-spin asymmetry of weak boson production in transversely polarized proton-proton collisions at $\sqrt{s}=500\mathrm{GeV}$ by the STAR experiment at RHIC. The measured observable is sensitive to the Sivers function, one of the transverse-momentum-dependent parton distribution functions, which is predicted to have the opposite sign in proton-proton collisions from that observed in deep inelastic lepton-proton scattering. These data provide the first experimental investigation of the nonuniversality of the Sivers function, fundamental to our understanding of QCD.