Motivated by the recently established duality between elasticity of crystals and a fracton tensor gauge theory, we combine it with boson-vortex duality, to explicitly account for bosonic statistics of the underlying atoms. We thereby derive a hybrid vector-tensor gauge dual of a supersolid, which features both crystalline and superfluid order. The gauge dual describes a fracton state of matter with full dipole mobility endowed by the superfluid order, as governed by “mutual” axion electrodynamics between the fracton and vortex sectors of the theory, with an associated generalized Witten effect. Vortex condensation restores $U(1)$ symmetry, confines dipoles to be subdimensional (recovering the dislocation glide constraint of a commensurate quantum crystal), and drives a phase transition between two distinct fracton phases. Meanwhile, condensation of elementary fracton dipoles and charges, respectively, provide a gauge dual description of the superhexatic and ordinary superfluid. Consistent with conventional wisdom, in the absence of crystalline order, $U(1)$-symmetric phases are prohibited at zero temperature via a mechanism akin to deconfined quantum criticality.

Polar and highly mobile domain walls in ${\mathrm{SrTiO}}_3$ move under electric and elastic fields. Two vastly different timescales dominate their dynamical behavior. The previously observed fast changes lead to anomalies near 40 K where the elastic moduli soften and the polarity of the walls becomes strong. Keeping the sample under isothermal conditions leads to a new and unexpected phenomenon: The softening vanishes over timescales of days while the piezoelectricity of the sample remains unchanged. The hardening follows glass dynamics below an onset at $T^{*}\approx 40\mathrm{K}$. The timescale of the hardening is strongly temperature dependent and can be followed experimentally down to 34 K when the relaxation is not completed within two days. The relaxation time of a stretched exponential decay increases exponentially with the decreasing temperature. This relaxation process follows similar dynamics after zero-field cooling and after applying or removing an electric field. The sluggish behavior is attributed to collective interactions of domain patterns following overdamped glass dynamics rather than ballistic dynamics.

We study stability of the Sachdev-Ye-Kitaev (${\mathrm{SYK}}_4$) model with a large but finite number of fermions $N$ with respect to a perturbation, quadratic in fermionic operators. We develop analytic perturbation theory in the amplitude of the ${\mathrm{SYK}}_2$ perturbation and demonstrate stability of the ${\mathrm{SYK}}_4$ infrared asymptotic behavior characterized by a Green function $G(\tau )\propto 1/{\tau }^{3/2}$, with respect to weak perturbation. This result is supported by exact numerical diagonalization. Our results open the way to build a theory of non-Fermi-liquid states of strongly interacting fermions.

In systems with competing interactions, continuous degeneracies can appear which are accidental, in that they are not related to any symmetry of the Hamiltonian. Accordingly, the pseudo-Goldstone modes associated with these degeneracies are also unprotected. Indeed, through a process known as “order-by-quantum disorder,” quantum zero-point fluctuations can lift the degeneracy and induce a gap for these modes. We show that this gap can be exactly computed at leading order in $1/S$ in spin-wave theory from the mean curvature of the classical and quantum zero-point energies—without the need to consider any spin-wave interactions. We confirm this equivalence through direct calculations of the spin-wave spectrum to $O(1/S^2)$ in a wide variety of theoretically and experimentally relevant quantum spin models. We prove this equivalence through the use of an exact sum rule that provides the required mixing of different orders of $1/S$. Finally, we discuss some implications for several leading order-by-quantum-disorder candidate materials, clarifying the expected pseudo-Goldstone gap sizes in ${\mathrm{Er}}_2{\mathrm{Ti}}_2{\mathrm{O}}_7$ and ${\mathrm{Ca}}_3{\mathrm{Fe}}_2{\mathrm{Ge}}_3{\mathrm{O}}_{12}$.

We show that a fixed set of woven defect lines in a nematic liquid crystal supports a set of nonsingular topological states which can be mapped on to recurrent stable configurations in the Abelian sandpile model or chip-firing game. The physical correspondence between local skyrmion flux and sandpile height is made between the two models. Using a toy model of the elastic energy, we examine the structure of energy minima as a function of topological class and show that the system admits domain wall skyrmion solitons.

Clustering is often presumed to lead to enhanced agglomeration between cohesive grains due to the reduced relative velocities of particles within a cluster. Our discrete-particle simulations on gravity-driven, gas-solid flows of cohesive grains exhibit the opposite trend, revealing a new mechanism we coin “cluster-induced deagglomeration.” Specifically, we examine relatively dilute gas-solid flows and isolate agglomerates of cohesive origin from overall heterogeneities in the system, i.e., agglomerates of cohesive origin and clusters of hydrodynamic origin. We observe enhanced clustering with an increasing system size (as is the norm for noncohesive systems) as well as reduced agglomeration. The reduced agglomeration is traced to the increased collisional impact velocities of particles at the surface of a cluster; i.e., higher levels of clustering lead to larger relative velocities between the clustered and nonclustered regions, thereby serving as an additional source of granular temperature. This physical picture is further evidenced by a theoretical model based on a balance between the generation and breakage rates of agglomerates. Finally, cluster-induced deagglomeration also provides an explanation for a surprising saturation of agglomeration levels in gravity-driven, gas-solid systems with increasing levels of cohesion, as opposed to the monotonically increasing behavior seen in free-evolving or driven granular systems in the absence of gravity. Namely, higher cohesion leads to more energy dissipation, which is associated with competing effects: enhanced agglomeration and enhanced clustering, the latter of which results in more cluster-induced deagglomeration.

Immune cells learn about their antigenic targets using tactile sense: a self-organized motif named immunological synapse forms between an immune cell and an antigen-presenting cell (APC) during recognition. Via synapses, immune cells apply mechanical pulling forces to selectively extract antigen (Ag) from APCs. Curiously, depending on its stage of development, a B lymphocyte exhibits distinct synaptic patterns and uses force at different strength and timing, which appears to strongly impact its ability to distinguish Ag affinities. We use a statistical-mechanical model to study how the experimentally observed synaptic architectures can originate from normal cytoskeletal forces coupled to the lateral organization of mobile receptors, and show how this active regulation scheme, collective in nature, may enhance the efficiency and capacity of discrimination.

We propose a search for Higgs decays with as many as 8 leptons in the final state. This signal can arise in a simple model with a hidden vector ($A_d$) that gets mass via a hidden scalar ($h_d$) vacuum expectation value. The 125 GeV Higgs boson can then decay $H\to h_d{h}_d\to 4A_d\to 8f$, where $f$ are standard model fermions. We recast current searches and show that a branching ratio (BR) of $H\to h_d{h}_d$ as large as 10% is allowed. We also describe a dedicated search that could place bounds on $\mathrm{BR}(H\to h_d{h}_d)$ as low as ${10}^{-5}$ using only $36{\mathrm{fb}}^{-1}$ of data, with significant improvements coming from greater integrated luminosity.

Currents driven by radio frequency (rf) waves in the interior of magnetic islands can stabilize deleterious tearing modes in tokamaks. Present analyses of stabilization assume that the local electron acceleration is unaffected by the presence of the island. However, the power deposition and electron acceleration are sensitive to the perturbation of the temperature. The nonlinear feedback on the power deposition in the island increases the temperature perturbation, and can lead to a bifurcation of the solution to the steady-state heat diffusion equation. The combination of the nonlinearly enhanced temperature perturbation with the rf current drive sensitivity to the temperature leads to an rf current condensation effect, which can increase the efficiency of rf current drive stabilization and reduce its sensitivity to radial misalignment of the ray trajectories. The threshold for the effect is in a regime that has been encountered in experiments, and will likely be encountered in ITER.

Pressure-induced formation of amorphous ices and the low-density amorphous (LDA) to high-density amorphous (HDA) transition have been believed to occur kinetically below a crossover temperature ($T_c$) above which thermodynamically driven crystalline-crystalline (e.g., ice ${\mathrm{I}}_h$-to-II) transitions and crystallization of HDA and LDA are dominant. Here we show compression-rate-dependent formation of a high-density noncrystalline (HDN) phase transformed from ice ${\mathrm{I}}_c$ above $T_c$, bypassing crystalline-crystalline transitions under rapid compression. Rapid decompression above $T_c$ transforms HDN to a low-density noncrystalline (LDN) phase which crystallizes spontaneously into ice ${\mathrm{I}}_c$, whereas slow decompression of HDN leads to direct crystallization. The results indicate the formation of HDA and the HDN-to-LDN transition above $T_c$ are results of competition between (de)compression rate, energy barrier, and temperature. The crossover temperature is shown to have an exponential relationship with the threshold compression rate. The present results provide important insight into the dynamic property of the phase transitions in addition to the static study.

Structural phase transitions and soft phonon modes pose a long-standing challenge to computing electron-phonon ($e$-ph) interactions in strongly anharmonic crystals. Here we develop a first-principles approach to compute $e$-ph scattering and charge transport in materials with anharmonic lattice dynamics. Our approach employs renormalized phonons to compute the temperature-dependent $e$-ph coupling for all phonon modes, including the soft modes associated with ferroelectricity and phase transitions. We show that the electron mobility in cubic ${\mathrm{SrTiO}}_3$ is controlled by scattering with longitudinal optical phonons at room temperature and with ferroelectric soft phonons below 200 K. Our calculations can accurately predict the temperature dependence of the electron mobility in ${\mathrm{SrTiO}}_3$ between 150–300 K, and reveal the microscopic origin of its roughly $T^{-3}$ trend. Our approach enables first-principles calculations of $e$-ph interactions and charge transport in broad classes of crystals with phase transitions and strongly anharmonic phonons.

We study Josephson junctions based on inversion-asymmetric but time-reversal symmetric Weyl semimetals under the influence of Zeeman fields. We find that, due to distinct spin textures, the Weyl nodes of opposite chirality respond differently to an external magnetic field. Remarkably, a Zeeman field perpendicular to the junction direction results in a phase shift of opposite sign in the current-phase relations of opposite chirality. This leads to a finite chirality Josephson current (CJC) even in the absence of a phase difference across the junction. This feature could allow for applications in chiralitytronics. In the long junction and zero temperature limit, the CJC embodies a novel quantum anomaly of Goldstone bosons at $\pi$ phase difference which is associated with a ${\mathbb{Z}}_2$ symmetry at low energies. It can be detected experimentally via an anomalous Fraunhofer pattern.

We report plasmon-assisted resonant electron tunneling from a Ag or Au tip to field emission resonances (FERs) of a Ag(111) surface induced by cw laser excitation of a scanning tunneling microscope (STM) junction at visible wavelengths. As a hallmark of the plasmon-assisted resonant tunneling, we observe a downshift of the first peak in the FER spectra by a fixed amount equal to the incident photon energy. STM-induced luminescence measurement for the Ag and Au tip reveals the clear correlation between the laser-induced change in the FER spectra and the plasmonic properties of the junction. Our results clarify a novel resonant electron transfer mechanism in a plasmonic nanocavity.

Using video microscopy and particle-tracking techniques developed for dense Brownian systems of polygons, we study the structure-dynamics relationship in a near-equilibrium 2D glass consisting of anisotropic Penrose kite-shaped colloids. Detailed vibrational properties of kite glasses, both translational and rotational, are obtained using covariance matrix techniques. Different from other colloidal glasses of spheres and ellipsoids, the vibrational modes of kite glasses at low frequencies show a strong translational character with spatially localized rotational modes and extended translational modes. Low-frequency quasilocalized soft modes commonly found in sphere glasses are absent in the translational phonon modes of kite glasses. Soft modes are observed predominantly in the rotational vibrations and correlate well with the spatial distribution of Debye-Waller factors. The local structural entropy field shows a strong correlation with the observed dynamic heterogeneity.

We demonstrate a light-induced formation of coherence in a cold atomic gas system that utilizes the suppression of a competing density wave (DW) order. The condensed atoms are placed in an optical cavity and pumped by an external optical standing wave, which induces a long-range interaction mediated by photon scattering and a resulting DW order above a critical pump strength. We show that the light-induced temporal modulation of the pump wave can suppress this DW order and restore coherence. This establishes a foundational principle of dynamical control of competing orders analogous to a hypothesized mechanism for light-induced superconductivity in high-$T_c$ cuprates.

Quantum computers must be able to function in the presence of decoherence. The simplest strategy for decoherence reduction is dynamical decoupling (DD), which requires no encoding overhead and works by converting quantum gates into decoupling pulses. Here, using the IBM and Rigetti platforms, we demonstrate that the DD method is suitable for implementation in today’s relatively noisy and small-scale cloud-based quantum computers. Using DD, we achieve substantial fidelity gains relative to unprotected, free evolution of individual superconducting transmon qubits. To a lesser degree, DD is also capable of protecting entangled two-qubit states. We show that dephasing and spontaneous emission errors are dominant in these systems, and that different DD sequences are capable of mitigating both effects. Unlike previous work demonstrating the use of quantum error correcting codes on the same platforms, we make no use of postselection and hence report unconditional fidelity improvements against natural decoherence.

The first evidence of events consistent with the production of a single top quark in association with a photon is reported. The analysis is based on proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$ and recorded by the CMS experiment in 2016, corresponding to an integrated luminosity of $35.9{\mathrm{fb}}^{-1}$. Events are selected by requiring the presence of a muon ($\mu$), a photon ($\gamma$), an imbalance in transverse momentum from an undetected neutrino ($\nu$), and at least two jets ($j$) of which exactly one is identified as associated with the hadronization of a $b$ quark. A multivariate discriminant based on topological and kinematic event properties is employed to separate signal from background processes. An excess above the background-only hypothesis is observed, with a significance of 4.4 standard deviations. A fiducial cross section is measured for isolated photons with transverse momentum greater than 25 GeV in the central region of the detector. The measured product of the cross section and branching fraction is $\sigma (pp\to t\gamma \mathrm{j})\mathcal{B}(t\to \mu \nu b)=115\pm 17(\text{stat})\pm 30(\text{syst})\mathrm{fb}$, which is consistent with the standard model prediction.

The cross section for prompt antiproton production in collisions of protons with an energy of 6.5 TeV incident on helium nuclei at rest is measured with the LHCb experiment from a data set corresponding to an integrated luminosity of $0.5{\mathrm{nb}}^{-1}$. The target is provided by injecting helium gas into the LHC beam line at the LHCb interaction point. The reported results, covering antiproton momenta between 12 and $110\mathrm{GeV}/c$, represent the first direct determination of the antiproton production cross section in $p\text{−}\mathrm{He}$ collisions, and impact the interpretation of recent results on antiproton cosmic rays from space-borne experiments.