We present the measurement of ferromagnetic resonance (FMR-)driven spin pumping and three-terminal electrical spin injection within the same silicon-based device. Both effects manifest in a dc spin accumulation voltage $V_s$ that is suppressed as an applied field is rotated to the out-of-plane direction, i.e., the oblique Hanle geometry. Comparison of $V_s$ between these two spin injection mechanisms reveals an anomalously strong suppression of FMR-driven spin pumping with increasing out-of-plane field $H_{\text{app}}^z$. We propose that the presence of the large ac component to the spin current generated by the spin pumping approach, expected to exceed the dc value by 2 orders of magnitude, is the origin of this discrepancy through its influence on the spin dynamics at the oxide-silicon interface. This convolution, wherein the dynamics of both the injector and the interface play a significant role in the spin accumulation, represents a new regime for spin injection that is not well described by existing models of either FMR-driven spin pumping or electrical spin injection.

We expand the well-known notion that quantum criticality can induce superconductivity by proposing a concrete mechanism for superconductivity due to quantum ferroelectric fluctuations. To this end, we investigate the origin of superconductivity in doped ${\mathrm{SrTiO}}_3$ using a combination of density functional and strong coupling theories within the framework of quantum criticality. Our density functional calculations of the ferroelectric soft mode frequency as a function of doping reveal a crossover related to quantum paraelectricity at a doping level coincident with the experimentally observed top of the superconducting dome. Thus, we suggest a model in which the soft mode fluctuations provide the pairing interaction for superconductivity carriers. Within our model, the low doping limit of the superconducting dome is explained by the emergence of the Fermi surface, and the high doping limit by departure from the quantum critical regime. We predict that the highest critical temperature will increase and shift to lower carrier doping with increasing ${}^{18}\mathrm{O}$ isotope substitution, a scenario that is experimentally verifiable. Our model is applicable to other quantum paraelectrics, such as ${\mathrm{KTaO}}_3$.

We consider two species of bosons in one dimension near the Tonks-Girardeau limit of infinite interactions. For the case of equal masses and equal intraspecies interactions, the system can be mapped to a $S=1/2$ $XXZ$ Heisenberg spin chain, thus allowing one to access different magnetic phases. Using a powerful ansatz developed for the two-component Fermi system, we elucidate the evolution from few to many particles for the experimentally relevant case of an external harmonic confinement. In the few-body limit, we already find clear evidence of both ferromagnetic and antiferromagnetic spin correlations as the ratio of intraspecies and interspecies interactions is varied. Furthermore, we observe the rapid emergence of symmetry-broken magnetic ground states as the particle number is increased. We therefore demonstrate that systems containing only a few bosons are an ideal setting in which to realize the highly sought-after itinerant ferromagnetic phase.

We report an entropy-driven orientational hopping transition in a magnetically confined colloidal Janus rod. In a magnetic field, the sedimented rod randomly hops between horizontal and vertical states: the latter state comes at a substantial gravitational cost at no reduction of magnetic potential energy. The probability distribution over the angles of the rod shows that the presence of an external magnetic field leads to the emergence of a metastable vertical state separated from the ground state by an effective barrier. This barrier does not come from the potential energy but rather from the vast gain in phase space available to the rod as it approaches the vertical state. The loss of rotational degree of freedom that gives rise to this effect is a statistical mechanical analogue of the phenomenon of gimbal lock from classical mechanics.

In this paper we follow the analysis and protocols of recent experiments, combined with simple theory, to arrive at a physical understanding of quasi-condensation in two dimensional Fermi gases. A key signature of quasi-condensation, which contains aspects of Berezinskiĭ-Kosterlitz-Thouless behavior, is a strong zero momentum peak in the pair momentum distribution. Importantly, this peak emerges at a reasonably well defined onset temperature. The resulting phase diagram, pair momentum distribution, and algebraic power law decay are compatible with recent experiments throughout the continuum from BEC to BCS.

We engineer a quantum bath that enables entropy and energy exchange with a one-dimensional Bose-Hubbard lattice with attractive on-site interactions. We implement this in an array of three superconducting transmon qubits coupled to a single cavity mode; the transmons represent lattice sites and their excitation quanta embody bosonic particles. Our cooling protocol preserves the particle number—realizing a canonical ensemble—and also affords the efficient preparation of dark states which, due to symmetry, cannot be prepared via coherent drives on the cavity. Furthermore, by applying continuous microwave radiation, we also realize autonomous feedback to indefinitely stabilize particular eigenstates of the array.

We propose a digital quantum simulator of non-Abelian pure-gauge models with a superconducting circuit setup. Within the framework of quantum link models, we build a minimal instance of a pure SU(2) gauge theory, using triangular plaquettes involving geometric frustration. This realization is the least demanding, in terms of quantum simulation resources, of a non-Abelian gauge dynamics. We present two superconducting architectures that can host the quantum simulation, estimating the requirements needed to run possible experiments. The proposal establishes a path to the experimental simulation of non-Abelian physics with solid-state quantum platforms.

Although there are many theoretical studies of the mean first-passage time (MFPT), most neglect the diffusive heterogeneity of real systems. We present exact analytical expressions for the MFPT and residence times of a pointlike particle diffusing in a spherically symmetric $d$-dimensional heterogeneous system composed of two concentric media with different diffusion coefficients with an absorbing inner boundary (target) and a reflecting outer boundary. By varying the convention, e.g., Itō, Stratonovich, or isothermal, chosen to interpret the overdamped Langevin equation with multiplicative noise describing the diffusion process, we find different predictions and counterintuitive results for the residence time in the outer region and hence for the MFPT, while the residence time in the inner region is independent of the convention. This convention dependence of residence times and the MFPT could provide insights about the heterogeneous diffusion in a cell or in a tumor, or for animal and insect searches inside their home range.

We optically excite the electronic state $3s3p$ ${}^3{P}_0$ in ${}^{24}\mathrm{Mg}$ atoms, laser cooled and trapped in a magic-wavelength lattice. An applied magnetic field enhances the coupling of the light to the otherwise strictly forbidden transition. We determine the magic wavelength, the quadratic magnetic Zeeman shift, and the transition frequency to be 468.46(21) nm, $-206.6(2.0)\mathrm{MHz}/{\mathrm{T}}^2$, and 655 058 646 691(101) kHz, respectively. These are compared with theoretical predictions and results from complementary experiments. We also develop a high-precision relativistic structure model for magnesium, give an improved theoretical value for the blackbody radiation shift, and discuss a clock based on bosonic magnesium.

Without Lorentz invariance, spontaneous global symmetry breaking can lead to multicritical Nambu-Goldstone modes with a higher-order low-energy dispersion $\omega \sim k^n$ ($n=2,3,\dots$), whose naturalness is protected by polynomial shift symmetries. Here, we investigate the role of infrared divergences and the nonrelativistic generalization of the Coleman-Hohenberg-Mermin-Wagner (CHMW) theorem. We find novel cascading phenomena with large hierarchies between the scales at which the value of $n$ changes, leading to an evasion of the “no-go” consequences of the relativistic CHMW theorem.

It has been predicted and experimentally demonstrated that by injecting squeezed light into an optomechanical device, it is possible to enhance the precision of a position measurement. Here, we present a fundamentally different approach where the squeezing is created directly inside the cavity by a nonlinear medium. Counterintuitively, the enhancement of the signal-to-noise ratio works by deamplifying precisely the quadrature that is sensitive to the mechanical motion without losing quantum information. This enhancement works for systems with a weak optomechanical coupling and/or strong mechanical damping. This can allow for larger mechanical bandwidth of quantum-limited detectors based on optomechanical devices. Our approach can be straightforwardly extended to quantum nondemolition qubit detection.

We investigate the dynamics of the Higgs field at the end of inflation in the minimal scenario consisting of an inflaton field coupled to the standard model only through the nonminimal gravitational coupling $\xi$ of the Higgs field. Such a coupling is required by renormalization of the standard model in curved space, and in the current scenario also by vacuum stability during high-scale inflation. We find that for $\xi \gtrsim 1$, rapidly changing spacetime curvature at the end of inflation leads to significant production of Higgs particles, potentially triggering a transition to a negative-energy Planck scale vacuum state and causing an immediate collapse of the Universe.

We present the first ab initio calculation of a radiative transition of a hadronic resonance within quantum chromodynamics (QCD). We compute the amplitude for $\pi \pi \to \pi {\gamma }^{\star }$, as a function of the energy of the $\pi \pi$ pair and the virtuality of the photon, in the kinematic regime where $\pi \pi$ couples strongly to the unstable $\rho$ resonance. This exploratory calculation is performed using a lattice discretization of QCD with quark masses corresponding to $m_{\pi }\approx 400\mathrm{MeV}$. We obtain a description of the energy dependence of the transition amplitude, constrained at 48 kinematic points, that we can analytically continue to the $\rho$ pole and identify from its residue the $\rho \to \pi {\gamma }^{\star }$ form factor.

We report the observation of transverse polarization-dependent azimuthal correlations in charged pion pair production with the STAR experiment in $p^{\uparrow }+p$ collisions at RHIC. These correlations directly probe quark transversity distributions. We measure signals in excess of 5 standard deviations at high transverse momenta, at high pseudorapidities $\eta >0.5$, and for pair masses around the mass of the $\rho$ meson. This is the first direct transversity measurement in $p+p$ collisions.

Recent work has shown that collective single photon emission from an ensemble of resonate two-level atoms, i.e., single photon superradiance, is a rich field of study. The present Letter addresses the flip side of superradiance, i.e., subradiance. Single photon subradiant states are potentially stable against collective spontaneous emission and can have ultrafast readout. In particular it is shown how many atom collective effects provide a new way to control spontaneous emission by preparing and switching between subradiant and superradiant states.

We report an extended family of spin textures of zero-dimensional exciton-polaritons spatially confined in tunable open microcavity structures. The transverse-electric–transverse-magnetic (TE-TM) splitting, which is enhanced in the open cavity structures, leads to polariton eigenstates carrying quantized spin vortices. Depending on the strength and anisotropy of the cavity confining potential and of the TE-TM induced splitting, which can be tuned via the excitonic or photonic fractions, the exciton-polariton emissions exhibit either spin-vortex-like patterns or linear polarization, in good agreement with theoretical modeling.

We performed high-pressure study for a Mott insulator ${\mathrm{BaFe}}_2{\mathrm{S}}_3$, by measuring dc resistivity and ac susceptibility up to 15 GPa. We found that the antiferromagnetic insulating state at the ambient pressure is transformed into a metallic state at the critical pressure, $P_c=10\mathrm{GPa}$, and the superconductivity with the optimum $T_c=24\mathrm{K}$ emerges above $P_c$. Furthermore, we found that the metal-insulator transition (Mott transition) boundary terminates at a critical point around 10 GPa and 75 K. The obtained pressure-temperature ($P\text{−}T$) phase diagram is similar to those of the organic and fullerene compounds; namely, ${\mathrm{BaFe}}_2{\mathrm{S}}_3$ is the first inorganic superconductor in the vicinity of bandwidth control type Mott transition.

A phase from an adiabatic exchange of Majorana bound states (MBS) reveals their exotic anyonic nature. For detecting this exchange phase, we propose an experimental setup consisting of a Corbino geometry Josephson junction on the surface of a topological insulator, in which two MBS at zero energy can be created and rotated. We find that if a metallic tip is weakly coupled to a point on the junction, the time-averaged differential conductance of the tip-Majorana coupling shows peaks at the tip voltages $eV=\pm (\alpha -2\pi l)\hslash /T_J$, where $\alpha =\pi /2$ is the exchange phase of the two circulating MBS, $T_J$ is the half rotation time of MBS, and $l$ an integer. This result constitutes a clear experimental signature of Majorana fermion exchange.