We introduce a scheme to coherently suppress second-rank tensor frequency shifts in atomic clocks, relying on the continuous rotation of an external magnetic field during the free atomic state evolution in a Ramsey sequence. The method retrieves the unperturbed frequency within a single interrogation cycle and is readily applicable to various atomic clock systems. For the frequency shift due to the electric quadrupole interaction, we experimentally demonstrate suppression by more than two orders of magnitude for the ${{}^{2}S}_{1/2}\to {{}^{2}D}_{3/2}$ transition of a single trapped ${}^{171}{\mathrm{Yb}}^{+}$ ion. The scheme provides particular advantages in the case of the ${}^{171}{\mathrm{Yb}}^{+}$ ${{}^{2}S}_{1/2}\to {{}^{2}F}_{7/2}$ electric octupole (E3) transition. For an improved estimate of the residual quadrupole shift for this transition, we measure the excited state electric quadrupole moments $\mathrm{\Theta }({{}^{2}D}_{3/2})=1.95(1)e{a}_0^2$ and $\mathrm{\Theta }({{}^{2}F}_{7/2})=-0.0297(5)e{a}_0^2$ with $e$ the elementary charge and $a_0$ the Bohr radius, improving the measurement uncertainties by one order of magnitude.

We show that a single photon propagating through a Rydberg-dressed atomic ensemble can exchange its spin state with a single atom. Such a spin-exchange collision exhibits both dissipative and coherent features, depending on the interaction strength. For strong interaction, the collision dissipatively drives the system into an entangled dark state of the photon with an atom. In the weak interaction regime, the scattering coherently flips the spin of a single photon in the multiphoton input pulse, demonstrating a generic single-photon subtracting process. An analytical treatment of this process reveals a universal trade-off between efficiency and purity of the extracted photon, which applies to a wide class of single-photon subtractors. We show that such a trade-off can be optimized by adjusting the scattering rate under a novel phase-matching condition.

Interaction of particles with boundaries is a fundamental problem in many fields of physics. In this Letter, we theoretically examine the fluid-mediated interaction between a horizontally oscillating plate and a spherical particle, revealing emergence of the novel nonlinear vertical force exerted on the particle. Although we demonstrate that the phenomenon only slightly alters deposition of colloidal (sub-)$\mu \mathrm{m}$-sized particles measured by quartz crystal microbalance, it can result in levitation of larger particles above the plate, considerably hindering their deposition.

In experiments performed with the OMEGA EP laser system, magnetic field generation in double ablation fronts was observed. Proton radiography measured the strength, spatial profile, and temporal dynamics of self-generated magnetic fields as the target material was varied between plastic, aluminum, copper, and gold. Two distinct regions of magnetic field are generated in mid-$Z$ targets—one produced by gradients from electron thermal transport and the second from radiation-driven gradients. Extended magnetohydrodynamic simulations including radiation transport reproduced key aspects of the experiment, including field generation and double ablation front formation.

Pressure- and temperature-dependent Raman scattering in GeSe, SnSe, and GeTe for pressures beyond 50 GPa and for temperatures ranging from 78 to 800 K allow us to identify structural and electronic phase transitions, similarities between GeSe and SnSe, and differences with GeTe. Calculations help to deduce the propensity of GeTe for defect formation and the doping that results from it, which gives rise to strong Raman damping beyond anomalous anharmonicity. These properties are related to the underlying chemical bonding and consistent with a recent classification of bonding in several chalcogenide materials that puts GeTe in a separate class of “incipient” metals.

Many processes in chemistry, physics, and biology involve rare events in which the system escapes from a metastable state by surmounting an activation barrier. Examples range from chemical reactions, protein folding, and nucleation events to the catastrophic failure of bridges. A challenge in understanding the underlying mechanisms is that the most interesting information is contained within the rare transition paths, the exceedingly short periods when the barrier is crossed. To establish a model process that enables access to all relevant timescales, although highly disparate, we probe the dynamics of single dielectric particles in a bistable optical trap in solution. Precise localization by high-speed tracking enables us to resolve the transition paths and relate them to the detailed properties of the 3D potential within which the particle diffuses. By varying the barrier height and shape, the experiments provide a stringent benchmark of current theories of transition path dynamics.

The adsorption of gas molecules at the substrate beneath interfacial nanobubbles modifies the energy of the solid-gas interface, and therefore affects their morphology. In this work, we describe a simple thermodynamic model that captures the influence of gas adsorption and gives flat bubble shapes with reduced gas-side contact angles relative to the zero-adsorption case, in agreement with experimental studies. We show that this effect is general to both hydrophilic and hydrophobic substrates and has a stabilizing influence that extends nanobubble lifetimes.

Higher-order topology yields intriguing multidimensional topological phenomena, while Weyl semimetals have unconventional properties such as chiral anomaly. However, so far, Weyl physics remain disconnected with higher-order topology. Here, we report the theoretical discovery of higher-order Weyl semimetals and thereby the establishment of such an important connection. We demonstrate that higher-order Weyl semimetals can emerge in chiral materials such as chiral tetragonal crystals as the intermediate phase between the conventional Weyl semimetal and 3D higher-order topological phases. Higher-order Weyl semimetals manifest themselves uniquely by exhibiting concurrent chiral Fermi-arc surface states, topological hinge states, and the momentum-dependent fractional hinge charge, revealing a novel class of higher-order topological phases.

Graphene nanoribbons (GNRs), low-dimensional platforms for carbon-based electronics, show the promising perspective to also incorporate spin polarization in their conjugated electron system. However, magnetism in GNRs is generally associated with localized states around zigzag edges, difficult to fabricate and with high reactivity. Here we demonstrate that magnetism can also be induced away from physical GNR zigzag edges through atomically precise engineering topological defects in its interior. A pair of substitutional boron atoms inserted in the carbon backbone breaks the conjugation of their topological bands and builds two spin-polarized boundary states around them. The spin state was detected in electrical transport measurements through boron-substituted GNRs suspended between the tip and the sample of a scanning tunneling microscope. First-principle simulations find that boron pairs induce a spin 1, which is modified by tuning the spacing between pairs. Our results demonstrate a route to embed spin chains in GNRs, turning them into basic elements of spintronic devices.

Coherent superposition and entanglement are two fundamental aspects of nonclassicality. Here we provide a quantitative connection between the two on the level of operations by showing that the dynamical coherence of an operation upper bounds the dynamical entanglement that can be generated from it with the help of additional incoherent operations. In case a particular choice of monotones based on the relative entropy is used for the quantification of these dynamical resources, this bound can be achieved. In addition, we show that an analog to the entanglement potential exists on the level of operations and serves as a valid quantifier for dynamical coherence.

The Jaynes-Cummings model is a cornerstone of light-matter interactions. While finite, the model provides an illustrative example of renormalization in perturbation theory. We show, however, that exact renormalization reveals a rich nonperturbative structure, and that the model provides a physical example of a theory with a chaotic coupling trajectory and multivalued $\beta$ function. We also construct an exact Wilsonian-like renormalization group flow for the effective scattering matrix, and show how multivalued features arise in the flow. Our results shed light on nonperturbative aspects of renormalization and on the structure of the Jaynes-Cummings model itself.

We present a new mechanism for thermally produced dark matter, based on a semi-annihilation-like process, $\chi +\chi +\mathrm{SM}\to \chi +\mathrm{SM}$, with intriguing consequences for the properties of dark matter. First, its mass is low, $\lesssim 1\mathrm{GeV}$ (but $\gtrsim 5\mathrm{keV}$ to avoid structure-formation constraints). Second, it is strongly interacting, leading to kinetic equilibrium between the dark and visible sectors, avoiding the structure-formation problems of $\chi +\chi +\chi \to \chi +\chi$ models. Third, in the $3\to 2$ process, one dark matter particle is consumed, giving the standard-model particle a monoenergetic recoil. We show that this new scenario is presently allowed, which is surprising (perhaps a “minor miracle”). However, it can be systematically tested by novel analyses in present and near-term experiments. In particular, the Co-SIMP model for thermal-relic dark matter can explain the XENON1T excess.

We present a constructive derivation of all four-point tree-level holographic correlators for eleven dimensional supergravity on ${\mathrm{AdS}}_7\times S^4$. These correlators correspond to four-point functions of arbitrary one-half BPS operators in the six-dimensional (2,0) theory at large central charge. The crucial observation is that the polar part of the correlators in Mellin space is fully captured by a drastically simpler maximally $R$-symmetry violating amplitude, while the contact part is fully fixed by superconformal Ward identities and the flat space limit.

We report the first observation of two wobbling bands in ${}^{183}\mathrm{Au}$, both of which were interpreted as the transverse wobbling (TW) band but with different behavior of their wobbling energies as a function of spin. It increases (decreases) with spin for the positive (negative) parity configuration. The crucial evidence for the wobbling nature of the bands, dominance of the $E2$ component in the $\mathrm{\Delta }I=1$ transitions between the partner bands, is provided by the simultaneous measurements of directional correlation from the oriented states ratio and the linear polarization of the $\gamma$ rays. Particle rotor model calculations with triaxial deformation reproduce the experimental data well. A value of spin, $I_m$, has been determined for the observed TW bands below which the wobbling energy increases and above which it decreases with spin. The nucleus ${}^{183}\mathrm{Au}$ is, so far, the only nucleus in which both the increasing and the decreasing parts are observed and thus gives the experimental evidence of the complete transverse wobbling phenomenon.

We study a two-dimensional low-dissipation nonautonomous dynamical system, with a control parameter that is swept linearly in time across a transcritical bifurcation. We investigate the relaxation time of a perturbation applied to a variable of the system and we show that critical slowing down may occur at a parameter value well above the bifurcation point. We test experimentally the occurrence of critical slowing down by applying a perturbation to the accessible control parameter and we find that this perturbation leaves the system behavior unaltered, thus providing no useful information on the occurrence of critical slowing down. The theoretical analysis reveals the reasons why these tests fail in predicting an incoming bifurcation.

In the three-dimensional (3D) Heisenberg model, topological point defects known as spin hedgehogs behave as emergent magnetic monopoles, i.e., quantized sources and sinks of gauge fields that couple strongly to conduction electrons, and cause unconventional transport responses such as the gigantic Hall effect. We observe a dramatic change in the Hall effect upon the transformation of a spin hedgehog crystal in a chiral magnet MnGe through combined measurements of magnetotransport and small-angle neutron scattering (SANS). At low temperatures, well-defined SANS peaks and a negative Hall signal are each consistent with expectations for a static hedgehog lattice. In contrast, a positive Hall signal takes over when the hedgehog lattice fluctuates at higher temperatures, with a diffuse SANS signal observed upon decomposition of the hedgehog lattice. Our approach provides a simple way to both distinguish and disentangle the roles of static and dynamic emergent monopoles on the augmented Hall motion of conduction electrons.