The hair bundle of sensory cells in the vertebrate ear provides an example of a noisy oscillator close to a Hopf bifurcation. The analysis of the data from both spontaneous and forced oscillations shows a strong violation of the fluctuation-dissipation theorem, revealing the presence of an underlying active process that keeps the system out of equilibrium. Nevertheless, we show that a generalized fluctuation-dissipation theorem, valid for nonequilibrium steady states, is fulfilled within the limits of our experimental accuracy and computational approximations, when the adequate conjugate degrees of freedom are chosen.

The ${}^{229}\mathrm{Th}$ nucleus possesses the lowest-energy nuclear isomeric state. Two widely accepted indirect measurements of the transition energy place it within reach of existing laser capabilities. Direct searches for the isomer deexcitation have proven elusive despite extensive effort over the past couple of decades. There is now a growing interest in finding this unique transition because of its potential applications in nuclear, atomic, condensed matter, and optical physics, quantum information, metrology, and cosmology, including the development of a new type of clock based on this nuclear transition. In this Letter we report the first direct observation of the deexcitation of the lowest-lying isomeric state in ${}^{229}\mathrm{Th}$. By collecting ${}^{229}\mathrm{Th}$ recoils following the alpha decay of ${}^{233}\mathrm{U}$ into ${\mathrm{MgF}}_2$ plates and measuring the subsequent light emission, we have isolated the isomer deexcitation and measured the transition’s half-life to be $6\pm 1\mathrm{h}$. Through comparison measurements with ${}^{235\mathrm{m}}\mathrm{U}$ isomer, we found that the observed ${}^{229\mathrm{m}}\mathrm{Th}$ deexcitation signal originates from photon emission rather than internal conversion electron emission. This discovery lays the groundwork for optical and laser spectroscopy of ${}^{229\mathrm{m}}\mathrm{Th}$ nuclear isomer and the development of a ${}^{229}\mathrm{Th}$ nuclear clock.

It has been argued that requiring low electroweak fine-tuning (EWFT) along with a (partial) decoupling solution to the supersymmetry (SUSY) flavor and $CP$ problems leads to a sparticle mass spectra characterized by light Higgsinos at 100–300 GeV, sub-TeV third generation scalars, gluinos at a few TeV, and multi-TeV first or second generation scalars (natural SUSY). We show that by starting with multi-TeV first or second and third generation scalars and trilinear soft breaking terms, the natural SUSY spectrum can be generated radiatively via renormalization group running effects. Using the complete 1-loop effective potential to calculate EWFT, significantly heavier third generation squarks can be allowed even with low EWFT. The large negative trilinear term and heavier top squarks allow for a light Higgs scalar in the $\sim 125\mathrm{GeV}$ regime.

The orbital $M1$ scissors resonance has been measured for the first time in the quasicontinuum of actinides. Particle-$\gamma$ coincidences are recorded with deuteron and ${}^3\mathrm{He}$-induced reactions on ${}^{232}\mathrm{Th}$. The residual nuclei ${}^{231,232,233}\mathrm{Th}$ and ${}^{232,233}\mathrm{Pa}$ show an unexpectedly strong integrated strength of $B_{M1}=11–15{\mu }_n^2$ in the $E_{\gamma }=1.0–3.5\mathrm{MeV}$ region. The increased $\gamma$-decay probability in actinides due to scissors resonance is important for cross-section calculations for future fuel cycles of fast nuclear reactors and may also have an impact on stellar nucleosynthesis.

We study vibrational excitations, dissociation, and ionization of ${\mathrm{H}}_2^{+}$ in few-cycle laser pulses over a broad wavelength regime. Our results of numerical simulations supported by model calculations show a many orders-of-magnitude enhancement of vibrational excitation and dissociation (over ionization) of the molecular ion at infrared wavelengths. The enhancement occurs without any chirping of the pulse, which was previously applied to take account of the anharmonicity of the molecular vibrations. The effect is related to strong-field two- and higher-order photon transitions between different vibrational states.

We present a study of multiphoton dissociative ionization from molecules. By solving the time-dependent Schrödinger equation for ${\mathrm{H}}_2^{+}$ and projecting the solution onto double continuum scattering states, we observe the correlated electron-nuclear ionization dynamics in detail. We show—for the first time—how multiphoton structure prevails as long as one accounts for the energies of all the fragments. Our current work provides a new avenue to analyze strong-field fragmentation that leads to a deeper understanding of the correlated molecular dynamics.

We measure the dynamics of a nonclassical optical field using two-time second-order correlations in conjunction with pulsed excitation. The technique quantifies single-photon purity and coherence during the excitation-decay cycle of an emitter, illustrated here using a quantum dot. We observe that for certain pump wavelengths, photons detected early in the cycle have reduced single-photon purity and coherence compared to those detected later. A model indicates that the single-photon purity dynamics are due to exciton recapture after initial emission and within the same pulse cycle.

We show that a model based on anticrossing between highly group velocity-mismatched gap-guided and index-guided modes describes gap soliton propagation in photonic crystal waveguides. Such nonlinear solutions can be exploited for exploring new regimes such as all-optical control of group velocity (dispersionless slow light) over a submillimeter length scale, and propagation beyond the linear modal cutoff. The results are validated by means of finite-difference time domain simulations.

We experimentally demonstrate a class of tractor beams created by coherently superposing coaxial Bessel beams. These optical conveyors have periodic intensity variations along their axes that act as highly effective optical traps for micrometer-scale objects. Trapped objects can be moved selectively upstream or downstream along the conveyor by appropriately changing the Bessel beams’ relative phase. The same methods used to project a single optical conveyor can project arrays of independent optical conveyors, allowing bidirectional transport in three dimensions.

We analyze record-breaking events in time series of continuous random variables that are subsequently discretized by rounding to integer multiples of a discretization scale $\Delta >0$. Rounding leads to ties of an existing record, thereby reducing the number of new records. For an infinite number of random variables that are drawn from distributions with a finite upper limit, the number of discrete records is finite, while for distributions with a thinner than exponential upper tail, fewer discrete records arise compared to continuous variables. In the latter case, the record sequence becomes highly regular at long times.

We describe the first direct observation of the significant suppression of the energy spread induced by coherent synchrotron radiation by a pair of conductive plates placed inside a dipole magnet. In addition to various feedback loops improving the energy stability of the beam parameters, our key innovation for this experiment is the observation of the time-resolved energy variation within the electron bunch, instead of the traditionally measured rms energy spread. We present the results of the experiments and compare them with a rigorous analytical theory.

The effect of guide field on magnetic reconnection is quantitatively studied by systematically varying an applied guide field in the Magnetic Reconnection Experiment (MRX). The quadrupole field, a signature of two-fluid reconnection at zero guide field, is altered by a finite guide field. It is shown that the reconnection rate is significantly reduced with increasing guide field, and this dependence is explained by a combination of local and global physics: locally, the in-plane Hall currents are reduced, while globally guide field compression produces an increased pressure both within and downstream of the reconnection region.

Experimentally measured velocities are used to obtain the one- and two-particle distribution functions $f_1$ and $f_2$ and the two-particle correlation function $g_2\equiv f_2-f_1{f}_1$. The fluctuating velocities of interacting charged microparticles were recorded by tracking their motion while they were immersed in a dusty plasma. The phase space was reduced by having only two particles in a harmonic one dimensional confining potential. In statistical theory, $g_2$ is usually said to be dominated by the randomness of collisions, but here we find that it is dominated by collective oscillatory modes.

Pure glass is defined as a thermodynamic phase in which typical equilibrium particle configurations have macroscopic overlaps with one of some special irregular configurations. By employing 128 types of artificial molecules, a pure glass model is constructed in the cubic lattice.

We establish that the interplay of itinerant fermions with localized magnetic moments on a checkerboard lattice leads to magnetic flux phases. For weak itineracy the flux phase is coplanar and the electronic dispersion takes the shape of graphenelike Dirac fermions. Stronger itineracy drives the formation of a noncoplanar, chiral flux phase, in which the Dirac fermions acquire a topological mass that is proportional to a ferromagnetic spin polarization. Consequently the system self-organizes into a ferromagnetic quantum anomalous Hall state in which the direction of its dissipationless edge currents can be switched by an applied magnetic field.

Using optical, TEM, and ultrafast electron diffraction experiments we find that single crystal ${\mathrm{VO}}_2$ microbeams gently placed on insulating substrates or metal grids exhibit different behaviors, with structural and metal-insulator transitions occurring at the same temperature for insulating substrates, while for metal substrates a new monoclinic metal phase lies between the insulating monoclinic phase and the metallic rutile phase. The structural and electronic phase transitions in these experiments are strongly first order and we discuss their origins in the context of current understanding of multiorbital splitting, strong correlation effects, and structural distortions that act cooperatively in this system.

Using scanning tunneling spectroscopy, we study a 3D topological insulator ${\mathrm{Bi}}_2{\mathrm{Te}}_3$ with a periodic structural deformation (buckling). The buckled surface allows us to measure the response of Dirac electrons in a magnetic field to the presence of a well-defined potential variation. We find that while the $n=0$ Landau level exhibits a 12 meV energy shift across the buckled structure at 7 T, the amplitude of this shift changes with the Landau level index. Modeling these effects reveals that the Landau level behavior encodes information on the spatial extent of their wave functions. Our findings have important implications for transport and magnetoresistance measurements in Dirac materials with engineered potential landscapes.

Strain-induced gradients of local electric fields in semiconductor quantum dots can couple to the quadrupole moments of nuclear spins. We develop a theory describing the influence of this quadrupolar coupling on the spin correlators of electron and hole “central” spins localized in such dots. We show that when the quadrupolar coupling strength is comparable to or larger than the hyperfine coupling strength between nuclei and the central spin, the relaxation rate of the central spin is strongly enhanced and can be exponential. We demonstrate a good agreement with recent experiments on spin relaxation in hole-doped (In,Ga)As self-assembled quantum dots.

We theoretically study field-induced domain wall motion in an electrically insulating ferromagnet with hard- and easy-axis anisotropies. Domain walls can propagate along a dissipationless wire through spin wave emission locked into the known soliton velocity at low fields. In the presence of damping, the usual Walker rigid-body propagation mode can become unstable for a magnetic field smaller than the Walker breakdown field.

The dynamics of the photoinduced commensurate-to-incommensurate charge density wave (CDW) phase transition in $4H_b\mathrm{\text{−}}{\mathrm{TaSe}}_2$ are investigated by femtosecond electron diffraction. In the perturbative regime, the CDW re-forms on a 150-ps time scale, which is two orders of magnitude slower than in other transition-metal dichalcogenides. We attribute this to a weak coupling between the CDW carrying $T$ layers and thus demonstrate the importance of three-dimensionality for the existence of CDWs. With increasing optical excitation, the phase transition is achieved, showing a second-order character, in contrast to the first-order behavior in thermal equilibrium.