We study the quantum phase transition of interacting electrons in quantum wires from a one-dimensional (1D) linear configuration to a quasi-1D zigzag arrangement using quantum Monte Carlo methods. As the density increases from its lowest values, first, the electrons form a linear Wigner crystal, then, the symmetry about the axis of the wire is broken as the electrons order in a quasi-1D zigzag phase, and, finally, the electrons form a disordered liquidlike phase. We show that the linear to zigzag phase transition is not destroyed by the strong quantum fluctuations present in narrow wires; it has characteristics which are qualitatively different from the classical transition.

We perform measurements of phase-slip-induced switching current events on different types of superconducting weak links and systematically study statistical properties of the switching current distributions. We employ two types of devices in which a weak link is formed either by a superconducting nanowire or by a graphene flake subject to proximity effect. We demonstrate that independently of the nature of the weak link, higher moments of the distribution take universal values. In particular, the third moment (skewness) of the distribution is close to $-1$ both in thermal and quantum regimes. The fourth moment (kurtosis) also takes a universal value close to 5. The discovered universality of skewness and kurtosis is confirmed by an analytical model. Our numerical analysis shows that introduction of extraneous noise into the system leads to significant deviations from the universal values. We suggest using the discovered universality of higher moments as a robust tool for checking against undesirable effects on noise in various types of measurements.

We report the effective methods to induce weak ferromagnetism in pristine ${\mathrm{MoS}}_2$ persisting up to room temperature with the improved transport property, which would lead to new spintronics devices. The hydrogenation of ${\mathrm{MoS}}_2$ by heating at $300°\mathrm{C}$ for 1 h leads to the easy axis out of plane, while the irradiation of proton with a dose of $1\times {10}^{13}\mathrm{P}/{\mathrm{cm}}^2$ leads to the easy axis in plane. The theoretical modeling supports such magnetic easy axes.

The temperature ($T$) dependence of the optical conductivity spectra $\sigma (\omega )$ of a single crystal ${\mathrm{SrRuO}}_3$ thin film is studied over a $T$ range from 5 to 450 K. We observed significant $T$ dependence of the spectral weights of the charge transfer and interband $d\mathrm{\text{−}}d$ transitions across the ferromagnetic Curie temperature ($T_c\sim 150\mathrm{K}$). Such $T$ dependence was attributed to the increase in the Ru spin moment, which is consistent with the results of density functional theory calculations. $T$ scans of $\sigma (\Omega ,T)$ at fixed frequencies $\Omega$ reveal a clear $T^2$ dependence below $T_c$, demonstrating that the Stoner mechanism is involved in the evolution of the electronic structure. In addition, $\sigma (\Omega ,T)$ continues to evolve at temperatures above $T_c$, indicating that the local spin moment persists in the paramagnetic state. This suggests that ${\mathrm{SrRuO}}_3$ is an intriguing oxide system with itinerant ferromagnetism.

I compute exact partition function zeros of the Wako-Saitô-Muñoz-Eaton model for various secondary structural elements and for two proteins, 1BBL and 1I6C, by using both analytic and numerical methods. Two-state and barrierless downhill folding transitions can be distinguished by a gap in the distribution of zeros at the positive real axis.

Cooperativity arising from local interactions in equilibrium receptor systems provides gain, but does not increase sensory performance, as measured by the signal-to-noise ratio (SNR) due to a fundamental tradeoff between gain and intrinsic noise. Here we allow sensing to be a nonequilibrium process and show that energy dissipation cannot circumvent the fundamental tradeoff, so that the SNR is still optimal for independent receptors. For systems requiring high gain, nonequilibrium 2D-coupled receptors maximize the SNR, revealing a new design principle for biological sensors.

The passive mechanical response of skeletal muscles at fast time scales is dominated by long range interactions inducing cooperative behavior without breaking the detailed balance. This leads to such unusual “material properties” as negative equilibrium stiffness and different behavior in force and displacement controlled loading conditions. Our fitting of experimental data suggests that “muscle material” is finely tuned to perform close to a critical point which explains large fluctuations observed in muscles close to the stall force.

We investigate the change of the static friction threshold of weakly adhesive amorphous interfaces in the presence of the shear ultrasonic oscillation. Prior to sliding, a softening of the shear interfacial stiffness is observed under either static or high-amplitude oscillatory shear. We find that the nonlinear shear ultrasound, regardless of its polarization, triggers the macroscopic sliding at these interfaces far below the static threshold. Such unjamming transition is due to the vibration-induced decrease of the apparent coefficient of static friction, which provides a mechanism for understanding the reduction of the yielding threshold of granular media by the acoustic fluidization.

It is suggested that Goldstone bosons may be masquerading as fractional cosmic neutrinos, contributing about 0.39 to what is reported as the effective number of neutrino types in the era before recombination. The broken symmetry associated with these Goldstone bosons is further speculated to be the conservation of the particles of dark matter.

We formulate the in-medium similarity renormalization group (IM-SRG) for open-shell nuclei using a multireference formalism based on a generalized Wick theorem introduced in quantum chemistry. The resulting multireference IM-SRG (MR-IM-SRG) is used to perform the first ab initio study of all even oxygen isotopes with chiral nucleon-nucleon and three-nucleon interactions, from the proton to the neutron drip lines. We obtain an excellent reproduction of experimental ground-state energies with quantified uncertainties, which is validated by results from the importance-truncated no-core shell model and the coupled cluster method. The agreement between conceptually different many-body approaches and experiment highlights the predictive power of current chiral two- and three-nucleon interactions, and establishes the MR-IM-SRG as a promising new tool for ab initio calculations of medium-mass nuclei far from shell closures.

In recent experiments at the velocity filter Separator for Heavy Ion reaction Products (SHIP) (GSI, Darmstadt), an extended and improved set of $\alpha$-decay data for more than 20 of the most neutron-deficient isotopes in the region from lead to thorium was obtained. The combined analysis of this newly available $\alpha$-decay data, of which the ${}^{186}\mathrm{Po}$ decay is reported here, allowed us for the first time to clearly show that crossing the $Z=82$ shell to higher proton numbers strongly accelerates the $\alpha$ decay. From the experimental data, the $\alpha$-particle formation probabilities are deduced following the Universal Decay Law approach. The formation probabilities are discussed in the framework of the pairing force acting among the protons and the neutrons forming the $\alpha$ particle. A striking resemblance between the phenomenological pairing gap deduced from experimental binding energies and the formation probabilities is noted. These findings support the conjecture that both the $N=126$ and $Z=82$ shell closures strongly influence the $\alpha$-formation probability.

We investigate the current noise correlations at a quantum point contact in a quantum spin Hall structure, focusing on the effect of a weak magnetic field in the presence of disorder. For the case of two equally biased terminals we discover a robust peak: the noise correlations vanish at $B=0$ and are negative for $B\ne 0$. We find that the character of this peak is intimately related to the interplay between time reversal symmetry and the helical nature of the edge states and call it the ${\mathbb{Z}}_2$ peak.

We demonstrate an organic molecule with an energy gap between its singlet and triplet excited states of almost zero ($\Delta E_{\mathrm{ST}}\sim 0\mathrm{eV}$). Such separation was realized through proper combination of an electron-donating indolocarbazole group and a diphenyltriazine electron-accepting moiety. Calculated and measured $\Delta E_{\mathrm{ST}}$ were 0.003 and 0.02 eV, respectively. A total photoluminescence efficiency of $59\%\pm 2\%$ with $45\%\pm 2\%$ from a delayed component and $14\%\pm 2\%$ from a prompt component was obtained for a doped film. Organic light emitting diodes containing this molecule as an emitting dopant exhibited an unexpectedly high external electroluminescence efficiency of ${\eta }_{\mathrm{EQE}}=14\%\pm 1\%$.

We propose an experimental scheme to verify the quantum nonequilibrium fluctuation relations using current technology. Specifically, we show that the characteristic function of the work distribution for a nonequilibrium quench of a general quantum system can be extracted by Ramsey interferometry of a single probe qubit. Our scheme paves the way for the full characterization of nonequilibrium processes in a variety of quantum systems, ranging from single particles to many-body atomic systems and spin chains. We demonstrate our idea using a time-dependent quench of the motional state of a trapped ion, where the internal pseudospin provides a convenient probe qubit.

We propose an interferometric setting for the ancilla-assisted measurement of the characteristic function of the work distribution following a time-dependent process experienced by a quantum system. We identify how the configuration of the effective interferometer is linked to the symmetries enjoyed by the Hamiltonian ruling the process and provide the explicit form of the operations to implement in order to accomplish our task. We finally discuss two physical settings, based on hybrid optomechanical-electromechanical devices, where the theoretical proposals discussed in our work could find an experimental demonstration.

We present a stochastic model for amplifying, diffusive media such as, for instance, random lasers. Starting from a simple random-walk model, we derive a stochastic partial differential equation for the energy field which contains a multiplicative random-advection term yielding intermittency and power-law distributions of the field itself. A dimensional analysis indicates that such features are more likely to be observed for small enough samples and in lower spatial dimensions.

We experimentally demonstrate a robust scheme to select a single high-order harmonic among the harmonic comb by using a driving laser field with subcycle waveform control, which is synthesized by the fundamental 800 nm laser pulse and two controlling laser pulses at 400 and 267 nm with perpendicular polarizations. By controlling the relative phase among the pulses of different colors, a single high-order harmonic is selectively enhanced while the adjacent harmonics are greatly suppressed with the intensity contrast increased by more than 1 order of magnitude and the peak intensity enhanced simultaneously by more than 2 orders of magnitude compared to the case by using only the fundamental 800 nm laser pulse. Such phenomena can be mainly attributed to the intra-atomic phase matching realized with the sub-cycle waveform controlled field.

We present a laboratory study on the instability of internal wave attractors in a trapezoidal fluid domain filled with uniformly stratified fluid. Energy is injected into the system via standing-wave-type motion of a vertical wall. Attractors are found to be destroyed by parametric subharmonic instability via a triadic resonance which is shown to provide a very efficient energy pathway from long to short length scales. This Letter provides an explanation of why attractors may be difficult or impossible to observe in natural systems subject to large amplitude forcing.

We investigate the behavior of a two-dimensional inviscid and incompressible flow when pushed out of dynamical equilibrium. We use the two-dimensional vorticity equation with spectral truncation on a rectangular domain. For a sufficiently large number of degrees of freedom, the equilibrium statistics of the flow can be described through a canonical ensemble with two conserved quantities, energy and enstrophy. To perturb the system out of equilibrium, we change the shape of the domain according to a protocol, which changes the kinetic energy but leaves the enstrophy constant. We interpret this as doing work to the system. Evolving along a forward and its corresponding backward process, we find numerical evidence that the distributions of the work performed satisfy the Crooks relation. We confirm our results by proving the Crooks relation for this system rigorously.

In this Letter a hydrodynamic theory of liquid slippage on a solid substrate near a moving contact line is proposed. A family of spatially varying slip lengths in the Navier slip law recovers the results of past formulations for slip in continuum theories and molecular dynamics simulations and is consistent with well-established experimental observations of complete wetting. This formulation gives a general approach for continuum hydrodynamic theories. New fluid flow behaviors are also predicted yet to be seen in experiment.