Hall anomaly related to deviations in Hall carrier concentrations have always been recognized as signs of charge incoherence in organic semiconductors, which lack ordered lattices. In this paper, we show that the Hall carrier concentration anomaly in doped polymers might be a result of semimetallization. Based on the observation of semimetal-like states, a dual-channel model, in which electrons and holes compensate the Hall voltages of each other, is employed to account for the anomaly. Observations of possible nonlinear Hall effect and temperature dependent Hall signs further support the origin of Hall anomaly from semimetal states.

Stochasticity plays a central role in nearly every biological process, and the noise power spectral density (PSD) is a critical tool for understanding variability and information processing in living systems. In steady state, many such processes can be described by stochastic linear time-invariant (LTI) systems driven by Gaussian white noise, whose PSD is a complex rational function of the frequency that can be concisely expressed in terms of their Jacobian, dispersion, and diffusion matrices, fully defining the statistical properties of the system's dynamics at steady state. Here, we arrive at compact, element-wise solutions of the rational function coefficients for the auto- and cross-spectrum that enable the explicit analytical computation of the PSD in dimensions $n=2,3,4$. We further present a recursive Leverrier-Faddeev-type algorithm for the exact computation of the rational function coefficients. Crucially, both solutions are free of matrix inverses. We illustrate our element-wise and recursive solutions by considering the stochastic dynamics of neural systems models, namely, FitzHugh-Nagumo ($n=2$), Hindmarsh-Rose ($n=3$), Wilson-Cowan ($n=4$), and the stabilized supralinear network ($n=22$), as well as an evolutionary game-theoretic model with mutations ($n=5,31$). We extend our approach to derive a recursive method for calculating the coefficients in the power-series expansion of the integrated covariance matrix for interacting spiking neurons modeled as Hawkes processes on arbitrary directed graphs.

For floating on water, low density is the sole necessary factor. However, it has not been clarified how to floatingly drift on fluidized granular matter. Although this problem relates to various natural phenomena such as debris flow and lunar boulder-fall traces, fundamental aspects of the floating drift on granular flow have not been revealed. Therefore, the motion of a sphere on a vibrated granular slope is experimentally investigated in this study. As a result, we find that the sinking depth of the floating sphere can be explained by a modified buoyancy model. In addition, the downstream velocity of the drifting sphere can be understood by a force balance between flow-induced pushing force and frictional resistance force. This force balance results in a nonsteady but stable floating drift on the relaxing granular slope.

We analyze the effects on the structural and electronic properties of vanadium dioxide (${\mathrm{VO}}_2$) due to adding an empirical interatomic potential within the density-functional $\mathrm{theory}+V$ ($\mathrm{DFT}+V$) framework. We use the $\mathrm{DFT}+V$ machinery founded on the extended Hubbard model to apply an empirical self-energy correction between nearest-neighbor vanadium atoms in both rutile and monoclinic phases, and for a set of structures interpolating between these two cases. We observe that imposing an explicit intersite interaction $V$ along the vanadium–vanadium chains enhances the characteristic bonding-antibonding splitting of the relevant bands in the monoclinic phase, thus favoring electronic dimerization and the formation of a bandgap. We then explore the effect of $V$ on the structural properties and the relative energies of the two phases, finding an insulating global energy minimum for the monoclinic phase, consistent with experimental observations. With increasing $V$, this minimum becomes deeper relative to the rutile structure, and the transition from the metallic to the insulating state becomes sharper. We also analyze the effect of applying the $+V$ correction either to all or only to selected vanadium–vanadium pairs and both in the monoclinic as well as the metallic rutile phase. Our results suggest that $\mathrm{DFT}+V$ can indeed serve as a computationally inexpensive unbiased way of modeling ${\mathrm{VO}}_2$ which is well suited for studies that, e.g., require large system sizes.

We report on strong field ionization of S- and R-propylene oxide in circularly polarized two-color laser fields. We find that the relative helicity of the two single-color laser fields affects the photoelectron circular dichroism (PECD). Further, we observe that PECD is modulated as a function of the subcycle release time of the electron. Our experimental observations are successfully described by a heuristic model based on electrons in chiral initial states, which are selectively liberated by the laser field and, after tunneling, interact with an achiral Coulomb potential.

Differentiable models of physical systems provide a powerful platform for gradient-based algorithms, with particular impact on parameter estimation and optimal control. Quantum systems present a particular challenge for such characterization and control, owing to their inherently stochastic nature and sensitivity to environmental parameters. To address this challenge, we present a versatile differentiable quantum master equation solver facilitating direct computation of steady-state solutions, and incorporate this solver into a framework for device characterization capable of dealing with additional nondifferentiable parameters. Our approach utilizes gradient-based optimization and Bayesian inference to provide estimates and uncertainties in quantum device parameters. To showcase our approach, we consider steady-state charge transport through electrostatically defined quantum dots. Using simulated data, we demonstrate efficient estimation of parameters for a single quantum dot, and model selection as well as the capability of our solver to compute time evolution for a double quantum dot system. Our differentiable solver stands to widen the impact of physics-aware machine learning algorithms on quantum devices for characterization and control.

The phase response curve (PRC) is crucial in elucidating the synchronization characteristics of nonlinear oscillators under the influence of external forces. Oscillatory phenomena in nature often consist of an ensemble of multiple oscillators, which complicates the measurement of individual oscillator PRCs. A prior study introduced a technique for estimating individual PRCs from the singularity response (SR)—the reaction of an ensemble of desynchronized oscillators without couplings. However, the utility of this method is somewhat limited, as it considers only the first harmonic of the PRC. The current study demonstrates that the detailed contour of the PRC can be ascertained by employing the higher harmonics of the SR.

Thouless pumping enables the transport of particles in a one-dimensional periodic potential if the potential is slowly and periodically modulated in time. The change in the position of particles after each modulation period is quantized and depends solely on the topology of the pump cycle, making it robust against perturbations. Here, we demonstrate that Thouless pumping also allows for the realization of topologically protected quantized changes of the distance between atoms if the atomic $s$-wave scattering length is properly modulated in time.

Gauge theories with matter fields in various representations play an important role in different branches of physics. Recently, it was proposed that several aspects of the pseudogap phase of cuprate superconductors near optimal doping may be explained by an emergent $\text{SU}\left(2\right)$ gauge symmetry. Around the transition with positive hole doping, one can construct a $(2+1)-\text{dimensional}$ SU(2) gauge theory coupled to four adjoint scalar fields which gives rise to a rich phase diagram with a myriad of phases having different broken symmetries. We study the phase diagram of this model on the Euclidean lattice using the hybrid Monte Carlo algorithm. We find the existence of multiple broken phases as predicted by previous mean-field studies. Depending on the quartic couplings, the SU(2) gauge symmetry is broken down either to U(1) or ${\mathbb{Z}}_2$ in the perturbative description of the model. We further study the confinement-deconfinement transition in this theory, and find that both the broken phases are deconfining in the range of volumes that we studied. However, there exists a marked difference in the behavior of the Polyakov loop between the two phases.

Thermometry is a fundamental parameter estimation problem that is crucial for the advancement of natural sciences. One widely adopted approach to address this issue is the local thermometry theory, which employs classical and quantum Cramér-Rao bounds as benchmarks for thermometric precision. However, this theory is constrained to decrease temperature fluctuations around a known temperature value, hardly tackling the precision thermometry problem over a wide temperature range. To overcome this limitation, we derive two basic bounds on thermometry precision within a global framework, i.e., classical and quantum optimal biased bounds. By implementing energy measurements on a thermal equilibrium system, the quantum optimal biased bound can be saturated. Furthermore, we demonstrate their thermometry performance through two specific applications: a noninteracting spin-$1/2$ gas and a thermalized quantum harmonic oscillator. Our results indicate that, compared to local thermometry, global thermometry provides superior temperature estimation performance. Notably, global error bound approaches its local approximation under asymptotic cases.

We consider optical response in multiband, multilayer two-dimensional superconductors. Within a simple model, we show that linear response to AC gating can detect collective modes of the condensate, such as Leggett and clapping modes. We show how trigonal warping of the superconducting order parameter can help facilitate detection of clapping modes. Taking rhombohedral trilayer graphene as an example, we consider several possible pairing mechanisms and show that all-electronic mechanisms may produce in-gap clapping modes. These modes, if present, should be detectable in the absorption of microwaves applied via the gate electrodes, which are necessary to enable superconductivity in this and many other settings; their detection would constitute strong evidence for unconventional pairing. Last, we show that absorption at frequencies above the superconducting gap $2\left|\mathrm{\Delta }\right|$ also contains a wealth of information about the gap structure. Our results suggest that linear spectroscopy can be a powerful tool for the characterization of unconventional two-dimensional superconductors.

We design and implement quantum circuits for the simulation of the one-dimensional wave equation on the Quantinuum H1-1 quantum computer. The circuit depth of our approach scales as $O\left(n^2\right)$ for $n$ qubits representing the solution on $2^n$ grid points, and leads to infidelities of $O\left(2^{-4n}{t}^2\right)$ for simulation time $t$ assuming smooth initial conditions. By varying the qubit count we study the interplay between the algorithmic and physical gate errors to identify the optimal working point of minimum total error. Our approach to simulating the wave equation can be used with appropriate state preparation algorithms across different quantum processors and serve as an application-oriented benchmark.

Ultrafast optical excitations allow creating new metastable and hidden states in quantum materials. However, the fundamental material properties required to support new emergent order are largely unknown. Here, we show for two colossal magnetoresistive (CMR) manganites that electronic phase separation (EPS) strongly favors nonthermal behavior and exploit this to stabilize an optically induced conducting state. Our results shed light on the role of EPS in the optical control of CMR manganites and provide guidance for the design of materials that can exhibit nonequilibrium states of matter.

We propose a network-model realization of magnetic higher-order topological phases (HOTPs) in the presence of the combined space-time symmetry $C_4\mathcal{T}$—the product of a fourfold rotation and time-reversal symmetry. We show that the system possesses two types of HOTPs. The first type, analogous to Floquet topology, generates a total of eight corner modes at 0 or $\pi$ eigenphase, while the second type, hidden behind a weak topological phase, yields a unique phase with eight corner modes at $\pm \pi /2$ eigenphase (after gapping out the counterpropagating edge states), arising from the product of particle-hole and phase-rotation symmetry. By using a bulk ${\mathbb{Z}}_4$ topological index $\left(Q\right)$, we found both HOTPs have $Q=2$, whereas $Q=0$ for the trivial and the conventional weak topological phase. Together with a ${\mathbb{Z}}_2$ topological index associated with the reflection matrix, we are able to fully distinguish all phases. Our work motivates further studies on magnetic topological phases and symmetry-protected $2\pi /n$ boundary modes, as well as suggesting that such phases may find their experimental realization in coupled-ring-resonator networks.

Sonic and photonic topological insulators that host topological edge states offer promising potentials for the resilient control of acoustic and electromagnetic waves, respectively. Despite the great progress on sonic or photonic topological insulators, the research of their integration, i.e., the phoxonic topological insulator, is less explored. In this work, we propose a phoxonic topological insulator that hosts acoustic and dual-polarization photonic helical edge states simultaneously. In specific, we first design a glide-symmetric phoxonic crystal with concurrent sonic and dual-polarization photonic bandgaps via the topology optimization method. Then by choosing two different unit cells from the optimized phoxonic crystal and assembling them to create a domain-wall interface, a phoxonic topological insulator that supports two pairs of gapless helical edge states within both the sonic and photonic bandgaps is constructed. Pseudospin-locked unidirectional transmissions and robust manipulations of helical edge states are demonstrated for acoustic and dual-polarization electromagnetic waves simultaneously in the proposed phoxonic topological insulator. The designed phoxonic topological insulator opens new avenues for developing topological photoacoustic devices, enabling the reliable management of both acoustic and electromagnetic waves, as well as the investigation of their interplay.

High-brightness megahertz-rate electron beams are highly desired for cutting-edge applications in many areas of science. Photocathode electron guns capable of generating such beams with low dark current remain to be a challenging field. In this paper, we report breakthroughs with a hybrid gun combining a direct-current gap and a superconducting radio-frequency (SRF) cavity. The gun, employing ${\mathrm{K}}_2\mathrm{CsSb}$ photocathodes driven by a green laser, delivers a few MeV electron beam at 1 and 81.25 MHz rates with an average current up to 3 mA and a dark current several orders lower than current normal conducting continuous-wave guns. Emittance compensation and multipole field corrections have been applied to achieve a high-quality beam. The achievement will inspire the development of high-brightness SRF guns and promote megahertz-rate beam applications including coherent linac light sources and ultrafast electron diffraction/microscopy.

We examine an effectively one-electron system with three positive nuclei composed of a ${}^{87}\mathrm{Rb}^{*}$ Rydberg atom interacting with a pair of ${}^{87}\mathrm{Rb}^{+}$ ions and predict the existence of metastable vibrationally bound states of ${}^{87}\mathrm{Rb}_3^{2+}$. These molecules are long-range trimers whose stability rests on the presence of core-shell electrons and favorable scaling of the Rydberg atom's quadrupole moment with the principal quantum number $n$. Unlike recently observed ion-Rydberg dimers, whose binding is due to internal flipping of the Rydberg atom's dipole moment, the binding of ${}^{87}\mathrm{Rb}_3^{2+}$ arises from the interaction of the ions with the Rydberg atom's quadrupole moment. The stability of these trimers is highly sensitive to $n$. For $n\le 35$, we estimate that the lifetime of the bound states should be limited by intercore tunneling of the Rydberg electron, which creates an instability in the system. However, we predict that the rate of this process decreases significantly with $n$, such that already for $n=38$ it is comparable in magnitude to the rate of spontaneous emission of the Rydberg state. The decreasing depth of the binding potential at larger $n$ will further lead to an increase in the tunneling rate of the vibrational states from the molecular binding potential to dissociative regions of the adiabatic potential energy surface. Nonetheless, at $n=38$, this mechanism is only relevant for the highest-excited vibrational states in the binding potential.

Quantum mechanics empowers the emergence of quantum advantages in various fields, including quantum algorithms. Quantum PageRank is a promising tool for a future quantum internet. Recently, arbitrary phase rotations (APRs) have been introduced in the underlying Szegedy's quantum walk of the quantum PageRank algorithm. In this work we thoroughly study the role APR plays in quantum PageRank. We discover the versatility resulting from quantumness. Specifically, we discover the emergence of a cluster phenomenon in rankings considering the rotation phases, i.e., the existence of similar clusters in the distribution of the rankings and their fidelity with the corresponding classical PageRanks, the ranking distribution variance, the coherence and entanglement of PageRank states, and the power-law parameter in the ranking distributions on a scale-free network concerning the two rotation phases. Furthermore, we propose an alternate quantum PageRank with APR which provides an extra tunnel for the analysis of PageRank. We also study the PageRank on the trackback graph of a scale-free graph for the investigation of network information traffic tracking. We demonstrate the rich cluster diversity formed in our alternate quantum PageRank, which offers a novel perspective on the quantum versatility of PageRank. Our results present the quantum-enabled perspective for PageRanking and shed light on the design and application of practical quantum PageRank algorithms.

The magnetic skyrmion is described by one control parameter and one length scale. We study the two extreme limits of the control parameter, infinitely large and vanishing, and find that the magnetic skyrmion becomes a “restricted” magnetic skyrmion and an $\mathrm{O}\left(3\right)$ sigma model lump, respectively. Depending on the potential under consideration, the restricted limit manifests differently. In the case of the Zeeman term, the restricted magnetic skyrmion becomes a “supercompacton” that develops a discontinuity, whereas for the Zeeman term to the power $\frac{3}{2}$ it becomes a normal compacton. In both the lump and the restricted limit the solution is given in exact explicit form. We observe that the case of the Zeeman term squared, which can also be understood as a special combination of the Zeeman term and the easy-plane potential (realizable in the laboratory), the analytically exact solution for all values of the coupling, including the Bogomol'nyi-Prasad-Sommerfield case, is also of the lump type. Finally, we notice that certain materials (e.g., ${\mathrm{Fe}}_{1\text{−}x}{\mathrm{Co}}_x\mathrm{Si}$ or ${\mathrm{Mn}}_{1\text{−}x}{\mathrm{Fe}}_x\mathrm{Ge}$) have a rather large control parameter $\epsilon$ of order 100, making the restricted limit a suitable rough approximation.