We investigate the medium modifications of momentum splitting fraction and groomed jet radius with both dynamical grooming and soft drop algorithms in heavy-ion collisions. In the calculation, the partonic spectrum of initial hard scattering in p+p collisions is provided by the event generator PYTHIA8, and the energy loss of fast parton traversing in a hot/dense quantum-chromodynamic medium is simulated with the linear Boltzmann transport model. We predict the normalized distributions of the groomed jet radius $\theta_{\rm g}$ and momentum splitting fraction $z_{\rm g}$ with the dynamical grooming algorithm in Pb+Pb collisions at $\sqrt{s_{\scriptscriptstyle{\rm NN}}}$ = 5.02 TeV, then compare these quantities in dynamical grooming at $a=0.1$, with that in soft drop at $z_{\mathrm{cut}} = 0.1$ and $\beta = 0$. It is found that the normalized distribution ratios Pb+Pb/p+p with respect to $z_{\rm g}$ in $z_{\mathrm{cut}} = 0.1$, $\beta = 0$ soft drop case are close to unity, those in $a=0.1$ dynamical grooming case show enhancement at small $z_{\rm g}$, and Pb+Pb/p+p with respect to $\theta_{\rm g}$ in the dynamical grooming case demonstrate weaker modification than those in the soft drop counterparts. We further calculate the groomed jet number averaged momentum splitting fraction $\langle z_{\rm g} \rangle_{\rm jets}$ and averaged groomed jet radius $\langle \theta_{\rm g} \rangle_{\rm jets}$ in p+p and A+A for both grooming cases in three $p^{\rm ch~jet}_{\scriptscriptstyle{\rm T}}$ intervals, and find that the originally generated well balanced groomed jets will become more momentum imbalanced and jet size less narrowed due to jet quenching, and weaker medium modification of $z_{\rm g}$ and $\theta_{\rm g}$ in the $a =0.1$ dynamical grooming case than in the soft drop counterparts.

Nondipole effects are ubiquitous and crucial in light-matter interaction. However, they are too weak to be directly observed. In strong-field physics, motion of electrons is mainly confined in transverse plane of light fields, which suppresses the significance of nondipole effects. Here, we present a theoretical study on enhancing and controlling the nondipole effect by using the synthesized two perpendicularly propagating laser fields. We calculate the three-dimensional photoelectron momentum distributions of strong-field tunneling ionization of hydrogen atoms using the classical trajectory Monte Carlo model and show that the nondipole effects are noticeably enhanced in such laser fields due to their remarkable influences on the sub-cycle photoelectron dynamics. In particular, we reveal that the magnitudes of the magnetic and electric components of nondipole effects can be separately controlled by modulating the ellipticity and amplitude of driving laser fields. This novel scenario holds promising applications for future studies with ultrafast structured light fields.

FUNDAMENTAL AREAS OF PHENOMENOLOGY(INCLUDING APPLICATIONS)

The physical concept of synthetic dimensions has recently been introduced into optics. The fundamental physics and applications are not yet fully understood, and this report explores an approach to optical neural networks using synthetic dimension in time domain, by theoretically proposing to utilize a single resonator network, where the arrival times of optical pulses are interconnected to construct a temporal synthetic dimension. The set of pulses in each roundtrip therefore provides the sites in each layer in the optical neural network, and can be linearly transformed with splitters and delay lines, including the phase modulators, when pulses circulate inside the network. Such linear transformation can be arbitrarily controlled by applied modulation phases, which serve as the building block of the neural network together with a nonlinear component for pulses. We validate the functionality of the proposed optical neural network for the deep learning purpose with examples handwritten digit recognition and optical pulse train distribution classification problems. This proof of principle computational work explores the new concept of developing a photonics-based machine learning in a single ring network using synthetic dimensions, which allows flexibility and easiness of reconfiguration with complex functionality in achieving desired optical tasks.

CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES

Phonons are the primary heat carriers in non-metallic solids. In compositionally heterogeneous materials, the thermal properties are believed to be mainly governed by the disrupted phonon transport due to mass disorder and strain fluctuations, while the effects of compositional fluctuation induced local phonon states are usually ignored. Here, by scanning transmission electron microscopy electron energy loss spectroscopy and sophisticated calculations, we identify the vibrational properties of ingredient-dependent interface phonon modes in Al$_{x}$Ga$_{1-x}$N and quantify their various contributions to the local interface thermal conductance. We demonstrate that atomic-scale compositional fluctuation has significant influence on the vibrational thermodynamic properties, highly affecting the mode ratio and vibrational amplitude of interface phonon modes and subsequently redistributing their modal contribution to the interface thermal conductance. Our work provides fundamental insights into understanding of local phonon-boundary interactions in nanoscale inhomogeneities, which reveal new opportunities for optimization of thermal properties via engineering ingredient distribution.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

The electronic evolution of Mott insulators into exotic correlated phases remains puzzling, because of electron interaction and inhomogeneity. Introduction of individual imperfections in Mott insulators could help capture the main mechanism and serve as a basis to understand the evolution. Here we utilize scanning tunneling microscopy to probe the atomic scale electronic structure of the spin-orbit-coupling assisted Mott insulator Sr$_{3}$Ir$_{2}$O$_{7}$. It is found that the tunneling spectra exhibit a homogeneous Mott gap in defect-free regions, but near the oxygen vacancy in the rotated IrO$_{2}$ plane the local Mott gap size is significantly enhanced. We attribute the enhanced gap to the locally reduced hopping integral between the 5$d$ electrons of neighboring Ir sites via the bridging planar oxygen $p$ orbitals. Such bridging defects have a dramatic influence on local bandwidth, thus provide a new way to manipulate the strength of Mottness in a Mott insulator.

The simple kagome-lattice band structure possesses Dirac cones, flat band, and saddle point with van Hove singularities in the electronic density of states, facilitating the emergence of various electronic orders. Here we report a titanium-based kagome metal CsTi$_{3}$Bi$_{5}$ where titanium atoms form a kagome network, resembling its isostructural compound CsV$_{3}$Sb$_{5}$. Thermodynamic properties including the magnetization, resistance, and heat capacity reveal the conventional Fermi liquid behavior in the kagome metal CsTi$_{3}$Bi$_{5}$ and no signature of superconducting or charge density wave (CDW) transition anomaly down to 85 mK. Systematic angle-resolved photoemission spectroscopy measurements reveal multiple bands crossing the Fermi level, consistent with the first-principles calculations. The flat band formed by the destructive interference of hopping in the kagome lattice is observed directly. Compared to CsV$_{3}$Sb$_{5}$, the van Hove singularities are pushed far away above the Fermi level in CsTi$_{3}$Bi$_{5}$, in line with the absence of CDW. Furthermore, the first-principles calculations identify the nontrivial $\mathbb{Z}_2$ topological properties for those bands crossing the Fermi level, accompanied by several local band inversions. Our results suppose CsTi$_{3}$Bi$_{5}$ as a complementary platform to explore the superconductivity and nontrivial band topology.

The origin of the quantum superconductor to metal transition at zero temperature in two-dimensional superconductors is still an open problem, which has caused intensely discussion. Here, we report the observation of a quantum superconductor-to-metal transition in LaAlO$_{3}$/KTaO$_{3}$ (111) interface, driven by magnetic field. When a small magnetic field perpendicular to the film plane is applied, the residual saturated resistance is observed, indicating the emergence of an anomalous metallic state associated with a failed superconductor. The dependence of saturated resistance on magnetic field at low temperature indicates that the observed metal state is a Bose metal state. From our findings, magnetic field regulating LaAlO$_{3}$/KTaO$_{3}$ (111) interface emerges as a platform to scrutinize the details of the anomalous metallic state in a controllable way.

The one-band $t$–$J$ model captures strong correlations in cuprate high-temperature superconductors. It accounts for the various intertwined spin and charge orders, and the superconductivity in the phase diagrams. To see the correlation effect on the intertwined orders, we implement the density matrix renormalization group method to simulate the $t$–$J$ model in a small $J$ case with $t/J=10$, which is in a deeper Mott region than that with $t/J\simeq3$ in cuprate superconducting compounds. We examine the results on a six-leg lattice with both the nearest and next-nearest-neighbor hoppings and antiferromagnetic coupling, and find the absence of superconductivity and enhanced intertwined spin and charge orders in the phase diagram. Besides the stripe phases, we find a new SDW + CDW phase in which the spin modulation is a $(\pi, \pi)$ antiferromagnetism, while the wavelength of the charge modulation is shorter than that of the stripe phases. Our results suggest the enhanced intertwined orders and suppressed superconductivity in the deep Mott region.

Seeking new order parameters and the related broken symmetry and studying their relationship with phase transition have been important topics in condensed matter physics. Here, by using spin- and angle-resolved photoemission spectroscopy, we confirm the helical spin texture caused by spin-layer locking in the nodal region in the cuprate superconductor Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ and discover the anisotropy of spin polarizations at nodes along $\varGamma$–$X$ and $\varGamma$–$Y$ directions. The breaking of $C_{4}$ rotational symmetry in electronic spin texture may give deeper insights into understanding the ground state of cuprate superconductors.

Research of vortex properties in type-II superconductors is of great importance for potential applications and fundamental physics. Here, we present a comprehensive study of the critical current density $J_{\rm c}$, vortex pinning, and phase diagram of NaCl-type InTe$_{1- x}$Se$_{x}$ ($x = 0$, 0.1, 0.2) superconductors synthesized by high-pressure technique. Our studies reveal that the values of $J_{\rm c}$ calculated by the Bean model exceed $10^{4}$ A/cm$^{2}$ in the InTe$_{1- x}$Se$_{x}$ system, signifying good potential for applications. The magnetic hysteresis loops (MHLs) show an asymmetric characteristic at various degrees, which is associated with the surface barrier. Intriguingly, a rare phenomenon in which the second magnetization peak in the MHLs occurs only in the field-descending branch is detected in InTe$_{0.9}$Se$_{0.1}$. Such an anomalous behavior has not been observed before and can be described by considering the respective roles of the surface barrier and bulk pinning in the field-ascending and field-descending branches. By analyzing the pinning force density versus reduced field, the pinning mechanisms are studied in detail in the framework of the Dew-Hughes model. Finally, combining the results of resistivity and magnetization measurements, the vortex phase diagrams are constructed and discussed.

We explore the imaginary-time relaxation dynamics near quantum critical points with semi-ordered initial states. Different from the case with homogeneous ordered initial states, in which the order parameter $M$ decays homogeneously as $M\propto \tau^{-\beta/\nu z}$, here $M$ depends on the location $x$, showing rich scaling behaviors. Similar to the classical relaxation dynamics with an initial domain wall in model A, which describes the purely dissipative dynamics, here as the imaginary time evolves, the domain wall expands into an interfacial region with growing size. In the interfacial region, the local order parameter decays as $M\propto \tau^{-\beta_1/\nu z}$, with $\beta_1$ being an additional dynamic critical exponent. Far away from the interfacial region the local order parameter decays as $M\propto \tau^{-\beta/\nu z}$ in the short-time stage, then crosses over to the scaling behavior of $M\propto \tau^{-\beta_1/\nu z}$ when the location $x$ is absorbed in the interfacial region. A full scaling form characterizing these scaling properties is developed. The quantum Ising model in both one and two dimensions are taken as examples to verify the scaling theory. In addition, we find that for the quantum Ising model the scaling function is an analytical function and $\beta_1$ is not an independent exponent.

We report the interplay between two different topological phases in condensed matter physics, the magnetic chiral domain wall (DW), and the quantum anomalous Hall (QAH) effect. It is shown that the chiral DW driven by Dzyaloshinskii–Moriya interaction can divide the uniform domain into several zones where the neighboring zone possesses opposite quantized Hall conductance. The separated domain with a chiral edge state (CES) can be continuously modified by external magnetic field-induced domain expansion and thermal fluctuation, which gives rise to the reconfigurable QAH effect. More interestingly, we show that the position of CES can be tuned by spin current driven chiral DW motion. Several two-dimensional magnets with high Curie temperature and large topological band gaps are proposed for realizing these phenomena. The present work thus reveals the possibility of chiral DW controllable QAH effects.

CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

We fabricated monolayer n-type two-dimensional crystalline semiconducting films with millimeter-sized areas and remarkable morphological uniformity using an antisolvent-confined spin-coating method. The antisolvent can cause a downstream Marangoni flow, which improves the film morphologies. The deposited crystalline monolayer films exhibit excellent thermal stabilities after annealing, which reveals the annealing-induced enhancement of crystallinity. The transistors based on the n-type monolayer crystalline films show linear output characteristics and superior electron mobilities. The improved charge injection between monolayer films and Au electrodes results from the energy level shift as the films decrease to the monolayer, which leads to a lower injection barrier. This work demonstrates a promising method for fabricating air-stable, low-cost, high-performance, and large-area organic electronics.

Laser interferometry is an important technique for ultrasensitive detection of motion and displacement. We push the limit of laser interferometry through noise optimization and device engineering. The contribution of noises other than shot noise is reduced from 92.6% to 62.4%, demonstrating the possibility towards shot-noise-limited measurement. Using noise thermometry, we quantify the laser heating effect and determine the range of laser power values for room-temperature measurements. With detailed analysis and optimization of signal transduction, we achieve 1.2 fm/Hz$^{1/2}$ displacement measurement sensitivity at room temperature in two-dimensional (2D) CaNb$_{2}$O$_{6}$ nanomechanical resonators, the best value reported to date among all resonators based on 2D materials. Our work demonstrates a possible pathway towards quantum-noise-limited measurement at room temperature.

On the basis of novel properties of ferroelectric conducting domain walls, the domain wall nanoelectronics emerges and provides a brand-new dimension for the development of high-density, high-speed and energy-efficient nanodevices. For in-memory computing, three-terminal devices with both logic and memory functions such as transistors purely based on ferroelectric domain walls are urgently required. Here, a prototype ferroelectric domain-wall transistor with a well-designed coplanar electrode geometry is demonstrated on epitaxial BiFeO$_{3}$ thin films. For the logic function, the current switching between on/off states of the transistor depends on the creation or elimination of conducting domain walls between drain and source electrodes. For the data storage, the transistor can maintain nonvolatile on/off states after the write/erase operations, providing an innovative approach for the development of the domain wall nanoelectronics.