Frontiers of Physics最新文献

Two-dimensional (2D) heterostructures have shown great potential in advanced photovoltaics due to their restrained carrier recombination, prolonged exciton lifetime and improved light absorption. Herein, a 2D polarized heterostructure is constructed between Janus MoSSe and MoTe₂ monolayers and is systematically investigated via first-principles calculations. Electronically, the valence band and conduction band of the MoSSe–MoTe₂ (MoSeS–MoTe₂) are contributed by MoTe₂ and MoSSe layers, respectively, and its bandgap is 0.71 (0.03) eV. A built-in electric field pointing from MoTe₂ to MoSSe layers appears at the interface of heterostructures due to the interlayer carrier redistribution. Notably, the band alignment and built-in electric field make it a direct z-scheme heterostructure, benefiting the separation of photogenerated electron-hole pairs. Besides, the electronic structure and interlayer carrier reconstruction can be readily controlled by reversing the electric polarization of the MoSSe layer. Furthermore, the light absorption of the MoSSe/MoTe₂ heterostructure is also improved in comparison with the separated monolayers. Consequently, in this work, a new z-scheme polarized heterostructure with polarization-controllable optoelectronic properties is designed for highly efficient optoelectronics.

Distributed quantum computation has gained extensive attention. In this paper, we consider a search problem that includes only one target item in the unordered database. After that, we propose a distributed exact Grover’s algorithm (DEGA), which decomposes the original search problem into ⌊n/2⌋ parts. Specifically, (i) our algorithm is as exact as the modified version of Grover’s algorithm by Long, which means the theoretical probability of finding the objective state is 100%; (ii) the actual depth of our circuit is 8(n mod 2) + 9, which is less than the circuit depths of the original and modified Grover’s algorithms, (1 + 8leftlfloor {{pi over 4}sqrt {{2^n}} } rightrfloor ) and (9 + 8leftlfloor {{pi over 4}sqrt {{2^n}} - {1 over 2}} rightrfloor ), respectively. It only depends on the parity of n, and it is not deepened as n increases; (iii) we provide particular situations of the DEGA on MindQuantum (a quantum software) to demonstrate the practicality and validity of our method. Since our circuit is shallower, it will be more resistant to the depolarization channel noise.

The direct observation of gravitational waves (GWs) opens a new window for exploring new physics from quanta to cosmos and provides a new tool for probing the evolution of universe. GWs detection in space covers a broad spectrum ranging over more than four orders of magnitude and enables us to study rich physical and astronomical phenomena. Taiji is a proposed space-based gravitational wave (GW) detection mission that will be launched in the 2030s. Taiji will be exposed to numerous overlapping and persistent GW signals buried in the foreground and background, posing various data analysis challenges. In order to empower potential scientific discoveries, the Mock Laser Interferometer Space Antenna (LISA) data challenge and the LISA data challenge (LDC) were developed. While LDC provides a baseline framework, the first LDC needs to be updated with more realistic simulations and adjusted detector responses for Taiji’s constellation. In this paper, we review the scientific objectives and the roadmap for Taiji, as well as the technical difficulties in data analysis and the data generation strategy, and present the associated data challenges. In contrast to LDC, we utilize second-order Keplerian orbit and second-generation time delay interferometry techniques. Additionally, we employ a new model for the extreme-mass-ratio inspiral waveform and stochastic GW background spectrum, which enables us to test general relativity and measure the non-Gaussianity of curvature perturbations. Furthermore, we present a comprehensive showcase of parameter estimation using a toy dataset. This showcase not only demonstrates the scientific potential of the Taiji data challenge (TDC) but also serves to validate the effectiveness of the pipeline. As the first data challenge for Taiji, we aim to build an open ground for data analysis related to Taiji sources and sciences. More details can be found on the official website (taiji-tdc.ictp-ap.org).

The combination of multi-component Bose–Einstein condensates (BECs) and phase imprinting techniques provides an ideal platform for exploring nonlinear dynamics and investigating the quantum transport properties of superfluids. In this paper, we study abundant density structures and corresponding dynamics of phase-separated binary Bose–Einstein condensates with phase-imprinted single vortex or vortex dipole. By adjusting the ratio between the inter-species and intra-species interactions, and the locations of the phase singularities, the typical density profiles such as ball-shell structures, crescent-gibbous structures, Matryoshka-like structures, sector-sector structures and sandwich-type structures appear, and the phase diagrams are obtained. The dynamics of these structures exhibit diverse properties, including the penetration of vortex dipoles, emergence of halfvortex dipoles, co-rotation of sectors, and oscillation between sectors. The pinning effects induced by a potential defect are also discussed, which is useful for controlling and manipulating individual quantum states.

Photodetectors based on two-dimensional (2D) semiconductors have attracted many research interests owing to their excellent optoelectronic characteristics and application potential for highly integrated applications. However, the unique morphology of 2D materials also restricts the further improvement of the device performance, as the carrier transport is very susceptible to intrinsic and extrinsic environment of the materials. Here, we report the highest responsivity (172 A/W) achieved so far for a PbI₂-based photodetector at room temperature, which is an order of magnitude higher than previously reported. Thermal scanning probe lithography (t-SPL) was used to pattern electrodes to realize the ultrashort channel (~60 nm) in the device. The shortening of the channel length greatly reduces the probability of the photo-generated carriers being scattered during the transport process, which increases the photocurrent density and thus the responsivity. Our work shows that the combination of emerging processing technologies and 2D materials is an effective route to shrink device size and improve device performance.

The two-dimensional (2D) bulk photovoltaic effect (BPVE) is a cornerstone for future highly efficient 2D solar cells and optoelectronics. The ferromagnetic semiconductor 2H-FeCl₂ is shown to realize a new type of BPVE in which spatial inversion (P), time reversal (T), and space–time reversal (PT) symmetries are broken (PT-broken). Using density functional theory and perturbation theory, we show that 2H-FeCl₂ exhibits giant photocurrents, photo-spin-currents, and photo-orbital-currents under illumination by linearly polarized light. The injection-like and shift-like photocurrents coexist and propagate in different directions. The material also demonstrates substantial photoconductance, photo-spin-conductance, and photo-orbital-conductance, with magnitudes up to 4650 (nm·µA/V²), 4620 [nm·µA/V²ħ/(2e)], and 6450 (nm·µA/V²ħ/e), respectively. Furthermore, the injection-currents, shift-spin-currents, and shift-orbital-currents can be readily switched via rotating the magnetizations of 2H-FeCl₂. These results demonstrate the superior performance and intriguing control of a new type of BPVE in 2H-FeCl₂.

Whereas topological symmetries have been recognized as crucially important to the exploration of synchronization patterns in complex networks of coupled dynamical oscillators, the identification of the symmetries in large-size complex networks remains as a challenge. Additionally, even though the topological symmetries of a complex network are known, it is still not clear how the system dynamics is transited among different synchronization patterns with respect to the coupling strength of the oscillators. We propose here the framework of eigenvector-based analysis to identify the synchronization patterns in the general complex networks and, incorporating the conventional method of eigenvalue-based analysis, investigate the emergence and transition of the cluster synchronization states. We are able to argue and demonstrate that, without a prior knowledge of the network symmetries, the method is able to predict not only all the cluster synchronization states observable in the network, but also the critical couplings where the states become stable and the sequence of these states in the process of synchronization transition. The efficacy and generality of the proposed method are verified by different network models of coupled chaotic oscillators, including artificial networks of perfect symmetries and empirical networks of non-perfect symmetries. The new framework paves a way to the investigation of synchronization patterns in large-size, general complex networks.

In the last decade, chiral symmetry in atomic nuclei has attracted significant attention and become one of the hot topics in current nuclear physics frontiers. This paper provides a review of experimental studies for nuclear chirality in China. In particular, the experimental setups, chiral mass regions, lifetime measurements, and simultaneous breaking of chirality and other symmetries are discussed in detail. These studies found a new chiral mass region (A ≈ 80), extended the boundaries of the A ≈ 100 and 130 chiral mass regions, and tested the chiral geometry of ¹³⁰Cs, ¹⁰⁶Ag, ⁸⁰Br and ⁷⁶Br by lifetime measurements. In addition, simultaneous breaking of chirality and other symmetries have been studied in ⁷⁴As, ⁷⁶Br, ⁷⁸Br, ⁸⁰Br, ⁸¹Kr and ¹³¹Ba.

Plasmonic resonators are widely used for the manipulation of light on subwavelength scales through the near-field electromagnetic wave produced by the collective oscillation of free electrons within metallic systems, well known as the surface plasmon (SP). The non-radiative decay of the surface plasmon can excite a plasmonic hot electron. This review article systematically describes the excitation progress and basic properities of SPs and plasmonic hot electrons according to recent publications. The extraction mechanism of plasmonic hot electrons via Schottky conjunction to an adjacent semiconductor is also illustrated. Also, a calculation model of hot electron density is given, where the efficiency of hot-electron excitation, transport and extraction is discussed. We believe that plasmonic hot electrons have a huge potential in the future development of optoelectronic systems and devices.

Recently, nonadiabatic geometric quantum computation has been received great attentions, due to its fast operation and intrinsic error resilience. However, compared with the corresponding dynamical gates, the robustness of implemented nonadiabatic geometric gates based on the conventional single-loop geometric scheme still has the same order of magnitude due to the requirement of strict multi-segment geometric controls, and the inherent geometric fault-tolerance characteristic is not fully explored. Here, we present an effective geometric scheme combined with a general dynamical-corrected technique, with which the super-robust nonadiabatic geometric quantum gates can be constructed over the conventional single-loop geometric and two-loop composite-pulse geometric strategies, in terms of resisting the systematic error, i.e., σ_x error. In addition, combined with the decoherence-free subspace (DFS) coding, the resulting geometric gates can also effectively suppress the σ_z error caused by the collective dephasing. Notably, our protocol is a general one with simple experimental setups, which can be potentially implemented in different quantum systems, such as Rydberg atoms, trapped ions and superconducting qubits. These results indicate that our scheme represents a promising way to explore large-scale fault-tolerant quantum computation.