Yujun Zheng

It is crucial to understand the role of polarization and the built-in electric field in heterostructures of two-dimensional materials, as these factors significantly affect carrier dynamics, interfacial properties, and device performance. Here, we combine first-principles calculations with nonadiabatic molecular dynamics simulations to investigate the electronic structure and excited-state carrier dynamics of MoS2/MoSSe heterostructures. We show that the interplay between the intrinsic polarization of Janus MoSSe and the interface-induced electric field strongly modulates interlayer charge transfer. This dual-field coupling drives a transition between type-I and type-II band alignments and switches the dominant carrier relaxation pathways from intralayer recombination to interlayer charge separation. Carrier relaxation is further governed by the interplay between nonadiabatic coupling and phonon-assisted transitions. These results identify polarity reversal as an effective strategy for tuning charge-transfer pathways and excited-state dynamics in van der Waals heterostructures, and provide guidance for designing two-dimensional optoelectronic and photocatalytic materials.

Geometric quantum gates play crucial role in quantum computation, and the diffident types of geometric gates are constructed, including conventional and unconventional geometric gates. The physical natures of the conventional geometric gates with zero dynamical phase are investigated widely. In this paper, we analyze the physical natures of the unconventional geometric gates, and present the unconventional geometric gate is related with the Levi–Civita connection. We establish its physical constraint, and demonstrate the results by employing two‐level system.

Two-dimensional (2D) ferromagnetic (FM) materials hold great promise for advanced spintronic devices, particularly those featuring large perpendicular magnetic anisotropy (PMA) and high Curie temperature (T_c). Here, based on the first-principles calculations and Monte Carlo (MC) simulations, we examine the stability, electronic structure and magnetic properties of the FePd₂Te₂ at the 2D limit, whose nanosheets have been successfully exfoliated in experiments. Notably, the FePd₂Te₂ monolayer featuring one-dimensional (1D) Fe zigzag chains exhibits a T_c of 242 K, which is significantly higher than that of the bulk FePd₂Te₂ (93K). Strain engineering further enhances the T_c to 569 K under 5% compressive strain, driven by stronger FM coupling between the Fe atoms in the 1D zigzag chains. Furthermore, this compressive strain also results in a transformation of the MAE from the in-plane to the out-of-plane direction. Our work provides a valuable strategy to control both spin direction and the Curie temperature, which enables 2D FePd₂Te₂ to be applied in spintronic devices at room temperature, thereby establishing a more stable foundation for achieving superior performance.

We theoretically investigate the statistical properties of photon emission of a driven two-level single-molecule system undergoing spectral diffusion induced by nonequilibrium environmental fluctuations. Within the framework of the generating function method and the stochastic Liouville equation, we analyze the influence of the nonequilibrium characteristics of environmental fluctuations, respectively, governed by nonstationary Ornstein–Uhlenbeck noise and random telegraph noise on the photon counting statistics of the driven single-molecule system. In the slow modulation limit of spectral diffusion, the intensity and statistical fluctuations of photon emission depend on the environmental nonequilibrium characteristics at short time scales, whereas they become independent of the nonequilibrium characteristics of environmental fluctuations in the steady state. In the fast modulation limit of spectral diffusion, neither the line shape nor the Mandel’s parameter depends on the environmental nonequilibrium characteristics owing to the rapid relaxation of environmental fluctuations. These findings not only shed light on the role of nonequilibrium environmental fluctuations in shaping the photon emission properties of single-molecule systems but also provide a basis for distinguishing between equilibrium and nonequilibrium characteristics of environmental fluctuations in experimental measurements.

In this study, taking MoXY (X/Y = S, Se, Te) monolayers as an example, we systematically investigate the regulatory role of the polarization induced by elemental variation in the properties of low-dimensional materials, using first-principles calculations combined with nonadiabatic molecular dynamics (NAMD) simulations. The polarization can significantly affect the band edge positions and photocatalytic performance of asymmetric MoXY and effectively lower the reaction energy barriers, thus facilitating photocatalytic water-splitting. In terms of NAMD, this polarization can alter nonadiabatic coupling strength and govern excited-state carrier properties. In addition, the effects of temperature and electron–phonon coupling on the carrier lifetime of the system are also taken into account in this study. This study provides a new theoretical perspective for the selection of photocatalytic materials and offers valuable insights into investigating the manipulation of carrier dynamics in two-dimensional materials.

We introduce a novel two-dimensional ferromagnetic valley material, TiSeCl, and confirm its potential to enable valley-related multichannel Hall effects within a stable two-dimensional ferromagnetic semiconductor. The intrinsic lack of spatial inversion symmetry and time-reversal symmetry in the TiSeCl structure allows for spontaneous valley polarization, making it highly advantageous for practical valley manipulation since its intrinsic valley polarization values can reach 95 meV. The strong spin–orbit coupling effects in the TiSeCl monolayer result in distinct Berry curvatures and opposing signals in the +K and −K valleys, leading to an anomalous valley Hall effect. Furthermore, under a 1.25% tensile strain, the TiSeCl monolayer undergoes band inversion, leading to a topological phase transition from the ferromagnetic valley state to the semivalley metal state and subsequently to a valley-polarized quantum anomalous Hall phase. This study expands our understanding of valley properties in two-dimensional materials and provides theoretical guidance for valley manipulation in valley electronics.

Graphene-like CrP ₃ exhibits ferromagnetism. Under tensile strain, it transitions from a magnetic half-metal to a magnetic semiconductor, with the band gap showing quantization as the magnetic moment rotates.

We apply the trajectory formulation to analyze the anomalous dynamics of cold atoms in an optical lattice. The phase space probability density function of cold atoms, their dynamics, and the mechanism of dynamic evolution from an initial Gaussian distribution to a power-law distribution are analyzed. The results of the trajectory formulation are in good agreement with the previously reported experimental results for the exponent of position variance for a long time and the position–momentum correlation. The self-similar natures of trajectories in phase space are found for Lévy distributions. Our results unify the raw moments that can be expressed as the summation of a number of independent, identically distributed variables and the anomalous dynamics, which holds promise for an intuitive interpretation anomalous behavior and their kinetic mechanisms from initial Gaussian to anomalous distributions for a long time.