Qi-Feng Liang

We investigated the ground-state properties and quantum phase transitions (QPTs) of an ensemble of N four-level atoms in an optical cavity, coupled to a single cavity mode and external laser fields. The system is described by an extended imbalanced Dicke model, in which the co-rotating and counter-rotating coupling terms are allowed to have different coupling strengths. We analytically identified several novel polarized phases characterized by the phase differences between the Raman laser and either the cavity field or the atomic spin excitation. Furthermore, the full phase diagram and QPTs were also revealed. Two sign-dependent coexisting phases were identified, in which the normal phase persists as a metastable state alongside the superradiant ground state. Finally, the breaking or restoration of the intrinsic symmetry in this system was addressed. It was found that, in addition to the continuous U ( 1 ) and discrete Z 2 symmetries, the system also exhibits two reflection symmetries σ v s and a central symmetry C 2 in the abstract position–momentum representation, as a discrete reflection parity–time ( PT ) symmetry and a parameter exchange symmetry T ex in the parameter space. These additional symmetries are governed by two Coxeter groups.

Strong electron-lattice coupling in 1T-MX₂ (M = Nb, Ta; X = S, Se) enables diverse quantum phenomena. Using first-principles calculations, we reveal temperature-dependent orbital textures of midgap states in monolayer 1T-NbSe₂ with a star-of-David charge-density-wave superstructure. A mere 0.1% thermal lattice expansion drives a sharp nonmagnetic-to-ferromagnetic transition. In the ferromagnetic phase, midgap states localize at the supercell center, while in the nonmagnetic phase, high-energy Rydberg-like states generate weak in-gap signals and characteristic six-petal orbital patterns. These findings resolve long-standing theory-experiment discrepancies and establish Rydberg fingerprinting as a method to probe high-energy electronic structures via low-bias scanning tunneling spectroscopy, offering new insights into coupled electronic and magnetic degrees of freedom in two-dimensional transition metal dichalcogenides.

Most Siamese‐based trackers use classification and regression to determine the target bounding box, which can be formulated as a linear matching process of the template and search region. However, this only takes into account the similarity of features while ignoring the semantic object information, resulting in some cases in which the regression box with the highest classification score is not accurate. To address the lack of semantic information, an object tracking approach based on an ensemble semantic‐aware network and redetection (ESART) is proposed. Furthermore, a DarkNet53 network with transfer learning is used as our semantic‐aware model to adapt the detection task for extracting semantic information. In addition, a semantic tag redetection method to re‐evaluate the bounding box and overcome inaccurate scaling issues is proposed. Extensive experiments based on OTB2015, UAV123, UAV20L, and GOT‐10k show that our tracker is superior to other state‐of‐the‐art trackers. It is noteworthy that our semantic‐aware ensemble method can be embedded into any tracker for classification and regression task.

Over the past decade, organic–inorganic hybrid perovskite solar cells (PVSCs) have shown unprecedented growth in power conversion efficiency (PCE) from 3.8% to 25.7%. However, intrinsic thermal instability and lead toxicity are obstacles limiting its large–scale commercialization. Thus, all-inorganic CsSnI₃ perovskite has drawn remarkable interest owing to its nontoxicity, excellent thermal stability, low-cost fabrication, and spectacular photoelectric characteristics, including ideal bandgap range, long carrier lifetime, and large absorption coefficient. Many studies have shown that the device performances are closely related to the morphology and crystallinity of perovskite films. In this review, the physical properties of CsSnI₃ perovskite are summarized. Furthermore, this review primarily narrates the recent progress in optimizing the morphology by various strategies such as additive engineering, composition regulation, and deposition techniques, emphasizing their effects on grain sizes, film uniformity, grain boundary, and defect passivation.

The RAlX (R = Light rare earth; X = Ge, Si) compounds, as a family of magnetic Weyl semimetal, have recently attracted growing attention due to the tunability of Weyl nodes and its interactions with diverse magnetism by rare-earth atoms. Here, we report the magnetotransport evidence and electronic structure calculations on nontrivial band topology of SmAlSi, a new member of this family. At low temperatures, SmAlSi exhibits large non-saturated magnetoresistance (MR) (as large as ∼5500% at 2 K and 48 T) and distinct Shubnikov–de Haas (SdH) oscillations. The field dependent MRs at 2 K deviate from the semiclassical (μ ₀ H)² variation but follow the power-law relation MR ∝ (μ ₀ H) ^m with a crossover from m ∼ 1.52 at low fields (μ ₀ H< 15 T) to m ∼ 1 under high fields (μ ₀ H> 18 T), which is attributed to the existence of Weyl points and electron–hole compensated characteristics with high mobility. From the analysis of SdH oscillations, two fundamental frequencies originating from the Fermi surface pockets with non-trivial π Berry phases and small cyclotron mass can be identified, this feature is supported by the calculated electronic band structures with two Weyl pockets near the Fermi level. Our study establishes SmAlSi as a paradigm for researching the novel topological states of RAlX family.

Perovskite solar cells (PSCs) have received a great deal of attention in the science and technology field due to their outstanding power conversion efficiency (PCE), which increased rapidly from 3.9% to 25.5% in less than a decade, comparable to single crystal silicon solar cells. In the past ten years, much progress has been made, e.g. impressive ideas and advanced technologies have been proposed to enlarge PSC efficiency and stability. However, this outstanding progress has always been referred to as small-area (1 cm²) PSCs. Meanwhile, scaling up is an inevitable way for large-scale application of PSCs. Therefore, we firstly summarize the current achievements for high efficiency and stability large-area perovskite solar cells, including precursor composition, deposition, growth control, interface engineering, packaging technology, etc. Then we include a brief discussion and outlook for the future development of large-area PSCs in commercialization.

Majorana bound states are considered useful for realizing topological quantum computation since they obey the non-Abelian quantum statistics. Recent experiments have provided evidences for their existence in some superconducting systems, triggering significant interests from scientists in the field of condensed matter physics and related materials science. In this article, we briefly review the basic concepts and recent developments in the study of Majorana bound states. We first discuss about the origin of the nontrivial topology in superconducting systems within the Bogoliubov-de Gennes mean-field scheme. Then we show the construction of Majorana quasiparticle excitations from an electronic state, and the realization of non-Abelian statistics based on position exchanges of the Majorana bound states hosted in superconductivity vortices. Afterwards we talk about specific one-dimensional and two-dimensional topological superconductors, and propose possible experimental methods for detecting Majorana bound states and operating the Majorana qubits. In particular, a quantum device for Majorana braiding without moving vortices is introduced. Finally, perspectives of the study on Majorana bound states are provided.