The Clauser–Horne–Shimony–Holt (CHSH) game provides a captivating illustration of the advantages of quantum strategies over classical ones. In a recent study, a variant of the CHSH game leveraging a single qubit system, referred to as the CHSH$^*$ game, has been identified. We demonstrate that this mapping relationship between these two games remains effective even for a non-unitary gate. Here we delve into the breach of Tsirelson's bound in a non-Hermitian system, predicting changes in the upper and lower bounds of the player's winning probability when employing quantum strategies in a single dissipative qubit system. We experimentally explore the impact of the CHSH$^*$ game on the player's winning probability in a single trapped-ion dissipative system, demonstrating a violation of Tsirelson's bound under the influence of parity-time ($\mathcal{PT}$) symmetry. These results contribute to a deeper understanding of the influence of non-Hermitian systems on quantum games and the behavior of quantum systems under $\mathcal{PT}$ symmetry, which is crucial for designing more robust and efficient quantum protocols.

For a multi-component Maccari system with two spatial dimensions, nondegenerate one-soliton and two-soliton solutions are obtained with the bilinear method. It can be seen by drawing the spatial graphs of nondegenerate solitons that the real component of the system shows a cross-shaped structure, while the two solitons of the complex component show a multi-solitoff structure. At the same time, the asymptotic analysis of the interaction behavior of the two solitons is conducted, and it is found that under partially nondegenerate conditions, the real and complex components of the system experience elastic collision and inelastic collision, respectively.

The Cs$_{2}$NaInCl$_{6}$ double perovskite is one of the most promising lead-free perovskites due to its exceptional stability and straightforward synthesis. However, it faces challenges related to inefficient photoluminescence. Doping and high pressure are employed to tailor the optical properties of Cs$_{2}$NaInCl$_{6}$. Herein, Sb$^{3+}$ doped Cs$_{2}$NaInCl$_{6}$ (Sb$^{3+}$:Cs$_{2}$NaInCl$_{6})$ was synthesized and it exhibits blue emission with a photoluminescence quantum yield of up to 37.3%. Further, by employing pressure tuning, a blue stable emission under a very wide range from 2.7 GPa to 9.8 GPa is realized in Sb$^{3+}$:Cs$_{2}$NaInCl$_{6}$. Subsequently, the emission intensity of Sb$^{3+}$:Cs$_{2}$NaInCl$_{6}$ experiences a significant increase (3.3 times) at 19.0 GPa. It is revealed that the pressure-induced distinct emissions can be attributed to the carrier self-trapping and detrapping between Cs$_{2}$NaInCl$_{6}$ and Sb$^{3+}$. Notably, the lattice compression in the cubic phase inevitably modifies the band gap of Sb$^{3+}$:Cs$_{2}$NaInCl$_{6}$. Our findings provide valuable insights into effects of the high pressure in further boosting unique emission characteristics but also offer promising opportunities for development of doped double perovskites with enhanced optical functionalities.

We study superradiant phase transitions in a hybrid system of a two-dimensional Bose–Einstein condensate of atoms and two cavities arranged with a tilt angle. By adjusting the loss rate of cavities, we map out the phase diagram of steady states within a mean field framework. It is found that when the loss rates of the two cavities are different, superradiant transitions may not occur at the same time in the two cavities. A first-order phase transition is observed between the states with only one cavity in superradiance and both in superradiance. In the case that both cavities are superradiant, a net photon current is observed flowing from the cavity with small decay rate to the one with large decay rate. The photon current shows a non-monotonic dependence on the loss rate difference, owing to the competition of photon number difference and cavity field phase difference. Our findings can be realized and detected in experiments.

An implementation of high-precision time transfer over a 1839-km field fiber loop back link between two provincial capitals of China, Xi'an and Taiyuan, is reported. Time transfer stabilities of 6.5 ps at averaging time of 1 s and 4.6 ps at 40000 s were achieved. The uncertainty for the time transfer system was evaluated, showing a budget of 56.2 ps. These results stand for a significant milestone in achieving high-precision time transfer over a field fiber link spanning thousands of kilometers, signifying a record-breaking achievement for the real-field time transfer in both stability and distance, which paves the way for constructing the nationwide high-precision time service via fiber network.

Atomistic modeling is a widely employed theoretical method of computational materials science. It has found particular utility in the study of magnetic materials. Initially, magnetic empirical interatomic potentials or spin-polarized density functional theory (DFT) served as the primary models for describing interatomic interactions in atomistic simulations of magnetic systems. Furthermore, in recent years, a new class of interatomic potentials known as magnetic machine-learning interatomic potentials (magnetic MLIPs) has emerged. These MLIPs combine the computational efficiency, in terms of CPU time, of empirical potentials with the accuracy of DFT calculations. In this review, our focus lies on providing a comprehensive summary of the interatomic interaction models developed specifically for investigating magnetic materials. We also delve into the various problem classes to which these models can be applied. Finally, we offer insights into the future prospects of interatomic interaction model development for the exploration of magnetic materials.

We investigate high-pressure phase diagrams of Pr–N compounds by proposing five stable structures ($Pnma$-PrN, $I4/mmm$-PrN$_{2}$, $C2/m$-PrN$_{3}$, $P\bar{1}$-PrN$_{4}$, and $R3$-PrN$_{8})$ and two metastable structures ($P\bar{1}$-PrN$_{6}$ and $P\bar{1}$-PrN$_{10}$). The $P\bar{1}$-PrN$_{6}$ with the N$_{14}$-ring layer and $R3$-PrN$_{8}$ with the N$_{18}$-ring layer can be quenched to ambient conditions. For the $P\bar{1}$-PrN$_{10}$, the N$_{22}$-ring layer structure transfers into infinite chains with the pressure quenched to ambient pressure. Remarkably, a novel polynitrogen $hR8$-N designed by the excision of Pr atoms from $R3$-PrN$_{8}$ is obtained and can be quenched to ambient conditions. The N-rich structures of $P\bar{1}$-PrN$_{6}$, $R3$-PrN$_{8}$, c-PrN$_{10}$ and the solid pure nitrogen structure exhibit outstanding properties of energy density and explosive performance.

Hall effects have been the central paradigms in modern physics, materials science and practical applications, and have led to many exciting breakthroughs, including the discovery of topological Chern invariants and the revolution of metrological resistance standard. To date, the Hall effects have mainly focused on a single degree of freedom (DoF), and most of them require the breaking of spatial-inversion and/or time-reversal symmetries. Here we demonstrate a new type of Hall effect, i.e., layer-valley Hall effect, based on a combined layer-valley DoF characterized by the product of layer and valley indices. The layer-valley Hall effect has a quantum origin arising from the layer-valley contrasting Berry curvature, and can occur in nonmagnetic centrosymmetric crystals with both spatial-inversion and time-reversal symmetries, transcending the symmetry constraints of single DoF Hall effect based on the constituent layer or valley index. Moreover, the layer-valley Hall effect is highly tunable and shows a W-shaped pattern in response to the out-of-plane electric fields. Additionally, we discuss the potential detection approaches and material-specific design principles of layer-valley Hall effect. Our results demonstrate novel Hall physics and open up exotic paradigms for new research direction of layer-valleytronics that exploits the quantum nature of the coupled layer-valley DoF.

Two-dimensional (2D) topological materials have recently garnered significant interest due to their profound physical properties and promising applications for future quantum nanoelectronics. Achieving various topological states within one type of materials is, however, seldom reported. Based on first-principles calculations and tight-binding models, we investigate topological electronic states in a novel family of 2D halogenated tetragonal stanene (T-SnX, X = F, Cl, Br, I). All the four monolayers are found to be unusual topological nodal-line semimetals (NLSs), protected by a glide mirror symmetry. When spin-orbit coupling (SOC) is turned on, T-SnF and T-SnCl are still ascertained as topological NLSs due to the remaining band inversion, primarily composed of Sn $p_{xy}$ orbitals, while T-SnBr and T-SnI become quantum spin Hall insulators. The phase transition is ascribed to moving up in energy of Sn $s$ orbitals and increasing of SOC strengths. The topology origin in the materials is uniformly rationalized through elementary band representations. The robust and diverse topological states found in the 2D T-SnX monolayers position them as an excellent material platform for development of innovative topological electronics.

Antiferromagnetic spin fluctuation is regarded as the leading driving force for electron pairing in high-$T_{\rm c}$ superconductors. In iron-based superconductors, spin excitations at low energy range, especially the spin-resonance mode at $E_{\rm R} \sim5k_{\rm B}T_{\rm c}$, are important for understanding the superconductivity. Here, we use inelastic neutron scattering (INS) to investigate the symmetry and in-plane wave-vector dependence of low-energy spin excitations in uniaxial-strain detwinned FeSe. The low-energy spin excitations ($E < 10$ meV) appear mainly at ${\boldsymbol Q} = (\pm 1,\, 0)$ in the superconducting state ($T\lesssim9$ K) and the nematic state ($T\lesssim90$ K), confirming the constant $C_2$ rotational symmetry and ruling out the $C_4$ mode at $E\approx3$ meV reported in a prior INS study. Moreover, our results reveal an isotropic spin resonance in the superconducting state, which is consistent with the $s^{\pm}$ wave pairing symmetry. At slightly higher energy, low-energy spin excitations become highly anisotropic. The full width at half maximum of spin excitations is elongated along the transverse direction. The $Q$-space isotropic spin resonance and highly anisotropic low-energy spin excitations could arise from $d_{yz}$ intra-orbital selective Fermi surface nesting between the hole pocket around $\varGamma$ point and the electron pockets centered at $M_{\rm X}$ point.

Controlling the size and distribution of potential barriers within a medium of interacting particles can unveil unique collective behaviors and innovative functionalities. We introduce a unique superconducting hybrid device using a novel artificial spin ice structure composed of asymmetric nanomagnets. This structure forms a distinctive superconducting pinning potential that steers unconventional motion of superconducting vortices, thereby inducing a magnetic nonreciprocal effect, in contrast to the electric nonreciprocal effect commonly observed in superconducting diodes. Furthermore, the polarity of the magnetic nonreciprocity is in situ reversible through the tunable magnetic patterns of artificial spin ice. Our findings demonstrate that artificial spin ice not only precisely modulates superconducting characteristics but also opens the door to novel functionalities, offering a groundbreaking paradigm for superconducting electronics.

Novel magnetic materials with non-trivial magnetic structures have led to exotic magnetic transport properties and significantly promoted the development of spintronics in recent years. Among them is the Cr$_{x}$Te$_{y}$ family, the magnetism of which can persist above room temperature, thus providing an ideal system for potential spintronic applications. Here we report the synthesis of a new compound, Cr$_{0.82}$Te, which demonstrates a record-high topological Hall effect at room temperature in this family. Cr$_{0.82}$Te displays soft ferromagnetism below the Curie temperature of 340 K. The magnetic measurement shows an obvious magneto-crystalline anisotropy with the easy axis located in the $ab$ plane. The anomalous Hall effect can be well explained by a dominating skew scattering mechanism. Intriguing, after removing the normal Hall effect and anomalous Hall effect, a topological Hall effect can be observed up to 300 K and reaches up to 1.14 $µ\Omega\cdot$cm at 10 K, which is superior to most topological magnetic structural materials. This giant topological Hall effect possibly originates from the noncoplanar spin configuration during the spin flop process. Our work extends a new Cr$_{x}$Te$_{y}$ system with topological non-trivial magnetic structure and broad prospects for spintronics applications in the future.

Graphene (Gr) with widely acclaimed characteristics, such as exceptionally long spin diffusion length at room temperature, provides an outstanding platform for spintronics. However, its inherent weak spin–orbit coupling (SOC) has limited its efficiency for generating the spin currents in order to control the magnetization switching process for applications in spintronics memories. Following the theoretical prediction on the enhancement of SOC in Gr by heavy atoms adsorption, here we experimentally observe a sizeable spin–orbit torques (SOTs) in Gr by the decoration of its surface with Pt adatoms in Gr/Pt($t_{\rm Pt} $)/FeNi trilayers with the optimal damping-like SOT efficiency around 0.55 by 0.6-nm-thick Pt layer adsorption. The value is nearly four times larger than that of the Pt/FeNi sample without Gr and nearly twice the value of the Gr/FeNi sample without Pt adsorption. The efficiency of the enhanced SOT in Gr by Pt adatoms is also demonstrated by the field-free SOT magnetization switching process with a relatively low critical current density around 5.4 MA/cm$^2$ in Gr/Pt/FeNi trilayers with the in-plane magnetic anisotropy. These findings pave the way for Gr spintronics applications, offering solutions for future low power consumption memories.

The discovery of ferromagnetic two-dimensional (2D) van der Waals (vdWs) materials provides an opportunity to explore intriguing physics and to develop innovative spin electronic devices. However, the main challenge for practical applications of vdWs ferromagnetic crystals lies in the weak intrinsic ferromagnetism and small perpendicular magnetic anisotropy (PMA) above room temperature. Here, we report the intrinsic vdWs ferromagnetic crystal Fe$_{3}$GaTe$_{2}$, synthesized by the self-flux method, exhibiting a Curie temperature ($T_{\rm C}$) of 370 K, a high saturation magnetization of 33.47 emu/g, and a large PMA energy density of approximately $4.17 \times 10^{5}$ J/m$^{3}$. Furthermore, the magneto-optical effect is systematically investigated in Fe$_{3}$GaTe$_{2}$. The doubly degenerate $E_{\rm 2g} (\varGamma)$ mode reverses the helicity of incident photons, indicating the existence of pseudoangular-momentum (PAM) and chirality. Meanwhile, the non-degenerate non-chiral $A_{\rm 1g}(\varGamma)$ phonon exhibits a significant magneto-Raman effect under an external out-of-plane magnetic field. These results lay the groundwork for studying phonon chirality and magneto-optical phenomena in 2D magnetic materials, providing the feasibility for further fundamental research and applications in spintronic devices.

In the era of Internet of Things (IoTs), an energy-efficient ultraviolet (UV) photodetector (PD) is highly desirable considering the massive usage scenarios such as environmental sterilization, fire alarm and corona discharge monitoring. So far, common self-powered UV PDs are mainly based on metal-semiconductor hetero-structures or p–n heterojunctions, where the limited intrinsic built-in electric field restricts further enhancement of the photoresponsivity. In this work, an extremely low-voltage field-effect UV PD is proposed using a gate-drain shorted amorphous IGZO (a-IGZO) thin film transistor (TFT) architecture. A combined investigation of the experimental measurements and technology computer-aided design (TCAD) simulations suggests that the reverse current ($I_{\rm R}$) of field-effect diode (FED) is highly related with the threshold voltage ($V_{\rm th}$) of the parental TFT, implying an enhancement-mode TFT is preferable to fabricate the field-effect UV PD with low dark current. Driven by a low bias of $-0.1$ V, decent UV response has been realized including large UV/visible ($R_{300}/R_{550}$) rejection ratio ($1.9\times 10^{3}$), low dark current ($1.15\times 10^{-12}$ A) as well as high photo-to-dark current ratio (PDCR, $\sim$ $10^{3}$) and responsivity (1.89 A/W). This field-effect photodiode provides a new platform to construct UV PDs with well-balanced photoresponse performance at a low bias, which is attractive for designs of large-scale smart sensor networks with high energy efficiency.