Explore the vast range of titles available.

Fundamental physical properties, such as phase transitions, electronic structures, and spin excitations, in all magnetic ordered materials, were ultimately believed to rely on the symmetry theory of magnetic space groups. Recently, it has come to light that a more comprehensive group, known as the spin space group (SSG), which combines separate spin and spatial operations, is necessary to fully characterize the geometry and underlying properties of magnetic ordered materials. However, the basic theory of SSG has seldom been developed. In this work, we present a systematic study of the enumeration and the representation theory of the SSG. Starting from the 230 crystallographic space groups and finite translation groups with a maximum order of eight, we establish an extensive collection of over 100 000 SSGs under a four-index nomenclature as well as international notation. We then identify inequivalent SSGs specifically applicable to collinear, coplanar, and noncoplanar magnetic configurations. To facilitate the identification of the SSG, we develop an online program that can determine the SSG symmetries of any magnetic ordered crystal. Moreover, we derive the irreducible corepresentations of the little group in momentum space within the SSG framework. Finally, we illustrate the SSG symmetries and physical effects beyond the framework of magnetic space groups through several representative material examples, including a candidate altermagnet RuO 2 , spiral spin polarization in the coplanar antiferromagnet CeAuAl 3 , and geometric Hall effect in the noncoplanar antiferromagnet CoNb 3 S 6 . Our work advances the field of group theory in describing magnetic ordered materials, opening up avenues for deeper comprehension and further exploration of emergent phenomena in magnetic materials.

Spatial, momentum and energy separation of electronic spins in condensed-matter systems guides the development of new devices in which spin-polarized current is generated and manipulated 1 – 3 . Recent attention on a set of previously overlooked symmetry operations in magnetic materials 4 leads to the emergence of a new type of spin splitting, enabling giant and momentum-dependent spin polarization of energy bands on selected antiferromagnets 5 – 10 . Despite the ever-growing theoretical predictions, the direct spectroscopic proof of such spin splitting is still lacking. Here we provide solid spectroscopic and computational evidence for the existence of such materials. In the noncoplanar antiferromagnet manganese ditelluride (MnTe 2 ), the in-plane components of spin are found to be antisymmetric about the high-symmetry planes of the Brillouin zone, comprising a plaid-like spin texture in the antiferromagnetic (AFM) ground state. Such an unconventional spin pattern, further found to diminish at the high-temperature paramagnetic state, originates from the intrinsic AFM order instead of spin–orbit coupling (SOC). Our finding demonstrates a new type of quadratic spin texture induced by time-reversal breaking, placing AFM spintronics on a firm basis and paving the way for studying exotic quantum phenomena in related materials. Examining the in-plane spin components of the noncoplanar antiferromagnet manganese ditelluride provides spectroscopic and computational evidence of materials with a new type of plaid-like spin splitting in the antiferromagnetic ground state.

Magnetic topological insulators (TI) provide an important material platform to explore quantum phenomena such as quantized anomalous Hall effect and Majorana modes, etc. Their successful material realization is thus essential for our fundamental understanding and potential technical revolutions. By realizing a bulk van der Waals material MnBi 4 Te 7 with alternating septuple [MnBi 2 Te 4 ] and quintuple [Bi 2 Te 3 ] layers, we show that it is ferromagnetic in plane but antiferromagnetic along the c axis with an out-of-plane saturation field of ~0.22 T at 2 K. Our angle-resolved photoemission spectroscopy measurements and first-principles calculations further demonstrate that MnBi 4 Te 7 is a Z 2 antiferromagnetic TI with two types of surface states associated with the [MnBi 2 Te 4 ] or [Bi 2 Te 3 ] termination, respectively. Additionally, its superlattice nature may make various heterostructures of [MnBi 2 Te 4 ] and [Bi 2 Te 3 ] layers possible by exfoliation. Therefore, the low saturation field and the superlattice nature of MnBi 4 Te 7 make it an ideal system to investigate rich emergent phenomena. Emergent quantum phenomena such as quantized anomalous Hall effect may be realized in magnetic topological materials. Here, Hu et al. discovered an intrinsic natural heterostructural Z 2 antiferromagnetic topological insulator MnBi 4 Te 7 with low out-of-plane saturation fields.

The triboelectric nanogenerator (TENG) and its application as a sensor is a popular research subject. There is demand for self-powered, flexible sensors with high sensitivity and high power-output for the next generation of consumer electronics. In this study, a 300 mm × 300 mm carbon nanotube (CNT)-doped porous PDMS film was successfully fabricated wherein the CNT influenced the micropore structure. A self-powered TENG tactile sensor was established according to triboelectric theory. The CNT-doped porous TENG showed a voltage output seven times higher than undoped porous TENG and 16 times higher than TENG with pure PDMS, respectively. The TENG successfully acquired human motion signals, breath signals, and heartbeat signals during a sleep monitoring experiment. The results presented here may provide an effective approach for fabricating large-scale and low-cost flexible TENG sensors.

Spin textures, i.e., the distribution of spin polarization vectors in reciprocal space, exhibit diverse patterns determined by symmetry constraints, resulting in a variety of spintronic phenomena. Here, we propose a universal theory to comprehensively describe the nature of spin textures by incorporating three symmetry flavors of reciprocal wavevector, atomic orbital, and atomic site. Such an approach enables us to establish a complete classification of spin textures constrained by the little co-group and predict some exotic spin texture types, such as Zeeman-type spin splitting in antiferromagnets and quadratic spin texture. To illustrate the influence of atomic orbitals and sites on spin textures, we predict orbital-dependent spin texture and anisotropic spin-momentum-site locking effects, and corresponding material candidates validated through first-principles calculations. The comprehensive classification and the predicted new spin textures in realistic materials are expected to trigger future spin-based functionalities in electronics.

A novel method for Li-ion battery state of charge (SOC) estimation based on a super-twisting sliding mode observer (STSMO) is proposed in this paper. To design the STSMO, the state equation of a second-order RC equivalent circuit model (SRCECM) is derived to represent the dynamic behaviors of the Li-ion battery, and the model parameters are determined by the pulse current discharge approach. The convergence of the STSMO is proven by Lyapunov stability theory. The experiments under three different discharge profiles are conducted on the Li-ion battery. Through comparisons with a conventional sliding mode observer (CSMO) and adaptive extended Kalman filter (AEKF), the superiority of the proposed observer for SOC estimation is validated.

The century-long development of surface sciences has witnessed the discoveries of a variety of quantum states. In the recently proposed “obstructed atomic insulators”, symmetric charges are pinned at virtual sites where no real atoms reside. The cleavage through these sites could lead to a set of obstructed surface states with partial electronic occupation. Here, utilizing scanning tunneling microscopy, angle-resolved photoemission spectroscopy and first-principles calculations, we observe spectroscopic signature of obstructed surface states in SrIn 2 P 2 . We find that a pair of surface states that are originated from the pristine obstructed surface states split in energy by a unique surface reconstruction. The upper branch is marked with a striking differential conductance peak followed by negative differential conductance, signaling its localized nature, while the lower branch is found to be highly dispersive. This pair of surface states is in consistency with our calculational results. Our finding not only demonstrates a surface quantum state induced by a new type of bulk-boundary correspondence, but also provides a platform for exploring efficient catalysts and related surface engineering. The authors observe spectroscopic signature of obstructed surface states on the (0001) plane of SrIn 2 P 2 . Due to structural reconstruction, the surface state undergoes an adiabatic evolution and split into two branches, the upper of which being spatially localized with unusual negative differential conductance.

Excluding rough areas with surface rocks and craters is critical for the safety of landing missions, such as China’s Chang’e-7 mission, in the permanently shadowed region (PSR) of the lunar south pole. Binned digital elevation model (DEM) data can describe the undulating surface, but the DEM data can hardly detect surface rocks because of median-averaging. High-resolution images from a synthetic aperture radar (SAR) can be used to map discrete rocks and small craters according to their strong backscattering. This study utilizes the You Only Look Once version 7 (YOLOv7) tool to detect varying-sized craters in SAR images. It also employs the Markov random field (MRF) algorithm to identify surface rocks, which are usually difficult to detect in DEM data. The results are validated by optical images and DEM data in non-PSR. With the assistance of the DEM data, regions with slopes larger than 10° are excluded. YOLOv7 and MRF are applied to detect craters and rocky surfaces and exclude regions with steep slopes in the PSRs of craters Shoemaker, Slater, and Shackleton, respectively. This study proves SAR images are feasible in the selection of landing sites in the PSRs for future missions.

Antiferromagnets have attracted widespread interest due to the advantages of no stray fields and ultrafast switching dynamics, promising for next‐generation high‐speed, high‐density memories. However, over a long period, the effective detection of antiferromagnetic (AFM) orders remained being one of the greatest challenges of its application in magnetic random access memories (MRAM) because of its zero net magnetization. Recently, the preliminary demonstration of the tunneling magnetoresistance ratio(TMR) in antiferromagnetic tunnel junctions (AFMTJ) offered a feasible solution. Here, a Mn3SnN/SrTiO3/Mn3SnN non‐collinear AFMTJ is designed and its transport properties are predicted by ab initio quantum transport simulations. Due to the momentum matching between the spin‐polarized Fermi surface of the Mn3SnN electrode and the low‐decay‐rate evanescent states of the SrTiO3 barrier, a remarkable TMR ≈1500% is generated, corresponding to a large device read margin, resulting in higher storage density. In addition, changing the relative orientation of two Mn3SnN magnetic orders leads to four non‐volatile resistance states with a low resistance area (RA) of only 0.07–1.25 Ω•µm2 and three multi‐state TMR of ≈500, 1000, and 1500%, suitable for high‐energy‐efficiency multiple‐state memory application. Our work provides a promising device structure for future nonvolatile high‐speed, high‐density, and multiple‐state AFM memories. A non‐collinear Mn3SnN/SrTiO3/Mn3SnN (001) AFMTJ is proposed with a theoretical TMR exceeding 1500%, enabled by optimal momentum (k)‐space matching between Mn3SnN's spin‐polarized Fermi surface (pk|| ${p}_{{\\bm{k}}_{\\mathbf{|}\\mathbf{|}}}$ ) and the low‐decay‐rate (κk|| ${\\kappa}_{{\\bm{k}}_{\\mathbf{|}\\mathbf{|}}}$ ) of the SrTiO3 barrier. The eight degenerate AFM states of Mn3SnN enable multistate resistance and thus three distinct TMR values, offering a promising platform for future functional antiferromagnetic MRAM.

Fostering human–wildlife coexistence necessitates a thorough and nuanced grasp of local attitudes toward wildlife. Attitudes can vary substantially based on the sociodemographic backgrounds of individuals within a society. This study examines Tibetan attitudes toward large carnivores, emphasizing the importance of contextualization in discerning the effects of sociodemographic factors on attitudes. We began by analyzing existing research on Tibetan attitudes toward wildlife in China, identifying previously studied sociodemographic variables. We then executed an online survey to evaluate the affective, behavioral, cognitive, and overall attitudes of ethnic Tibetans in China toward snow leopards (Panthera uncia), gray wolves (Canis lupus), and brown bears (Ursus arctos). Our findings show that while factors such as gender, age, religious identity, and level of education shape these attitudes, their influence differs depending on the specific attitude component and the target animal under examination. Therefore, making broad generalizations about sociodemographic differences in attitudes can be misleading. It is imperative for attitude research to clearly define the attitude component (what type of attitude), object (attitude toward what), and circumstance (attitude in which situation) being studied. Conducting ethnographic fieldwork in collaboration with local cultural experts can deepen our understanding of local perspectives and the ways sociodemographic factors influence attitudes. Such insights are pivotal for developing conservation strategies attuned to local sociocultural contexts. This paper presents a case study of ethnic Tibetan attitudes toward large carnivores to highlight the importance of contextualization for understanding sociodemographic differences in attitudes. We suggest that attitude research should clearly define the attitude component (what type of attitude), object (attitude toward what), and circumstance (attitude in which situation) being studied.