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Muography is a rapidly developing and non-destructive tomographic technology that uses cosmic ray muons. Due to the natural presence and deeper penetration of cosmic ray muons, scientists have performed various pioneer studies in fields, such as customs security, the internal imaging of volcanoes, scientific archaeology, and others. With unique advantages, muography has gained increasing attention from archaeologists as a novel and innovative tool to investigate large-scale archaeological sites. This approach may be especially helpful for identifying endangered cultural relics and monuments. In the work, we employ a compact, rugged, and portable muon imaging system, CORMIS (COsmic Ray Muon Imaging System), deployed at up to six measurement locations to perform a case study of three-dimensional muography in Xi'an city, China. Cultural cities, such as Xi'an, have long histories and could benefit from innovative techniques used to investigate, conserve, and protect large historical sites. In this paper, we present in detail a high resolution survey on a rampart of a Xi'an defensive wall in demand of urgent protection. The survey data are carefully processed with advanced statistical methods newly introduced in muography, and the results indicate density anomalies inside the rampart with unprecedented levels of precision. The density anomalies are potential safety hazards and need to be eliminated as soon as possible. The successful implementation of this survey significantly encourages more engagement on the tangible application of high-precision 3D muography in archaeological investigations and protection projects around the world. [ABSTRACT FROM AUTHOR]

This systematic study on the intrinsic spin Hall conductivity (SHC) of BiTeI aims to explore the role of hydrostatic pressure in controlling the topological properties and SHC. It was found that the sign of transverse spin Hall conductivity tensors σ x y z , σ x z y , and σ z x y in BiTeI is reversed due to the topological transition under hydrostatic pressure. The change in sign originates from the variation in spin Berry curvature near A in the Brillouin zone, which is caused by Te-p and I-p orbital hybridization induced by the interplay coupling under hydrostatic pressure in BiTeI. Thus, SHC could be effectively tuned by changing the hydrostatic pressure. These results not only allow us to establish a fundamental understanding of SHC in BiTeI depending on the pressure but also provide guidelines for applying BiTeI in next-generation spintronic devices. [ABSTRACT FROM AUTHOR]

Two-dimensional ferromagnetic topological semi-metals have attracted much interest owing to their fascinating spintronic applications. Using first-principles calculations, we propose a stable transition metal nitrogen halide compound, namely, VNI monolayer, to display intrinsic ferromagnetism with high Curie temperature TC (∼510 K) and strong out-of-plane magnetism. It is found to be a topological Weyl nodal line material, which can be fully spin-polarized by controlling the on-site Coulomb interaction. Its nodal line can be destroyed by orienting the magnetization axis. Additionally, biaxial strain enables efficient tuning of the magnetic properties by switching the easy magnetic axis from an out-of-plane to in-plane direction with an enhanced TC to 540 K. These results highlight the great application potential of a VNI monolayer in low-dimensional topological magnets. [ABSTRACT FROM AUTHOR]

Topological semimetals represent one of the most interesting classes of materials that continue to attract worldwide interest. Here, we report magnetotransport properties of MPn2-type (M=Nb, Ta; Pn=P, As, Sb) NbSb2 single-crystal semimetals with a centrosymmetric C12/m1 space group, paramagnetic ground state, and non-saturation parabolic-like magnetoresistance. The NbSb2 crystals show metallic conductivity down to 2K and undergo a metal-to-insulator-like transition under a magnetic field B (B ≥ 4 T) and exhibit a resistivity plateau in the lowtemperature region (T ≤ 10K), where the value of resistivity strongly depends on the magnitude and direction of the magnetic field. Upon sweeping the magnetic field from 0 to 14.5 T in the transverse configuration at T=1.5K, the NbSb2 crystal shows a large positive magnetoresistance (4.2 x 10³% at B=14.5 T) with Shubnikov-de Haas (SdH) oscillation. Hall measurements reveal that both the carrier compensation between electrons and holes and the high mobility and large mean free path of carriers contribute to the large magnetoresistance. Fast Fourier transform analyses of angle-resolved SdH oscillation indicate that the Fermi surface of the NbSb2 crystal is quasi-two-dimensional with three-dimensional components. These findings, together with the theoretically calculated electronic band structure obtained within the framework of density functional theory, suggest that NbSb2 is a good candidate compensated semimetal for further theoretical and experimental investigation of this family of materials. [ABSTRACT FROM AUTHOR]