Evidence of Ferroelectric Distortions in Topological Crystalline Insulators via Transverse Thermoelectric Measurements.

The transverse thermoelectric (Nernst) effect is a powerful probe for studying the electronic and structural properties of materials. In this study, we employ transverse thermoelectric measurements to investigate the ferroelectric distortion in the topological crystalline insulator (TCI) PbSnTe, a compound derived from PbTe and SnTe, known for their exceptional thermoelectric performance and distinct ferroelectric properties. By leveraging Nernst measurements, we provide direct evidence of ferroelectric distortion in this TCI, corroborated by Shubnikov-de Haas quantum oscillations that confirm the presence of two topologically nontrivial Fermi pockets.

Spin-to-Charge Conversion in Orthorhombic RhSi Crystalline Thin Films.

The rise of nonmagnetic topological semimetals, which provide a promising platform for observing and controlling various spin-orbit effects, has led to significant advancements in the field of topological spintronics. RhSi exists in two distinct polymorphs: cubic and orthorhombic crystal structures. The noncentrosymmetric B20 cubic structure has been extensively studied in the bulk for hosting unconventional multifold Fermions.

Direct control of electron spin at an intrinsically chiral surface for highly efficient oxygen reduction reaction.

The oxygen reduction reaction (ORR) in acidic media suffers from sluggish kinetics, primarily due to the spin-dependent electron transfer involved. The direct generation of spin-polarized electrons at catalytic surfaces remains elusive, and the underlying mechanisms are still controversial due to the lack of intrinsically chiral catalysts. To address this challenge, we investigate topological homochiral PdGa (TH PdGa) crystals with intrinsically chiral catalytic surfaces for ORR.

Controllable orbital angular momentum monopoles in chiral topological semimetals.

The emerging field of orbitronics aims to generate and control orbital angular momentum for information processing. Chiral crystals are promising orbitronic materials because they have been predicted to host monopole-like orbital textures, where the orbital angular momentum aligns isotropically with the electron's crystal momentum. However, such monopoles have not yet been directly observed in chiral crystals.

Designing giant Hall response in layered topological semimetals.

Noncoplanar magnets are excellent candidates for spintronics. However, such materials are difficult to find, and even more so to intentionally design. Here, we report a chemical design strategy that allows us to find a series of noncoplanar magnets-LnSn (Ln = Dy, Tb)-by targeting layered materials that have decoupled magnetic sublattices with dissimilar single-ion anisotropies and combining those with a square-net topological semimetal sublattice.

Axion topology in photonic crystal domain walls.

Axion insulators are 3D magnetic topological insulators supporting hinge states and quantized magnetoelectric effects, recently proposed for detecting dark-matter axionic particles via their axionic excitations. Beyond theoretical interest, obtaining a photonic counterpart of axion insulators offers potential for advancing magnetically-tunable photonic devices and axion haloscopes based on axion-photon conversion. This work proposes an axionic 3D phase within a photonic setup.

Weyl spin-momentum locking in a chiral topological semimetal.

Spin-orbit coupling in noncentrosymmetric crystals leads to spin-momentum locking - a directional relationship between an electron's spin angular momentum and its linear momentum. Isotropic orthogonal Rashba spin-momentum locking has been studied for decades, while its counterpart, isotropic parallel Weyl spin-momentum locking has remained elusive in experiments. Theory predicts that Weyl spin-momentum locking can only be realized in structurally chiral cubic crystals in the vicinity of Kramers-Weyl or multifold fermions.

Monopole-like orbital-momentum locking and the induced orbital transport in topological chiral semimetals.

The interplay between chirality and topology nurtures many exotic electronic properties. For instance, topological chiral semimetals display multifold chiral fermions that manifest nontrivial topological charge and spin texture. They are an ideal playground for exploring chirality-driven exotic physical phenomena.

Atomically Sharp Internal Interface in a Chiral Weyl Semimetal Nanowire.

Internal interfaces in Weyl semimetals (WSMs) are predicted to host distinct topological features that are different from the commonly studied external interfaces (crystal-to-vacuum boundaries). However, the lack of atomically sharp and crystallographically oriented internal interfaces in WSMs makes it difficult to experimentally investigate topological states buried inside the material. Here, we study a unique internal interface known as twin boundary in chemically synthesized single-crystal nanowires (NWs) of CoSi, a chiral WSM of space group 23 (No.

Cubic 3D Chern photonic insulators with orientable large Chern vectors.

Time Reversal Symmetry (TRS) broken topological phases provide gapless surface states protected by topology, regardless of additional internal symmetries, spin or valley degrees of freedom. Despite the numerous demonstrations of 2D topological phases, few examples of 3D topological systems with TRS breaking exist. In this article, we devise a general strategy to design 3D Chern insulating (3D CI) cubic photonic crystals in a weakly TRS broken environment with orientable and arbitrarily large Chern vectors.

Weyl fermions, Fermi arcs, and minority-spin carriers in ferromagnetic CoS.

Magnetic Weyl semimetals are a newly discovered class of topological materials that may serve as a platform for exotic phenomena, such as axion insulators or the quantum anomalous Hall effect. Here, we use angle-resolved photoelectron spectroscopy and ab initio calculations to discover Weyl cones in CoS, a ferromagnet with pyrite structure that has been long studied as a candidate for half-metallicity, which makes it an attractive material for spintronic devices. We directly observe the topological Fermi arc surface states that link the Weyl nodes, which will influence the performance of CoS as a spin injector by modifying its spin polarization at interfaces.

The Subchalcogenides IrInQ (Q = S, Se, Te): Dirac Semimetal Candidates with Re-entrant Structural Modulation.

Subchalcogenides are uncommon compounds where the metal atoms are in unusually low formal oxidation states. They bridge the gap between intermetallics and semiconductors and can have unexpected structures and properties because of the exotic nature of their chemical bonding as they contain both metal-metal and metal-main group (e.g.

A New Three-Dimensional Subsulfide IrInS with Dirac Semimetal Behavior.

Dirac and Weyl semimetals host exotic quasiparticles with unconventional transport properties, such as high magnetoresistance and carrier mobility. Recent years have witnessed a huge number of newly predicted topological semimetals from existing databases; however, experimental verification often lags behind such predictions. Common reasons are synthetic difficulties or the stability of predicted phases.

Large Multidirectional Spin-to-Charge Conversion in Low-Symmetry Semimetal MoTe at Room Temperature.

Efficient and versatile spin-to-charge current conversion is crucial for the development of spintronic applications, which strongly rely on the ability to electrically generate and detect spin currents. In this context, the spin Hall effect has been widely studied in heavy metals with strong spin-orbit coupling. While the high crystal symmetry in these materials limits the conversion to the orthogonal configuration, unusual configurations are expected in low-symmetry transition-metal dichalcogenide semimetals, which could add flexibility to the electrical injection and detection of pure spin currents.