New Layered Fluorosulfide SrFBiS₂

We have synthesized a new layered BiS₂-based compound, SrFBiS₂. This compound has a similar structure to LaOBiS₂. It is built up by stacking up SrF layers and NaCl-type BiS₂ layers alternatively along the <i>c</i> axis. Electric transport measurement indicates that SrFBiS₂ is a semiconductor. Thermal transport measurement shows that SrFBiS₂ has a small thermal conductivity and large Seebeck coefficient. First principle calculations are in agreement with experimental results and show that SrFBiS₂ is very similar to LaOBiS₂, which becomes a superconductor with F doping. Therefore, SrFBiS₂ may be a parent compound of new superconductors

Layered Compounds BaM₂Ge₄Ch₆ (M = Rh, Ir and Ch = S, Se) with Pyrite-Type Building Blocks and Ge–Ch Heteromolecule-Like Anions

The structures and chemical features of layered compounds BaM₂Ge₄Ch₆ (M = Rh, Ir; Ch = S, Se) synthesized by high-pressure and high-temperature methods have been systematically studied. These compounds crystallize in an orthorhombic phase with space group <i>Pbca</i> (No. 61). These compounds have the remarkable structural feature of M–Ge–Ch pyrite-type building units, stacking with Ba–Ch layers alternatively along the <i>c</i> axis. It is very rare and novel that pyrite-type subunits are the building blocks in layered compounds. Theoretical calculations and experimental results indicate that there are strongly polarized covalent bonds between Ge and Ch atoms, forming heteromolecule-like anions in these compounds. Moreover, Ge atoms in this structure exhibit an unusual valence state (∼+1) due to the tetrahedral coordination environment of Ge atoms along with M and Ch atoms simultaneously

Layered Compounds BaM₂Ge₄Ch₆ (M = Rh, Ir and Ch = S, Se) with Pyrite-Type Building Blocks and Ge–Ch Heteromolecule-Like Anions

The structures and chemical features of layered compounds BaM₂Ge₄Ch₆ (M = Rh, Ir; Ch = S, Se) synthesized by high-pressure and high-temperature methods have been systematically studied. These compounds crystallize in an orthorhombic phase with space group <i>Pbca</i> (No. 61). These compounds have the remarkable structural feature of M–Ge–Ch pyrite-type building units, stacking with Ba–Ch layers alternatively along the <i>c</i> axis. It is very rare and novel that pyrite-type subunits are the building blocks in layered compounds. Theoretical calculations and experimental results indicate that there are strongly polarized covalent bonds between Ge and Ch atoms, forming heteromolecule-like anions in these compounds. Moreover, Ge atoms in this structure exhibit an unusual valence state (∼+1) due to the tetrahedral coordination environment of Ge atoms along with M and Ch atoms simultaneously

Superconductivity in Alkaline Earth Metal-Filled Skutterudites Ba_<i>x</i>Ir₄X₁₂ (X = As, P)

We report superconductive iridium pnictides Ba_<i>x</i>Ir₄X₁₂ (X = As and P) with a filled skutterudite structure, demonstrating that Ba filling dramatically alters their electronic properties and induces a nonmetal-to-metal transition with increasing the Ba content <i>x</i>. The highest superconducting transition temperatures are 4.8 and 5.6 K observed for Ba_<i>x</i>Ir₄As₁₂ and Ba_<i>x</i>Ir₄P₁₂, respectively. The superconductivity in Ba_<i>x</i>Ir₄X₁₂ can be classified into the Bardeen–Cooper–Schrieffer type with intermediate coupling

One Million Percent Tunnel Magnetoresistance in a Magnetic van der Waals Heterostructure

We report the observation of a very large negative magnetoresistance effect in a van der Waals tunnel junction incorporating a thin magnetic semiconductor, CrI₃, as the active layer. At constant voltage bias, current increases by nearly one million percent upon application of a 2 T field. The effect arises from a change between antiparallel to parallel alignment of spins across the different CrI₃ layers. Our results elucidate the nature of the magnetic state in ultrathin CrI₃ and present new opportunities for spintronics based on two-dimensional materials

Narrow Bandgap in β‑BaZn₂As₂ and Its Chemical Origins

β-BaZn₂As₂ is known to be a p-type semiconductor with the layered crystal structure similar to that of LaZnAsO, leading to the expectation that β-BaZn₂As₂ and LaZnAsO have similar bandgaps; however, the bandgap of β-BaZn₂As₂ (previously reported value ∼0.2 eV) is 1 order of magnitude smaller than that of LaZnAsO (1.5 eV). In this paper, the reliable bandgap value of β-BaZn₂As₂ is determined to be 0.23 eV from the intrinsic region of the temperature dependence of electrical conductivity. The origins of this narrow bandgap are discussed based on the chemical bonding nature probed by 6 keV hard X-ray photoemission spectroscopy, hybrid density functional calculations, and the ligand theory. One origin is the direct As–As hybridization between adjacent [ZnAs] layers, which leads to a secondary splitting of As 4p levels and raises the valence band maximum. The other is that the nonbonding Ba 5d_<i>x</i>²_{–<i>y</i>²} orbitals form an unexpectedly deep conduction band minimum (CBM) in β-BaZn₂As₂ although the CBM of LaZnAsO is formed mainly of Zn 4s. These two origins provide a quantitative explanation for the bandgap difference between β-BaZn₂As₂ and LaZnAsO

Electronic Structure of Above-Room-Temperature van der Waals Ferromagnet Fe₃GaTe₂

Fe3GaTe2, a recently discovered van der Waals ferromagnet, demonstrates intrinsic ferromagnetism above room temperature, necessitating a comprehensive investigation of the microscopic origins of its high Curie temperature (TC). In this study, we reveal the electronic structure of Fe3GaTe2 in its ferromagnetic ground state using angle-resolved photoemission spectroscopy and density functional theory calculations. Our results establish a consistent correspondence between the measured band structure and theoretical calculations, underscoring the significant contributions of the Heisenberg exchange interaction (Jex) and magnetic anisotropy energy to the development of the high-TC ferromagnetic ordering in Fe3GaTe2. Intriguingly, we observe substantial modifications to these crucial driving factors through doping, which we attribute to alterations in multiple spin-splitting bands near the Fermi level. These findings provide valuable insights into the underlying electronic structure and its correlation with the emergence of high-TC ferromagnetic ordering in Fe3GaTe2