A correlated ferromagnetic polar metal by design.

Polar metals have recently garnered increasing interest because of their promising functionalities. Here we report the experimental realization of an intrinsic coexisting ferromagnetism, polar distortion and metallicity in quasi-two-dimensional Ca3Co3O8. This material crystallizes with alternating stacking of oxygen tetrahedral CoO4 monolayers and octahedral CoO6 bilayers. The ferromagnetic metallic state is confined within the quasi-two-dimensional CoO6 layers, and the broken inversion symmetry arises simultaneously from the Co displacements. The breaking of both spatial-inversion and time-reversal symmetries, along with their strong coupling, gives rise to an intrinsic magnetochiral anisotropy with exotic magnetic field-free non-reciprocal electrical resistivity. An extraordinarily robust topological Hall effect persists over a broad temperature-magnetic field phase space, arising from dipole-induced Rashba spin-orbit coupling. Our work not only provides a rich platform to explore the coupling between polarity and magnetism in a metallic system, with extensive potential applications, but also defines a novel design strategy to access exotic correlated electronic states.

Surface Structures of Mn3O4 and the Partition of Oxidation States of Mn.

The Mn(III) ions at Mn3O4 surface are hypothesized to contribute to catalytic activity in oxygen reduction reaction. However, the surface structure and stability of Mn3O4 are far less understood. Here, the atomic structures of the widespread (101) and (001) surfaces of Mn3O4 are determined by combining aberration-corrected transmission electron microscopy and DFT calculations. The surface stabilization mechanisms and the oxidation states of Mn are revealed and correlated to the catalytic activity of the surfaces. The results show that the (101) surface undergoes a subsurface reconstruction, forming a rock-salt-type surface layer. The Mn(III) ions are in the outermost layer of the (001) surface but in the subsurface of the (101) surface. The surface partition of the Mn(III) ions provides a microscopic understanding to the observed higher catalytic activity of the (001) surface relative to the (101) surface and would contribute to further development of novel catalysts based on Mn3O4.

Surface termination and stoichiometry of LaAlO3(001) surface studied by HRTEM.

As an important topic of condensed matter physics, metal oxide surfaces often exhibit exotic properties such as high catalytic activity, enhanced ferroelectricity and electronic phase transition, originating from the different local symmetry with respect to the bulk. As the structure determination of oxide surfaces presents challenges to conventional surface science techniques like scanning tunneling microscopy, aberration-corrected transmission electron microscopy (TEM) has been increasingly used to solve structures of oxide surfaces. In this work, the (001) surface of LaAlO3, one of the most used components of oxide heterostructures, has been investigated. Our TEM experiments and extensive image simulations show that the La-O terminated LaAlO3(001) surface undergoes significant reconstructions, forming La vacancies on the surface layer. Energetically, the LaAlO3(001) surface is stable with the reconstructed La-O termination in a wide range of oxygen chemical potentials. Polarity compensation, reduced density of states at the Fermi level and bond enhancement of subsurface oxygen anions all contribute to the stabilization of the reconstructed surface.

Intrahepatic biliary cystadenoma: A case report.

BACKGROUND: Biliary cystadenoma (BCA) is a rare benign tumor, accounting for only 5% of reported cystic lesions of the liver. Given its potential for malignancy and high rate of recurrence, surgical resection is the preferred treatment. Therefore, early and accurate preoperative diagnosis is critical to the choice of treatment. We here report the first male case of BCA in our hospital, diagnosed by our team and confirmed by pathological biopsy. This article aims to improve the understanding of this disease and help make a correct diagnosis to better manage it. CASE SUMMARY: A 58-year-old man with irregular abdominal discomfort came to our clinic and was found to have a distended abdomen during physical examination. Computed tomography and magnetic resonance imaging both showed a huge cystic mass in the liver. The patient underwent left hepatic lobectomy, cholecystectomy, and liver cyst fenestration, and most of the masses had decreased in size as of the 6-mo follow-up. The pathological diagnosis was consistent with BCA, and no recurrence was detected after the surgery. BCA occurred mainly in middle-aged women. To the best of our knowledge, this patient is the 11th male case of BCA reported in the literature. CONCLUSION: The combination of magnetic resonance imaging and magnetic resonance cholangiopancreatography is of great significance for the early accurate diagnosis of the disease and the choice of surgical methods.

Subsurface reconstruction and saturation of surface bonds.

Surface reconstructions and stabilization mechanisms have been great challenges for insulators. Based on accurate determination of the long-sought atomic structure of the spinel (1 1 1) surface, here we show that the surface is stabilized by an unconventional mechanism. In general, solid surfaces have unsaturated chemical bonds and are prone to atomic reconstruction to saturate them. The spinel (1 1 1) surface, however, has the surface bonds fully saturated, while the unsaturated bonds remain only in the subsurface. It undergoes a reconstruction that keeps the topmost atomic layer unchanged, but has the subsurface atoms completely rearranged. Such a reconstruction results in a perfect compensation of the surface polarity and a large reduction in the surface energy. This work provides surprising insights into the surface stability and physical and chemical behaviors of complex oxides and insulators.