Lifshitz phase transitions in a one-dimensional Gamma model.

In this paper, we study quantum phase transitions and magnetic properties of a one-dimensional spin-1/2 Gamma model, which describes the off-diagonal exchange interactions between edge-shared octahedra with strong spin-orbit couplings along the sawtooth chain. The competing exchange interactions between the nearest neighbors and the second neighbors stabilize the semimetallic ground state in terms of spinless fermions, and give rise to a rich phase diagram, which consists of three gapless phases. We find distinct phases are characterized by the number of Weyl nodes in the momentum space, and such changes in the topology of the Fermi surface without symmetry breaking produce a variety of Lifshitz transitions, in which the Weyl nodes situating at k=π change from type I to type II.

A three-dimensional Zn coordination network based on 5,5'-methylenebis(2,4,6-trimethylisophthalic acid) and 2,7-bis(1H-imidazol-1-yl)fluorene: synthesis, structure and luminescence properties.

In recent years, coordination polymers constructed from multidentate carboxylate ligands and N-containing ligands have attracted much attention since these ligands can adopt a rich variety of coordination modes which can lead to crystalline products with intriguing structures and interesting properties. A new coordination polymer, namely poly[[diaqua[μ-2,7-bis(1H-imidazol-1-yl)fluorene-κN:N][μ-5,5'-methylenebis(3-carboxy-2,4,6-trimethylbenzoato)-κO:O]zinc(II)] hemihydrate], {[Zn(CHO)(CHN)(HO)]·0.5HO}, 1, was prepared by the self-assembly of Zn(NO)·6HO with 5,5'-methylenebis(2,4,6-trimethylisophthalic acid) (HBTMIPA) and 2,7-bis(1H-imidazol-1-yl)fluorene (BIF) under solvothermal conditions.