Scientific Highlights & News

Using soft x-ray angle-resolved photoemission spectroscopy we probed the bulk electronic structure of T_d-MoTe₂. We found that on-site Coulomb interaction leads to a Lifshitz transition, which is essential for a precise description of the electronic structure. A hybrid Weyl semimetal state with a pair of energy bands touching at both type-I and type-II Weyl nodes is indicated by comparing the experimental data with theoretical calculations.

Determining the fate of the Pauling entropy in the classical spin ice material Dy₂Ti₂O₇ with respect to the third law of thermodynamics has become an important test case for understanding the existence and stability of ice-rule states in general. The standard model of spin ice—the dipolar spin ice model—predicts an ordering transition at T ≈ 0.15K, but recent experiments by Pomaranski et al.

La_1/3Sr_2/3FeO₃ is reported to show a 2Fe⁴⁺ → Fe³⁺ + Fe⁵⁺ charge disproportionation (CD) accompanied by Fe³⁺/Fe⁵⁺ charge ordering (CO) and a metal-insulator (MI) transition at 200 K [1]. The MI transition was ascribed to CD and CO. Based on the CO, the magnetic structure was reported to be P-3m1 or P1 from the neutron diffraction studies performed at 50 K and 15 K, respectively [2]. The former seems not to be a correct solution since the presence of rotoinversion -3 is incompatible with the claimed collinear magnetic structure, with the collinear moments in the ab-plane in R-3c metric; and the latter might be a correct solution, but without any symmetry restrictions in space group P1.

The study of interacting spin systems is of fundamental importance for modern condensed-matter physics. On frustrated lattices, magnetic exchange interactions cannot be simultaneously satisfied, and often give rise to competing exotic ground states. The frustrated two-dimensional Shastry–Sutherland lattice realized by SrCu₂(BO₃)₂ is an important test to our understanding of quantum magnetism.