SIS - X09LA: Surface / Interface Spectroscopy

Flows need sources and sinks. That’s why, in a new class of exotic materials called Weyl semimetals, the sources and sinks of Berry curvature – dubbed Weyl points – were believed to exist only in pairs. Now researchers at PSI have observed unpaired Weyl points for the first time in a crystalline solid. This discovery, which upends conventional thinking and the so-called Nielson-Niomiya no-go theorem, demonstrates the unique properties of "nodal wall" Weyl semimetals in comparison to conventional Weyl systems having only zero-dimensional Weyl nodes.

Within this synergetic collaboration, PSI scientists have investigated the correlation between magnetic and electronic ordering in NdNiO3 by tuning its properties through proximity to a ferromagnetic manganite layer. The main outcome is that the stray magnetic field from the manganite layer causes a novel ferromagnetic-metallic (FM-M) phase in NNO. This work demonstrates the utilization of heterostructure engineering for creating novel quantum phases.

Researchers from University of Zurich describe the experimental observation of a new orthorhombic structural phase in the superconducting iron-pnictide compound Pr₄Fe₂As₂Te_0.88O₄. In contrast to nematicity found in underdoped iron pnictides this phase transition is not electronically driven.