Emergent magnetism in niobium diselenide

Sustainable development pairs the rapid increase in technological advancements with addressing environmental challenges. Within this landscape, nanotechnology offers interesting and exciting solutions via the exploration and engineering of materials directly at the nanoscale. Progress in logic units, sensors, and energy harvesting endeavors to enhance scalability and energy efficiency, encompassing nanosensors, spintronic-based data and logic devices,  and optoelectronic components.

At the two-dimensional limit, the interplay between structural and electronic degrees of freedom and the occurrence of instabilities gives rise to interesting phenomena, such as two-dimensional magnetism and Ising superconductivity. Because they occur due to the reduced dimensionality or by the formation of heterostructures, these manifestations are referred to as emergent phenomena.

In this talk, I will delve into the class of materials known as transition metal dichalcogenides, and in particular into the paradigmatic case of 2H-NbSe$_2$. After an introduction focused on its collective phases, superconductivity and charge density waves, I will showcase a selection of my results based on density functional theory models. I will delve into the effect of strain, stacking and doping on the formation of charge density waves, their symmetry and modulation, as well as the possibility of inducing a small spin polarisation. In showing how magnetism can be stabilized in monolayers, I will hover on the Stoner model for ferromagnetism and Van Hove singularities, which are of fundamental interest in materials with electronic correlation and superconductivity.

Short Bio

Fabrizio Cossu completed his doctoral studies in 2009 at the University of Cagliari, Italy. His core expertise is on ab-initio structural and electronic calculations. His research work is focussed on magnetic orders, electronic correlation and collective electronic excitations in two-dimensional materials and oxide heterostructures.

He has worked in Uppsala University (Sweden), King Abdullah University of Science and Technology (Saudi Arabia), the Asia Pacific Center for Theoretical Physics (Republic of Korea), Kangwon National University (Republic of Korea), University of Aberdeen and University of Hertfordshire.

Throughout his career, Dr. F. Cossu has secured independent funding from the National Research Foundation of Korea for two individual projects and has co-supervised PhD students and junior researchers of several countries.