Seminarium Fizyki Materii Skondensowanej

In the first part of my talk I will address a question: what happens when electrons’ motion becomes confined to one direction? Can we describe them? The answer, at least in the low energy limit, is the sine-Gordon model on the top of Tomonaga-Luttinger liquid which allows to find all correlation functions no matter how strong correlations are, and the resulting Berezinskii-Kosterlitz-Thouless (BKT) phase diagram. In the second part I will move on to introduce a real material where such situation is realized. It belongs to a family of molybdenum purple bronzes, whose other members were early shown to be Peierls-CDW compounds, while the physics of the Li-compound has remained elusive. From the beginning of 21st century experimental evidence has been mounting, indicating that this material may be a rare realization of Tomonaga-Luttinger liquid in a solid state setting. However, the lowest energy physics does not obey this canonical picture and the origin of a mysterious upturn of resistivity was understood only few years ago. Then I will move on to the most recent findings that directly probe the parent state of superconductivity. We were able to show that the Li0.9Mo6O17 is in fact in the higher symmetry state, right on the edge of Mott insulating region in the BKT picture. I will explain how the specific properties of Li0.9Mo6O17 enabled us to measure directly the BKT renormalization group flow and what conclusions we were able to draw from that.