Signatures of the Tomonaga Luttinger liquid in quasi-one dimensional materials : The case of molybdenum purple bronze

Orateur : Piotr CHUDZINSKI (Regensburg University, Germany)

In my talk I would like to present recent achievements in the theoretical understanding of photoemission measurements done on various quasi-1D systems. The first material under consideration is a transition metal oxide, the purple bronze $Li_0.9Mo_6O_19$, for which a thermodynamic phase transition into a superconducting state takes place at a relatively low temperature of 1.9K. As indicated by many experiments, its carriers are very 1-dimensional. The overall DFT band structure agrees reasonably well with existing photoemission data but in order to understand better the dimensional crossover we focused on details of the dispersion perpendicular to the main dispersive direction. Based on this, we derive an effective low energy theory within the Tomonaga Luttinger liquid framework. We estimate the strength of the possible instabilities and the values of charge mode compressibilities. Our aim is to understand the experimental findings, in particular the ones which are certainly lying within the 1D regime. I will discuss the validity of our approach and further perspectives for the lower energy phases. If time permits I will introduce another quasi-1D system, $NbSe_3$ which has very different physics. Here upon lowering the temperature there are two charge density wave transitions at 145 K and 59 K. Nevertheless some carriers manage to remain gapless and these are the focal point of interest.

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