Strongly correlated electron systems exhibit a wealth of effects such as magnetic ordering, mixed valence, charge ordering phase transition, metal-insulation transition etc. The discovery of high-temperature superconductivity in lightly-doped transition-metal oxide antiferromagnets teaches us that these materials can do other remarkable things as well, which still need to be explored. In this talk I will review few results obtained along one particular research direction, motivated by the question: Is there something specific in the magnetism of transition metal oxides which is a prerequisite for the appearance of high-Tc superconductivity? Interestingly, some of these materials show low-dimensional magnetic properties due to strongly reduced electron interaction along one or two crystallographic directions. For example, as a consequence of quasi one-dimensionality, the spin-dimerization may occur in the spin-chains (spin-Peierls transition) or spin-ladders leading to the non-magnetic ground states at low temperatures. These structures exhibit complex excitation spectra which can be studied by Raman spectroscopy.

            Firstly, I will discuss what kind of quantum effects are observed in the magnetic systems with restricted geometry, in particular the antiferromagnetic, S=1/2, two-leg-ladder, CaV₂O₅.  Then, I will analyze the electronic order-disorder effects in the Raman spectra of NaV₂O₅, and discuss the charge ordering phase transition in this compound. Finally, I will present the orbital dimerization in NaTiSi₂O₆. I will argue that the novel type of the phase transition at T=210 K can be regarded as an orbital analogue of the spin-Peierls phase transition.

• Legal notice:
  

  Copyright (c) Pielaszek Research, all rights reserved.
  The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
  In every case, proper references including Author(s) name(s) and URL of this webpage: https://science24.com/paper/16333 must be provided.