Phase Diagram near a Quantum Critical Point in Ultra pure Sr3Ru2O7

R. A. BORZI; S. A. GRIGERA; A. S. GREEN; R. S. PERRY; KIKUGAWA, N.; A. P. MACKENZIE

Warwick, Reino Unido.

Conferencia; A Century after Einstein; 2005

Warwick University

Crystalline disorder may play a major role in changing the nature or hiding the actual ground state of the layered ruthenate oxides. The single-layered Sr2RuO4, best known for its triplet superconductivity, has been a good example of this behavior. The same has proven to be true for the bilayered compound Sr3Ru2O7, which changed from a ferromagnetic metal to a paramagnetic Fermi liquid when improving its purity. A metamagnetic transition in these purer samples at fields near 7 T has lead to the understanding of a new type of quantum criticality with no associated symmetry breaking. Further decrease on the disorder of Sr3Ru2O7 single-crystals has allowed to measure quantum oscillations for the first time and furthermore, new physics seem to have emerged. Supported by susceptibility, magnetostriction, transport, and magnetisation measurements we will discuss on the phase diagram that develops near the quantum critical region. We show that simple Landau theory can account for many of the important features of the phase diagram, and gives important clues on the physical mechanisms that could be actually shaping it. It also evaluates the capacity of the ruthenate system to realize quantum tricritical behaviour.