Dresden 2009 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 29: Correlated Electrons: Low-dimensional Systems - Materials 2

TT 29.15: Talk

Wednesday, March 25, 2009, 18:00–18:15, HSZ 301

Quantum phase transitions in Ca₃Ru₂O₇ — •Oliver Welzel¹, Patricia Alireza¹, Carsten Albrecht², Naoki Kikugawa³, Andrew Mackenzie³, and Malte Grosche¹ — ¹Cavendish Laboratory, Cambridge, UK — ²Royal Holloway, University of London, Egham, UK — ³School of Physics and Astronomy, University of St. Andrews, UK

The strongly correlated bilayer ruthenate Ca₃Ru₂O₇ undergoes first a magnetic transition (T_N=56 K, Q=(0,0,1/2)) and then a structural transition (T_S = 48 K) on cooling. At low temperature, this material exhibits very small Fermi surface pockets, consistent with its low carrier density.

We follow the evolution of the low temperature state of Ca₃Ru₂O₇ with pressure: The structural transition is rapidly suppressed, and T_S extrapolates to zero at p_c1≃ 35  kbar. The magnetic transition is also suppressed. T_N extrapolates towards a critical pressure of p_c2≃ 55 kbar, but above 40 kbar it is replaced by signatures of a new ordered phase with an onset temperature of about T_X≃ 25 K. This new ordered phase, in turn, appears to be suppressed near p_c3≃ 80  kbar.

We explore the nature of the high pressure state of Ca₃Ru₂O₇ in a series of high pressure measurements of the resistivity, magnetic susceptibility and magnetisation, and investigate, in particular, the vicinity of the quantum critical point, p_c3.