Non-Fermi liquid behaviour at the orbital-ordering quantum critical point in the two-orbital model
Department of Physics, University of Illinois at Urbana-Champaign - Urbana, IL 61801, USA
Received: 22 February 2013
Accepted: 23 February 2013
The critical behaviour of a two-orbital model with degenerate dxz and dyz orbitals is investigated by multi-dimensional bosonization. We find that the corresponding bosonic theory has an overdamped collective mode with dynamical exponent z = 3, which appears to be a general feature of a two-orbital model and becomes the dominant fluctuation in the vicinity of the orbital-ordering quantum critical point. Since the very existence of this z = 3 overdamped collective mode induces non-Fermi liquid behaviour near the quantum critical point, we conclude that a two-orbital model generally has a sizable area in the phase diagram showing non-Fermi liquid behaviour. Furthermore, we show that the bosonic theory resembles the continuous model near the d-wave Pomeranchuk instability, suggesting that orbital order in a two-orbital model is identical to nematic order in a continuous model. Our results can be applied to systems with degenerate dxz and dyz orbitals such as iron-based superconductors and bilayer strontium ruthenates Sr3Ru2O7.
PACS: 05.30.Rt – Quantum phase transitions / 74.70.Xa – Pnictides and chalcogenides
© EPLA, 2013