Fermi Surface Reconstruction by Dynamic Magnetic Fluctuations and   Spin-Charge Separation Near an O(3) Quantum Critical Point
  Stimulated by the small/large Fermi surface controversy in the cuprates we consider a small number of holes injected into the bilayer antiferromagnet. The system has an O(3) quantum critical point (QCP) separating the magnetically ordered and the magnetically disordered phases. We demonstrate that nearly critical quantum magnetic fluctuations can change the Fermi surface topology and also lead to spin charge separation (SCS) in two dimensions. We demonstrate that in the physically interesting regime there is a magnetically driven Lifshitz point (LP) inside the magnetically disordered phase. At the LP the topology of the hole Fermi surface is changed. The position of the LP, while being close to the position of the QCP is generally different. Dependent on the additional hole hopping integrals $t^{\prime}$ and $t^{\prime\prime}$, the LP can be located either in the magnetically ordered phase and/or in the magnetically disordered phase. We also demonstrate that in this regime the hole spin and charge necessarily separate when approaching the QCP. The considered model sheds light on generic problems concerning the physics of the cuprates. 
Michael Holt, Jaan Oitmaa, Wei Chen, Oleg P. Sushkov
cond-mat.supr-con cond-mat.str-el