1 A. A. Katanin a,b,c and A. P. Kampf c 2004 a Max-Planck Institut für Festkörperforschung, Stuttgart b Institute of Metal Physics, Ekaterinburg, Russia c Theoretische Physik III, Institut für Physik, Universität Augsburg Anomalous self-energy and pseudogap formation near an antiferromagnetic instability

2 Introduction PM (Fermi liquid, well-defined QP) metallic AF (n  1) T *  0 PM metallic AF T*T*   C exp(T * /T), T < T *   C exp(T * /T), T < T * T   dSC T 2-nd order QPT 1-st order QPT Previous studies: SF model (A. Abanov, A. Chubukov, and J. Schmalian) 2D Hubbard model: DCA (Th. Maier, Th. Pruschke, and M. Jarrell) FLEX (J. J. Deisz et al., A. P. Kampf) TPSC (B. Kyung and A. M.-S. Tremblay) What are the changes in the electronic spectrum on approaching an AF metallic phase in 2D ? RC

3 Cuprates: experimental results Pseudogap regime – the spectral weight at the Fermi level is suppressed. SC AFM PG Partly “metallic” behavior even at very low hole doping From: T. Yoshida et al., Phys. Rev. Lett. 91, (2003).

4 The model and AF order t'/t n   AF order at large U in a nearly half-filled band – AF Mott insulator   AF order due to peculiarities of band structure – Slater antiferromagnetism: n tt ()() The model: van Hove band fillings  C. J. Halboth and W. Metzner Phys. Rev. B 61, 7364 (2000) C. Honerkamp, et al., Phys. Rev. B 63, (2001) Two possibilities to have AF order:

5 Self-energy: mean-field results Im   i    Re     k+Q  0   Im  Re   k+Q    k+Q  0 A B A B A B n  n vH n  n vH Q

6 The functional RG =.... = Discretization of the momentum dependence of the interaction

7 Self-energy at vH band fillings Spectral properties are strongly anisotropic around the Fermi surface The quasiparticle concept is violated at k F =( ,0) and valid in a narrow window around  for other k F The spectral properties are mean-field like for k=( ,0) while they are qualitatively different from MF results for other k F

8 Self-energy near vH band fillings Unlike vH band fillings, magnetic fluctuations suppress spectral weight, but are not sufficient to drop spectral weight to zero. The quasiparticle concept is valid in a narrow window around  for all k F Similiarity with the PM – PI, U < U c Hubbard sub-bands Mott-Hubbard DMFT picture Quasiparticle peak, Z  0

9 Conclusions The spectral weight is anisotropic around FS and decreases towards ( ,0). At the ( ,0) point two-peak pseudogap structure of the spectral function arises. At the other points the spectral function has three-peak form Weak U Strong U ( ,0) ( ,  ) ( ,0) ( ,  ) Spectral weight transfer Hubbard sub-bands Magnetic sub-bands Possible scenario for strong coupling regime in the nearly half-filled 2D Hubbard model Quasiparticle peak Therefore, at f inite t' and away from half filling