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O: Fachverband Oberflächenphysik

O 2: Focussed session: Frontiers of electronic structure theory: Strong correlations from first principles I (jointly with TT)

O 2.4: Vortrag

Montag, 26. März 2012, 11:30–11:45, HE 101

Strength of the Hubbard U at metal and insulator surfaces — •Ersoy Sasioglu, Christoph Friedrich, and Stefan Blügel — Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany

The effective on-site Coulomb interaction (Hubbard U) between localized electrons at surfaces of solids is expected to be enhanced since the effective screening volume of the surface is reduced with respect to the bulk. By means of first-principles calculations in conjunction with the constrained random-phase approximation (cRPA) [1] within the full-potential linearized augmented-plane-wave (FLAPW) method [2] we show that this is indeed the case for simple metals and insulators but not necessarily for transition metals and insulators that exhibit pronounced surface states. In the latter case, the screening contribution from surface states as well as the influence of the band narrowing can increase the electron polarization to such an extent that the expected decrease resulting from the reduced effective screening volume is overcompensated. In some cases, the Hubbard U parameter is substantially reduced, e.g., by around 30% for the (100) surface of bcc Cr, contrary to the conventional wisdom. We show a systematic study for prototype materials including transition-metal surfaces.
E. Şaşioğlu, C. Friedrich, and S. Blügel, PRB 83, 121101(R) (2011).
http://www.flapw.de