Dresden 2009 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 15: Correlated Electrons: Metal-Insulator Transition 2

TT 15.5: Talk

Tuesday, March 24, 2009, 10:45–11:00, HSZ 301

LDA+DMFT study of the Sn/Si(111)(√3×√3)R30^∘ surface states — •Sergej Schuwalow, Lewin Boehnke, and Frank Lechermann — I. Institut für Theoretische Physik, Universität Hamburg, 20355 Hamburg, Germany

Experimental studies [1] and LDA+U calculations [2] for the Sn/Si(111)(√3×√3)R30^∘ surface suggest a Mott-insulating surface state originating dominantly from strongly correlated Sn (5p) orbitals below about 70K. Interestingly, the Sn atoms form a 1/3 monolayer on an effective triangular lattice. Hence the issue of spin liquid physics may arise due to possible frustration effects.

In the scope of this work, we have first obtained an effective Hamiltonian for the surface states of this system in terms of maximally localized Wannier functions from LDA calculations. From there, we performed DMFT calculations for both a 1-band and a 3-band effective Hamiltonian to map out the temperature-dependent behavior of the spectral function close to the suggested metal-insulator transition and to investigate the importance of the different surface bands. In the case of the 3-band Hamiltonian, the full U matrix was used for the calculations. Finally, we compared the results of our dynamical approach to those obtained within the static LDA+U formalism.

[1] S. Modesti et al., PRL 98, 126401 (2007)

[2] G. Profeta and E. Tosatti, PRL 98, 086401 (2007)