Veranstaltungsdetails

26.10.2010, 17:00
Jungiusstr. 11, Hörsaal AP

SFB 668 - Kolloquium

Prof. Jean-Pierre Gauyacq (Université Paris-Sud) :

Excitation of finite chains of magnetic atoms by tunnelling electrons: A view at quantized spin waves

Excitation of finite chains of magnetic atoms adsorbed on a surface by tunnelling electrons from an STM (Scanning Tunnelling Microscope) tip is studied using a Heisenberg Hamiltonian description of the magnetic couplings along the chain. Magnetic transitions are described using a recently developed strong coupling approach that has been successfully applied to individual magnetic adsorbates (Phys.Rev.Lett. 103 (2009) 176601, Phys.Rev. B 81 (2010) 165423). Model chains of magnetic atoms are considered, both with ferro- and antiferromagnetic couplings. The magnetic excitations induced in the chain by tunnelling electrons can be seen as spin waves quantized in the finite size object. The energy and momentum spectra of the spin waves excited in an idealized infinite chain by tunnelling electrons are determined from the results on the finite chains. The ferro and antiferromagnetic couplings lead to different excitation schemes. In particular, in the antiferromagnetic case, excitations linked to the entanglement of the chain ground state are evidenced.