A seminar given by
Dr. Antonio TEJEDA
Researcher at the Laboratoire de Physique des Solides (Université Paris-Saclay/CNRS)
Many-body effects in phase transitions in Sn/Ge(111) as a function of the temperature
Abstract: We present here an investigation on the phase transitions of 0.33 ML of Sn on Ge(111) at low temperature. We have identified a (3 × 3) phase, characterized by a charge ordering settled by electronic correlation, which appears between the known metallic- (3 × 3) and the root3 insulating phase at very low temperature, The vertical distortion characteristic of the (3 × 3) phase is lost across the phase transition,. We identify the atomistic mechanism behind the stabilization of this charge ordered insulating phase and interpret these findings on the basis of theoretical calculations. Moreover, our experimental and theoretical results show a giant electron-phonon interaction at the (3×3) phase between 150 and 120 K. The electron-phonon interaction in α−Sn/Ge(111)−(3×3) is unusually large, since we find that theoretically λ, the electron mass enhancement for the half-filled band, is λ=1.3. This result is in good agreement with the experimental value obtained from high-resolution angle-resolved photoemission spectroscopy measurements, which yield λ=1.45±0.1. The giant electron-phonon interaction can be considered at least partially responsible for the different phases that this system shows at very low temperature.
Figure (a) Second derivative of the ARPES data along the ΓM3×3 direction. (b) Left: Fermi level region from (a). Right: Momentum distribution curves corresponding to the red lines shown in the left panel. (c) Experimental points and fit to the bare (black line) and the renormalized (dashed purple line) bands. The kink associated to electron phonon coupling is visible.
1) R. Cortés et al. Phys. Rev. Lett. 96, 126103 (2006).
2) R. Cortés et al. Phys. Rev. B 88, 125113 (2013).
3) M.N. Nair et al. Phys. Rev. B 107, 045303 (2023).
Bio: Antonio TEJEDA’s research focuses on the control of electronic properties by structural modifications. His favorite objects are surfaces and other two-dimensional systems where physical properties can be significantly affected by defects, phase transitions or quantum confinement in nanostructures.
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