Peierls insulators and Luttinger liquids in atomic wires on substrates

Eric Jeckelmann, Institute of Theoretical Physics, Leibniz Universität Hannover

22.02.2017 at 15:00 

Quasi-1D electron systems can be realized in good approximation in linear atomic wires deposited on the surface of a semiconducting substrate. The interpretation of experiments with theories for 1D systems is often controversial,  however. A fundamental issue is that we have a poor understanding of the effects of the coupling between an atomic wire and its 3D substrate on phenomena such as the Peierls instability or the Luttinger liquid behavior of 1D conductors.
We discuss two investigations of this issue.
First, the grand-canonical Peierls transition is analyzed thoroughly within the Su-Schrieffer- Heeger (SSH) model. Starting from a generalized SSH-like model inferred from first-principles simulations, we show that the metal-insulator transition in In/Si(111) can be seen as a firstorder grand canonical Peierls transition in which the substrate acts as an electron reservoir for the wires. This approach explains naturally the existence of a metastable metallic phase over a wide temperature range below the critical temperature and the sensitivity of the transition to doping.
Second, we propose 3D lattice models for isolated atomic wires on substrates and show that they can be mapped onto narrow ladder models that can be investigated with well-established methods for 1D correlated systems. This approach is illustrated with a systematic study of a wire with a Hubbard-type coupling using the density-matrix renormalization group and quantum Monte Carlo simulations. We show that typical 1D features can be observed in these models, such as Mott insulators with gapless spinon excitations and 1D conductors with Luttinger liquid behavior. Thus effective narrow ladder models provide us with a promising approach to investigate correlation effects in wire-substrate systems.
References:
[1] Eric Jeckelmann, Simone Sanna, Wolf Gero Schmidt, Eugen Speiser, and Norbert Esser, Phys.
Rev. B 93 , 241407(R) (2016)
[2] Anas Abdelwahab, Eric Jeckelmann, and Martin Hohenadler, Phys. Rev. B 91 , 155119 (2015)