Grand canonical Peierls transition in In/Si(111)

Abstract

Starting from a Su-Schrieffer-Heeger-like model inferred from first-principles simulations, we show that the metal-insulator transition in In/Si(111) is a first-order grand canonical Peierls transition in which the substrate acts as an electron reservoir for the wires. This model 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. Raman scattering experiments corroborate the softening of the two Peierls deformation modes close to the transition

Efficient PAW‐based bond strength analysis for understanding the In/Si(111)(8 × 2) – (4 × 1) phase transition

“…For the 4 × 1 phase the COHP analysis confirms the typical model of two regular outer zig‐zag chains while there are nearly no outermost linear bonds in contrast to the tight binding fitting results of Ref. [ ]. However, there are indeed strong bonds between the In atoms of the two zig‐zag rows which are a substantial ingredient for the SSH Hamiltonian in Ref.…”

“…Above about 120 K the In atoms arrange in metallic zigzag chains with 4 × 1 symmetry, see Figure . Whether or not this insulator‐metal transition can be classified as Peierls instability driven or not, and if it is a first‐ or second‐order phase transition is controversially discussed up to now …”

“…Jeckelmann et al developed a simplified 1D lattice model for the In nanowire, where they focus on the bonds within outermost linear In chains and within a central In zigzag chain, as indicated in the bottom of Figure . These bonds couple most strongly to the soft In chain rotary and shear modes, the Peierls amplitude modes in In/Si(111).…”

“…These bonds couple most strongly to the soft In chain rotary and shear modes, the Peierls amplitude modes in In/Si(111). The reduction of the In bonding configuration to these bonds allows for decoupling the nanowire system into three independent chains with Su–Schrieffer–Heeger (SSH) Hamiltonians that suggest to interpret the 4 × 1 → 8 × 2 phase change as first‐order grand canonical Peierls transition . Kim and Cho, conversely, stress the importance of bond‐breaking and bond‐making processes during the metal‐insulator transition of the indium atom wires and classify the latter as an exothermic surface reaction.…”

“…The mechanism and driving force for this phase transition has been controversially discussed since it's discovery. In particular, it is presently discussed whether the phase transition is of order‐disorder or displacive type, and whether it can be characterized as Peierls transition or should rather be addressed as an exothermic reaction with the consecutive bond‐breaking and bond‐making processes . The investigation of these questions will certainly profit from a quantitative investigation of the relevant bond strengths.…”