Low-energy quantum dynamics of atoms at defects. Interstitial oxygen in silicon

TL;DR

This paper investigates the low-energy quantum behavior of interstitial oxygen impurities in silicon using path-integral Monte Carlo simulations, revealing regimes of classical and anharmonic dynamics separated by a sharp transition.

Contribution

It introduces a detailed analysis of the quantum dynamics of impurities in solids, highlighting the transition between classical and anharmonic regimes and proposing an effective one-body Hamiltonian approach.

Findings

Identification of classical and anharmonic regimes separated by a sharp transition.

Development of an adiabatic potential approximation for the many-nuclei problem.

Insights into the geometry and dynamics of interstitial oxygen in silicon.

Abstract

The problem of the low-energy highly-anharmonic quantum dynamics of isolated impurities in solids is addressed by using path-integral Monte Carlo simulations. Interstitial oxygen in silicon is studied as a prototypical example showing such a behavior. The assignment of a "geometry" to the defect is discussed. Depending on the potential (or on the impurity mass), there is a "classical" regime, where the maximum probability-density for the oxygen nucleus is at the potential minimum. There is another regime, associated to highly anharmonic potentials, where this is not the case. Both regimes are separated by a sharp transition. Also, the decoupling of the many-nuclei problem into a one-body Hamiltonian to describe the low-energy dynamics is studied. The adiabatic potential obtained from the relaxation of all the other degrees of freedom at each value of the coordinate associated to the low-energy motion, gives the best approximation to the full many-nuclei problem.