Identification of structural motifs as tunneling two-level systems in amorphous alumina at low temperatures

Alejandro Pérez Paz, Irina V. Lebedeva, Ilya V. Tokatly, Angel Rubio

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)

Abstract

One of the most accepted models that describe the anomalous thermal behavior of amorphous materials at temperatures below 1 K relies on the quantum mechanical tunneling of atoms between two nearly equivalent potential energy wells forming a two-level system (TLS). Indirect evidence for TLSs is widely available. However, the atomistic structure of these TLSs remains an unsolved topic in the physics of amorphous materials. Here, using classical molecular dynamics, we found several hitherto unknown bistable structural motifs that may be key to understanding the anomalous thermal properties of amorphous alumina at low temperatures. We show through free energy profiles that the complex potential energy surface can be reduced to canonical TLSs. The tunnel splitting predicted from instanton theory, the number density, dipole moment, and coupling to external strain of the discovered motifs are consistent with experiments.

Original languageEnglish
Article number224202
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume90
Issue number22
DOIs
Publication statusPublished - Dec 4 2014
Externally publishedYes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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