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

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 predicted tunnel splittings from instanton theory, the number density, dipole moment, and coupling to external strain of the discovered motifs are consistent with experiments.

arXiv comment10 pages, 9 figures. Final version, accepted for publication in Physical Review B

References in corpus (28)

• Escaping free-energy minima
• Decoherence in Josephson Qubits from Dielectric Loss
• Decoherence in Josephson Qubits from Junction Resonances
• How do the properties of a glass depend on the cooling rate? A computer simulation study of a Lennard-Jones system
• Nonlinear Quantum Optomechanics via Individual Intrinsic Two-Level Defects
• Tunnel splittings for one dimensional potential wells revisited
• Quantum two-level systems in Josephson junctions as naturally formed qubits
• Tunable Quantum Beam Splitters for Coherent Manipulation of a Solid-State Tripartite Qubit System
• Measuring the temperature dependence of individual two-level systems by direct coherent control
• Cryogenic properties of optomechanical silica microcavities
• Bulk and Surface Tunneling Hydrogen Defects in Alumina
• Quantum two level systems and Kondo-like traps as possible sources of decoherence in superconducting qubits
• The "Tunneling Two-Level Systems" Model of the Low-Temperature Properties of Glasses: Are "Smoking-Gun" Tests Possible?
• Quantum Friction in Nanomechanical Oscillators at Millikelvin Temperatures
• Polaronic model of Two Level Systems in amorphous solids
• Damping in high-frequency metallic nanomechanical resonators
• One- and two-photon spectroscopy of a flux qubit coupled to a microscopic defect
• Microscopic Model of Critical Current Noise in Josephson Junctions
• What is moving in silica at 1 K? A computer study of the low-temperature anomalies
• Quantum decoherence of a charge qubit in a spin-fermion model
• Delocalised oxygen as the origin of two-level defects in Josephson junctions
• Rabi spectroscopy of a strongly driven qubit-fluctuator system
• Multi-level Spectroscopy of Two-Level Systems Coupled to a dc SQUID Phase Qubit
• Microscopic model of critical current noise in Josephson-junction qubits: Subgap resonances and Andreev bound states
• Evidence for hydrogen two-level systems in atomic layer deposition oxides
• Local Properties of the Potential Energy Landscape of a Model Glass: Understanding the Low Temperature Anomalies
• Influence of polarizability on metal oxide properties studied by molecular dynamics simulations
• Entangling microscopic defects via a macroscopic quantum shuttle

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• A 3D investigation of delocalised oxygen two-level defects in Josephson junctions