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The Dynamic Ligand Field of a Molecular Qubit: Decoherence Through Spin–Phonon Coupling

Mirzoyan, Ruben and Hadt, Ryan G. (2020) The Dynamic Ligand Field of a Molecular Qubit: Decoherence Through Spin–Phonon Coupling. Physical Chemistry Chemical Physics, 22 (20). pp. 11249-11265. ISSN 1463-9076.

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Quantum coherence of S = 1/2 transition metal-based quantum bits (qubits) is strongly influenced by the magnitude of spin–phonon coupling. While this coupling is recognized as deriving from dynamic distortions about the first coordination sphere of the metal, a general model for understanding and quantifying ligand field contributions has not been established. Here we derive a general ligand field theory model to describe and quantify the nature of spin–phonon coupling terms in S = 1/2 transition metal complexes. We show that the coupling term for a given vibrational mode is governed by: 1) the magnitude of the metal-based spin–orbit coupling constant, 2) the magnitude and gradient in the ligand field excited state energy, and 3) dynamic relativistic nephelauxetic contributions reflecting the magnitude and gradient in the covalency of the ligand–metal bonds. From an extensive series of density functional theory (DFT) and time-dependent DFT (TDDFT) calculations calibrated to a range of experimental data, spin–phonon coupling terms describing minimalistic D_(4h)/D_(2d) [CuCl₄]²⁻ and C_(4v) [VOCl²⁻ complexes translate to and correlate with experimental quantum coherence properties observed for Cu(II)- and V(IV)-based molecular qubits with different ligand sets, geometries, and coordination numbers. While providing a fundamental framework and means to benchmark current qubits, the model and methodology described herein can be used to screen any S = 1/2 molecular qubit candidate and guide the discovery of room temperature coherent materials for quantum information processing.

Item Type:Article
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URLURL TypeDescription Information Paper
Mirzoyan, Ruben0000-0002-2334-4012
Hadt, Ryan G.0000-0001-6026-1358
Additional Information:© 2020 the Owner Societies. Submitted 14 Feb 2020; Accepted 19 Mar 2020; First published 19 Mar 2020. We acknowledge Prof. Edward Solomon, Dr. Alec Follmer, Roman Korol, and Nicholas Higdon for helpful discussions. Financial support from Caltech and the Dow Next Generation Educator Fund is gratefully acknowledged. There are no conflicts to declare.
Funding AgencyGrant Number
Dow Next Generation Educator FundUNSPECIFIED
Subject Keywords:Quantum Coherence; Spin–Phonon Coupling; Ligand Field Theory; Qubits; Density Functional Theory; Time-dependent density functional theory
Issue or Number:20
Record Number:CaltechAUTHORS:20191105-101953113
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Official Citation:The Dynamic Ligand Field of a Molecular Qubit: Decoherence Through Spin–Phonon Coupling. Phys. Chem. Chem. Phys., 2020, 22, 11249-11265; doi: 10.1039/D0CP00852D
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:99669
Deposited By: Tony Diaz
Deposited On:05 Nov 2019 18:32
Last Modified:25 Jun 2021 21:33

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