Abstract

Quantum systems in contact with a thermal environment experience coherent and incoherent dynamics. These drive the system back toward thermal equilibrium after an initial perturbation. The relaxation process involves the reorganization of spin state populations and the decay of spin state coherences. In general, individual populations and coherences may exhibit different relaxation time constants. Particular spin configurations may exhibit exceptionally long relaxation time constants. Such spin configurations are known as long-lived spin order. The existence of long-lived spin order is a direct consequence of the symmetries of the system. For nuclear spin systems, rotational and permutational symmetries are of fundamental importance. Based on the Schur-Weyl duality theorem, we describe a theoretical framework for the study of rotational and permutational dual-symmetries in the context of long-lived spin order. Making use of the proposed formalism, we derive refined bounds on the number on long-lived spin populations and coherences for systems exhibiting rotational-permutational dual-symmetries.

Highlights

  • The term long-lived nuclear spin order refers to particular configurations of the spin ensemble that exhibit exceptionally long relaxation times

  • Spin configurations with exceptional lifetimes arise if the system exhibits a certain degree of symmetry

  • Not too surprising that the theory of long-lived nuclear spin order is most naturally formulated within a group of theoretical framework

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Summary

Bengs COLLECTIONS

ARTICLES YOU MAY BE INTERESTED IN Theory of long-lived nuclear spin states in methyl groups and quantum-rotor induced polarisation The Journal of Chemical Physics 142, 044506 (2015); https://doi.org/10.1063/1.4906273 Machine learning for interatomic potential models The Journal of Chemical Physics 152, 050902 (2020); https://doi.org/10.1063/1.5126336 Algorithmic cooling of nuclear spins using long-lived singlet order The Journal of Chemical Physics 152, 164201 (2020); https://doi.org/10.1063/5.0006742 Cite as: J. Chem. Phys. 152, 054106 (2020); doi: 10.1063/1.5140186 Submitted: 25 November 2019 • Accepted: 10 January 2020 • Published Online: 4 February 2020

INTRODUCTION
Groups and subgroups
Symmetric group
Dynamic groups
Conjugacy classes
Irreducible representations
Characters
Three-dimensional rotation group
Direct product groups
General framework
Rotational symmetries
Permutational symmetries
Schur–Weyl duality
Permutational symmetry
Odd number of spins
Even number of spins
SYSTEMS OF SPIN-1 PARTICLES
DUAL-SYMMETRY BASIS SETS
AN ILLUSTRATIVE NMR EXAMPLE
VIII. CONCLUSIONS
Dimensionality of Sn irreducible representations
Inner products
Dual-pairing in Liouville space
Spherical tensor operators
Methyl rotor correlation functions

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