Conservation of Angular Momentum in the Elastic Medium with Spins

TL;DR

This paper demonstrates that angular momentum conservation in elastic media with spins requires anharmonicity, leading to multiphonon processes and unique spin transition dynamics relevant for solid-state qubits.

Contribution

It reveals the essential role of anharmonicity in conserving angular momentum and its implications for spin-lattice interactions and quantum information applications.

Findings

Angular momentum conservation necessitates anharmonicity in elastic media.

Spin transitions involve multiphonon processes unlike atomic transitions.

Implications for solid-state qubits and quantum information processing.

Abstract

Exact conservation of the angular momentum is worked out for an elastic medium with spins. The intrinsic anharmonicity of the elastic theory is shown to be crucial for conserving the total momentum. As a result, any spin-lattice dynamics inevitably involves multiphonon processes and interaction between phonons. This makes transitions between spin states in a solid fundamentally different from transitions between atomic states in vacuum governed by linear electrodynamics. Consequences for using solid-state spins as qubits are discussed.