Multiphoton Bloch-Siegert shifts and level-splittings in spin-one systems

TL;DR

This paper analyzes a spin-1 system coupled to an oscillator, revealing how multiphoton interactions cause level shifts and splittings, with a focus on resonance conditions at different excitation levels.

Contribution

It introduces a unitary transformation that separates Bloch-Siegert shifts from level splittings in a spin-1 system coupled to an oscillator.

Findings

Resonance can be maintained at high oscillator excitation levels.

Energy exchange affects level shifts at lower excitation levels.

An estimate for the critical excitation level is provided.

Abstract

We consider a spin-boson model in which a spin 1 system is coupled to an oscillator. A unitary transformation is applied which allows a separation of terms responsible for the Bloch-Siegert shift, and terms responsible for the level splittings at anticrossings associated with Bloch-Siegert resonances. When the oscillator is highly excited, the system can maintain resonance for sequential multiphoton transitions. At lower levels of excitation, resonance cannot be maintained because energy exchange with the oscillator changes the level shift. An estimate for the critical excitation level of the oscillator is developed.