Tunable spin-phonon polarons in a chiral molecular qubit framework

TL;DR

This paper provides the first experimental evidence of spin-phonon polarons in a chiral molecular qubit system, revealing tunable spin relaxation mechanisms that could enhance quantum information processing.

Contribution

It introduces a chiral molecular qubit framework demonstrating spin-phonon polarons and their impact on spin relaxation, a novel insight into chiral spin dynamics.

Findings

Observation of spin-phonon polarons through spin dynamic signatures.

Identification of a temperature-independent spin relaxation channel.

Demonstration of magnetic field and solvent effects on spin relaxation.

Abstract

Chiral structures that produce asymmetric spin-phonon coupling can theoretically generate spin-phonon polarons -- quasiparticles exhibiting non-degenerate spin states with phonon displacements. These quasiparticles are speculated to be the origin of chirality-induced spin selectivity and presumably can display exotic dynamic behaviors. However, direct experimental evidence of spin-phonon polarons has been lacking. Using a chiral molecular qubit framework embedding stable semiquinone-like radicals, we report spin dynamic signatures that indicate the formation of spin-phonon polarons for the first time. Our non-adiabatic model reveals that these quasiparticles introduce an active spin relaxation channel when polaron reorganization energy approaches Zeeman splitting. This new channel manifests itself as anomalous, temperature-independent spin relaxation, which can be suppressed by high magnetic fields or pore-filling solvents (e.g. CH2Cl2, CS2). Such field- and guest-tunable relaxation is unattainable in conventional spin systems. Harnessing this mechanism could boost repetition rates in spin-based quantum information technologies without compromising coherence or quantum sensing performance.