Magnetic field splitting of the spin-resonance in CeCoIn5

TL;DR

This study uses neutron scattering to demonstrate that the spin-resonance in superconducting CeCoIn5 splits into a Zeeman doublet under magnetic fields, revealing insights into its magnetic excitations and phase transitions.

Contribution

It provides the first direct observation of the Zeeman splitting of the spin-resonance in CeCoIn5, linking the Q-phase to a Bose condensate of spin excitons.

Findings

Spin-resonance in CeCoIn5 is a doublet that Zeeman splits under magnetic field.

The lower peak's energy extrapolates to zero at 11.2 T, near the Q-phase.

The Q-phase is likely a Bose condensate of spin excitons.

Abstract

Neutron scattering in strong magnetic fields is used to show the spin-resonance in superconducting CeCoIn5 (Tc=2.3 K) is a doublet. The underdamped resonance (\hbar \Gamma=0.069 \pm 0.019 meV) Zeeman splits into two modes at E_{\pm}=\hbar \Omega_{0}\pm g\mu_{B} \mu_{0}H with g=0.96 \pm 0.05. A linear extrapolation of the lower peak reaches zero energy at 11.2 \pm 0.5 T, near the critical field for the incommensurate "Q-phase" indicating that the Q-phase is a bose condensate of spin excitons.