title: Magnetic field splitting of the spin resonance in CeCoIn5.
abstract: Neutron scattering in strong magnetic fields is used to show the spin resonance in superconducting CeCoIn(5) (T(c)=2.3 K) is a doublet. The underdamped resonance (ħΓ=0.069±0.019 meV) Zeeman splits into two modes at E(±)=ħΩ(0)±αμ(B)μ(0)H with α=0.96±0.05. A linear extrapolation of the lower peak reaches zero energy at 11.2±0.5 T, near the critical field for the incommensurate "Q phase." Kenzelmann et al. [Science 321, 1652 (2008)] This, taken with the integrated weight and polarization of the low-energy mode (E(-)), indicates that the Q phase can be interpreted as a Bose condensate of spin excitons.
authors.affiliation: NIST Center for Neutron Research, 100 Bureau Drive, Gaithersburg, Maryland 20899, USA.
authors.forename: C
authors.initials: C
authors.lastname: Stock
authors.forename: C
authors.initials: C
authors.lastname: Broholm
authors.forename: Y
authors.initials: Y
authors.lastname: Zhao
authors.forename: F
authors.initials: F
authors.lastname: Demmel
authors.forename: H J
authors.initials: HJ
authors.lastname: Kang
authors.forename: K C
authors.initials: KC
authors.lastname: Rule
authors.forename: C
authors.initials: C
authors.lastname: Petrovic