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 ((h) over bar Gamma = 0.069 +/- 0.019 meV) Zeeman splits into two modes at E(+/-) = (h) over bar Omega(0) +/- mu(B mu 0)H with alpha = 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. © 2012, American Physical Society.