Presence of chiral character in the spin resonance of the unconventional superconductor CeCoIn

重い電子系超伝導体CeCoInのスピン・レゾナンスに現れるカイラル項

Raymond, S.*; 金子 耕士   ; Hiess, A.*; Steffens, P.*; Lapertot, G.*

Raymond, S.*; Kaneko, Koji; Hiess, A.*; Steffens, P.*; Lapertot, G.*

In various unconventional superconductors, there exists characteristic magnetic response so-called "spin resonance". This mode is observed in inelastic neutron scattering below the superconducting transition temperature Tc at the wave vector for which the superconducting gap changes sign and at an energy 0.64. In order to get microscopic insights into the spin resonance, the heavy-fermion superconductor CeCoIn was investigated via polarized inelastic neutron scattering under a magnetic field. We found that the spin resonance at 0.6 meV at zero field splits under magnetic fields. The magnetic excitation under the field is characterized as two Zeeman split peaks with a chiral nature, and an additional non-chiral contribution that appears at the same energy as the lower mode of the Zeeman split peaks. This observation evidences that the spin resonance in CeCoIn is a degenerated mode, which has three fluctuation channels under magnetic field.