Chirality of the spin resonance in the unconventional superconductor CeCoIn
5investigated with polarized
neutrons under magnetic field
S. Raymond
1, K. Kaneko
2, A. Hiess
3, P. Steffens
4and G. Lapertot
11SPSMS, UMR-E 9001, CEA-INAC/UJF-Grenoble 1, 38054 Grenoble, France
2Quantum Beam Science Directorate, Japan Atomic Energy Agency, Japan
3European Spallation Source AB, 22100 Lund, Sweden
2Institut Laue Langevin, 38042 Grenoble, France E-Mail: arno.hiess@esss.se
In many unconventional (copper-oxide-, iron- or f-electron-based) superconductors a magnetic excitation is evidenced by inelastic neutron scattering (INS) below the superconducting transition temperature. This so-called spin resonance is visible at the wave- vector for which the superconducting gap, ∆, changes sign and for an energy Ωres/2∆ ≈ 0.64.
While there is no consensus on the origin of such an excitation and its relevance for the pairing mechanism, it provides important information relative to the symmetry of the superconducting state and it allows thus to reveal the nature of this state.
It is therefore important to get more microscopic insight into the spin resonance and in particular to investigate the multiplicity of this excited state. The application of a magnetic field may lift its degeneracy and polarized neutron scattering technique is very powerful to analyse the corresponding fluctuations. Among unconventional superconductors, f-electron based compounds with their intrinsic low characteristic energy scales are particularly suitable to observe strong effects under magnetic field. Resonance peaks are reported so far for the heavy fermion systems UPd2Al3, CeCu2Si2 and CeCoIn5.
Here we show by using polarized INS technique that the spin resonance in CeCoIn5 splits under magnetic field and that the magnetic response is composed of three channels: two Zeeman split peaks that have a chiral nature and a supplementary non-chiral contribution appearing at the same energy than the lower mode of the Zeeman split peaks.
