Magnetic excitations of a new pressure-induced Kondo lattice superconductor

In unconventional superconductors such as heavy fermion and high-Tc superconductors, the superconductivity is believed to be mediated by spin fluctuations, rather than the electron-phonon pairing mechanism of conventional BCS theory. However, the microscopic mechanisms of spin-fluctuation mediated superconductivity are not yet determined, and in particular there is a lack of understanding as to which types of spin fluctuations are favourable for forming unconventional Cooper pairs. Here we propose to probe the low temperature magnetic excitations of single crystals of CeSb2 at ambient pressure using inelastic neutron scattering. CeSb2 is antiferromagnetic at ambient pressure, and was recently found to exhibit superconductivity under pressure upon the suppression of antiferromagnetism, with highly unusual behaviour of the upper critical field. We propose to map the spin-waves in the antiferromagnetic state, and paramagnons in the paramagnetic state, of CeSb2, so as to determine the underlying magnetic exchange interactions. Since these magnetic interactions give rise to both the ordered magnetic state at ambient pressure, and the unconventional, possibly spin-triplet, heavy fermion superconductivity under pressure, our study can provide important information about the characteristics of spin fluctuations giving rise to unconventional superconductivity.