Song, YuTan, GuotaiZhang, ChenglinToft-Petersen, RasmusYu, RongDai, Pengcheng2018-11-092018-11-092018Song, Yu, Tan, Guotai, Zhang, Chenglin, et al.. "Unusual suppression of a spin resonance mode by magnetic field in underdoped NaFe1−xCoxAs: Evidence for orbital-selective pairing." <i>Physical Review B,</i> 98, no. 6 (2018) American Physical Society: https://doi.org/10.1103/PhysRevB.98.064507.https://hdl.handle.net/1911/103296We use inelastic neutron scattering to study the fate of the two spin resonance modes in underdoped superconducting NaFe1−xCoxAs(x=0.0175) under applied magnetic fields. While an in-plane magnetic field of B=12 T only modestly suppresses superconductivity and enhances static antiferromagnetic order, the two spin resonance modes display disparate responses. The spin resonance mode at higher energy is mildly suppressed, consistent with the field effect in other unconventional superconductors. The spin resonance mode at lower energy, on the other hand, is almost completely suppressed. Such dramatically different responses to applied magnetic field indicate distinct origins of the two spin resonance modes, resulting from the strongly orbital-selective nature of spin excitations and Cooper pairing in iron-based superconductors.engArticle is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.Journal articlePhysRevB.98.064507https://doi.org/10.1103/PhysRevB.98.064507