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The high-field/low temperature state of CeCoIn₅ (so-called Q-phase) is an intertwined d_x2-y2-wave superconducting order, a p-wave superconducting pair density wave (PDW), and a magnetically ordered spin-density-wave (SDW) [1]. When magnetic field is oriented within the a-b plane, the SDW ordering wave vector Q_SDW lies in one of the nodal directions of the

d_x2-y2-wave order parameter. We performed thermal conductivity measurement with magnetic field rotating within the a-b plane, both inside the intertwined phase (above 10 T) and a single d-wave SC phase (below 10 T) at low temperatures. The heat current was applied in the [100] direction of an anti-node of the superconducting order parameter. Above 7 T we observe a fine structure in thermal conductivity in rotating field, with multiple small oscillations in both phases. However, the phase of these oscillations changes by as much as π between the two states.  This can be understood in terms of the change of the topology of the Landau Fermi surface, as the SDW and the PDW gap nodes of the d_x2-y2 order parameter.

 [1] Duk Y. Kim et al., “Intertwined Orders in Heavy-Fermion Superconductor CeCoIn5”, Phys. Rev. X 6, 041059 (2016)