We have studied the magnetic order inside the superconducting phase of CeCoIn5 for fields along the [1 0 0] crystallographic direction using neutron diffraction. We find a spin-density wave order with an incommensurate modulation Q=(q,q,1/2) and q=0.45(1), which within our experimental uncertainty is indistinguishable from the spin-density wave found for fields applied along [1 -1 0]. The magnetic order is thus modulated along the lines of nodes of the d{x{2}-y{2}} superconducting order parameter, suggesting that it is driven by the electron nesting along the superconducting line nodes. We postulate that the onset of magnetic order leads to reconstruction of the superconducting gap function and a magnetically induced pair density wave.

Small-angle neutron scattering has been employed to study the influence of applied electric (E-)fields on the skyrmion lattice in the chiral lattice magnetoelectric Cu(2)OSeO(3). Using an experimental geometry with the E-field parallel to the [111] axis, and the magnetic field parallel to the [11(-)0] axis, we demonstrate that the effect of applying an E-field is to controllably rotate the skyrmion lattice around the magnetic field axis. Our results are an important first demonstration for a microscopic coupling between applied E-fields and the skyrmions in an insulator, and show that the general emergent properties of skyrmions may be tailored according to the properties of the host system.

We have investigated the magnetic structure in a polycrystalline sample of the B20-type MnGe by means of small-angle neutron scattering. On the projected diffraction plane normal to the incoming neutron beam, a Debye-ring-like pattern appears due to the random orientation of the spin helix q vectors (100). When an external magnetic field is applied normal to the incoming neutron beam, an intense peak with wave vector (q) perpendicular to the applied magnetic field is observed as the hallmark of the formation of a skyrmion lattice with a multiple-q helix in a wide temperature-magnetic-field region. This scattering intensity remains even after removing the magnetic field, which indicates that a skyrmion lattice is stabilized as the ground state. A different form of skyrmion lattice, either square or cubic, is proposed, which is also shown to be in good agreement with previous high-angle neutron diffraction results. Calculations based on such structures also describe the magnetic-field profile of the topological Hall resistivity.

The interplay of magnetic and charge fluctuations can lead to quantum phases with exceptional electronic properties. A case in point is magnetically-driven superconductivity 1,2 , where magnetic correlations fundamentally affect the underlying symmetry and generate new physical properties. The superconducting wave-function in most known magnetic superconductors does not break translational symmetry. However, it has been predicted that modulated triplet p-wave superconductivity occurs in singlet d -wave superconductors with spin-density wave (SDW) order 3,4 . Here we report evidence for the presence of a spatially inhomogeneous p-wave Cooper pair-density wave (PDW) in CeCoIn 5 . We show that the SDW domains can be switched completely by a tiny change of the magnetic field direction, which is naturally explained by the presence of triplet superconductivity. Further, the Q-phase emerges in a common magnetosuperconducting quantum critical point. The Q-phase of CeCoIn 5 thus represents an example where spatially modulated superconductivity is associated with SDW order.Superconductivity emerges in solids when electrons form Cooper pairs at low temperatures and condense in a macroscopically coherent quantum state, leading to zero-resistance and diamagnetism. For most phonon-mediated superconductors, the symmetry of the superconducting gap function is an isotropic singlet s-wave that does not break the symmetries of the underlying lattice. Unconventional superconductors 5,6 adopt more complex wave-functions: singlet d -wave in cuprates, extended s-wave for the pnictides and p-wave in ruthenates 7 . Although co-existing wave-functions are theoretically possible, most superconductors are adequately described by just a single wave-function. Here we provide evidence that p-wave superconductivity emerges in a d -wave superconductor and couples to a SDWforming a unique quantum phase with a spatially inhomogeneous superconducting Cooper pair-density wave.The stoichiometric heavy-fermion superconductor CeCoIn 5 serves as a model material for studies of d x 2 −y 2 -wave superconductivity 8,9 . It shares many properties with the cuprate superconductors, such as the zero-field superconducting wave-function 10-12 symmetry, a quasi-two-dimensional Fermi surface 13 and a spin resonance in the superconducting state 14 . Superconductivity emerges below T c (0) = 2.3 K and is Pauli-limited. The superconducting phase transition becomes first-order 15 close to H c2 (0), where SDW order has been observed that only exists in the Q-phase situated inside the superconducting phase [16][17][18] . The SDW propagation is pinned along the d x 2 −y 2 -line nodes, where low-energetic quasiparticles allow for electron nesting 17 (see Fig. 1a). In some microscopic theories addressing the nature of the Q-phase, the formation of a spatially modulated Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state plays a central role 19 . Other theoretical approaches emphasize SDW nesting 20,21 . Phenomenologically it has been shown 3,16 that SDW order in a d -wave super...