Intertwined Spin and Orbital Density Waves in MnP Uncovered by Resonant Soft X-Ray Scattering

Abstract

Unconventional superconductors are often characterized by numerous competing and even intertwined orders in their phase diagrams. The fluctuations associated with these orders may provide the exotic pairing glue that underlies their high-temperature superconductivity. Helimagnet MnP, the first Mn-based superconductor under pressure, lacks high rotational symmetry. However, our resonant soft x-ray scattering experiment discovers novel helical orbital density wave (ODW) orders in MnP and reveals intertwined ordering phenomena. In particular, an ODW forms with half the period of the spin order and fully develops slightly above the spin ordering temperature, which resembles the behaviors of the nematic phase of the iron-based superconductors. Moreover, we find that their domains develop simultaneously, yet the spin order domains are larger than those of the ODW; and they cooperatively produce another ODW with 1/3 the period of the spin order. These observations provide a comprehensive picture of the intertwined orders in this three-dimensional, low-symmetry system and shed light on the understanding of its superconducting mechanism.