Theory Meets Experiment in Low-Dimensional Structures with Correlated Electrons

Spin glasses are a fascinating but poorly understood magnetic state of matter, appearing in complex alloys like iron-based superconductors and magnetically-doped metals, like Mn-doped Cu. Intricately linked to spin frustration and disorder, spin glasses exhibit no long-range magnetic order upon cooling. Likewise, spin glasses exude the distinguishing phenomenon known as aging, where the magnetic state is dependent on the history of the material, unlike quantum spin liquids. Here we show a new type of non-collinear spin glass order, or so-called spin-Q glass, observable in elemental Nd(0001) in the absence of disorder. Using spin-polarized scanning tunneling microscopy down to mK temperature, we visualize the competing local non-collinear order at the atomic-scale and probe the subsequent aging phenomena in response to variable magnetic field and temperature. We relate the resultant glassy behavior to the crystalline symmetry, which leads to competing magnetic interactions. Results from ab initio calculations will also be discussed, as well as applications of the spin Q glass concept to potential brain-inspired hardware.