Novel Multi-modal Spectroscopy Probe of Emergent Quanutm Order in Materials

Determining phases of quantum materials of many-body systems is oftentimes elusive because conventional probes cannot resolve contributions from multiple interconnected degrees of freedom (DOF). For instance, bulk thermodynamic measurements have a hard time distinguishing which phase contributes the most to the corresponding symmetry breaking because, in principle, different phases can be associated with the same symmetry breaking. On the other hand, complex multipolar orderings can create "invisible" local observables whose signatures are washed out in conventional experiments sensitive to only one characteristic of the emergent phase.

Here, we describe our novel approach to probe quantum states of matter by monitoring the net quantum phase accumulated during the controlled nuclear spin-ensemble time-evolution under the influence of the relevant local microscopic electronic Hamiltonian. Complex radio-frequency pulse sequences serve to selectively control decoherence from different parameters in the Hamiltonian, allowing us to independently distinguish their type (e.g., spin, charge, and/or orbital) and measure their relative strength together with their distribution/noise. Specifically, we discuss how this spin-based, multi-modal technique can quantify the inversion symmetric and inversion asymmetric interactions in the presence of strong magnetic noise. it allows for identifying the presence of these interactions and their fluctuations, even for a zero-mean value. We showcase the application of this technique on a strongly correlated material, a Mott insulator with strong spin-orbit coupling, where we distinguish between charge and spin DOFs.



- PRB 108, 054421