Theoretical analysis typically involves imaginary-time correlation functions. Inferring real-time dynamical response functions from this information is notoriously difficult. However, as we articulate here, it is straightforward to compute imaginary-time correlators from the measured frequency dependence of (real-time) response functions. In addition to facilitating comparison between theory and experiment, the proposed approach can be useful in extracting certain aspects of the (long-time relaxational) dynamics from a complex data set. We illustrate this with an analysis of the nematic response inferred from Raman scattering spectroscopy on the iron-based superconductor Ba(Fe1−xCox)2As2, which includes a new method for identifying a putative quantum critical contribution to that response.
@article{arxiv.1907.10182,
title = {Measuring the imaginary time dynamics of quantum materials},
author = {S. Lederer and D. Jost and T. Böhm and R. Hackl and E. Berg and S. Kivelson},
journal= {arXiv preprint arXiv:1907.10182},
year = {2020}
}