Uncertainty principle for experimental measurements: Fast versus slow probes

TL;DR

This paper explores how the timescale of experimental probes influences measurements in solid-state systems, revealing that different techniques can suggest contrasting phenomena due to fluctuation dynamics.

Contribution

It introduces a quantum mechanical framework linking measurement timescales to observed phenomena, resolving discrepancies among experimental results in complex materials.

Findings

Different experimental techniques probe different fluctuation timescales.

Fluctuation timescales can lead to seemingly contradictory ordering signals.

Reinterpretation of ordering phenomena based on fluctuation dynamics.

Abstract

The result of a physical measurement depends on the timescale of the experimental probe. In solid-state systems, this simple quantum mechanical principle has far-reaching consequences: the interplay of several degrees of freedom close to charge, spin or orbital instabilities combined with the disparity of the time scales associated to their fluctuations can lead to seemingly contradictory experimental findings. A particularly striking example is provided by systems of adatoms adsorbed on semiconductor surfaces where different experiments -- angle-resolved photoemission, scanning tunneling microscopy and core-level spectroscopy -- suggest different ordering phenomena. Using most recent first principles many-body techniques, we resolve this puzzle by invoking the time scales of fluctuations when approaching the different instabilities. These findings suggest a re-interpretation of ordering phenomena and their fluctuations in a wide class of solid-state systems ranging from organic materials to high-temperature superconducting cuprates.