"Smoking gun" signatures of topological milestones in trivial materials by measurement finetuning and data postselection
Abstract
Exploring the topology of electronic bands is a way to realize new states of matter with possible implications for information technology. Because bands cannot always be observed directly, a central question is how to tell that a topological regime has been achieved. Experiments are often guided by a prediction of a unique signal or a pattern, called "the smoking gun". Examples include peaks in conductivity, microwave resonances, and shifts in interference fringes. However, many condensed matter experiments are performed on relatively small, micron or nanometerscale, specimens. These structures are in the socalled mesoscopic regime, between atomic and macroscopic physics, where phenomenology is particularly rich. In this paper, we demonstrate that the trivial effects of quantum confinement, quantum interference and charge dynamics in nanostructures can reproduce accepted smoking gun signatures of triplet supercurrents, Majorana modes, topological Josephson junctions and fractionalized particles. The examples we use correspond to milestones of topological quantum computing: qubit spectroscopy, fusion and braiding. None of the samples we use are in the topological regime. The smoking gun patterns are achieved by finetuning during data acquisition and by subsequent data selection to pick nonrepresentative examples out of a fluid multitude of similar patterns that do not generally fit the "smoking gun" designation. Building on this insight, we discuss ways that experimentalists can rigorously delineate between topological and nontopological effects, and the effects of finetuning by deeper analysis of larger volumes of data.
 Publication:

arXiv eprints
 Pub Date:
 September 2023
 DOI:
 10.48550/arXiv.2309.09368
 arXiv:
 arXiv:2309.09368
 Bibcode:
 2023arXiv230909368F
 Keywords:

 Condensed Matter  Mesoscale and Nanoscale Physics;
 Condensed Matter  Materials Science;
 Condensed Matter  Strongly Correlated Electrons;
 Condensed Matter  Superconductivity
 EPrint:
 Data are available through Zenodo at DOI: 10.5281/zenodo.8349309