# Detecting Nematic Order in STM/STS Data with Artificial Intelligence

## TL;DR

This paper demonstrates that artificial neural networks can effectively detect nematic order in STM/STS data, even without sharp spectral features, by training on simulated data and applying to real experimental measurements.

## Contribution

The study introduces a supervised machine learning approach using neural networks to identify nematic order in STM data lacking clear spectral signatures, advancing detection methods in quantum materials.

## Key findings

- ANN successfully classifies simulated isotropic and anisotropic data.
- ANN predicts nematic order in experimental CaFe2As2 data with 99% confidence.
- Higher neural network complexity is required compared to traditional spectral feature detection.

## Abstract

Detecting the subtle yet phase defining features in Scanning Tunneling Microscopy and Spectroscopy data remains an important challenge in quantum materials. We meet the challenge of detecting nematic order from local density of states data with supervised machine learning and artificial neural networks for the difficult scenario without sharp features such as visible lattice Bragg peaks or Friedel oscillation signatures in the Fourier transform spectrum. We train the artificial neural networks to classify simulated data of isotropic and anisotropic two-dimensional metals in the presence of disorder. The supervised machine learning succeeds only with at least one hidden layer in the ANN architecture, demonstrating it is a higher level of complexity than nematic order detected from Bragg peaks which requires just two neurons. We apply the finalized ANN to experimental STM data on CaFe2As2, and it predicts nematic symmetry breaking with 99% confidence (probability 0.99), in agreement with previous analysis. Our results suggest ANNs could be a useful tool for the detection of nematic order in STM data and a variety of other forms of symmetry breaking.