[Paper Review] Helium-Cooled Cryogenic STEM Imaging and Ptychography for Atomic-Scale Study of Low-Temperature Phases

Noah Schnitzer, Mariana Palos+8 more|arXiv (Cornell University)|Mar 11, 2026

Advanced Electron Microscopy Techniques and Applications0 citations

TL;DR

Demonstrates atomic-resolution STEM imaging and multislice electron ptychography at liquid helium temperatures (~20–30 K) using a commercial helium-cooled holder, with rapid acquisition and careful registration to mitigate cryogenic instabilities.

ABSTRACT

Much of the exotic functionality of prime interest in quantum materials emerges from structural and electronic ground states that can only be accessed at cryogenic temperatures. Understanding device operation therefore requires structural characterization under the same low-temperature conditions at which these functional phases exist, as room-temperature measurements often probe a different structural state. Achieving atomic-resolution in scanning transmission electron microscopy imaging and particularly 4D-STEM electron ptychography at liquid helium temperature has remained extremely challenging because even small amounts of drift, vibration, and thermal instability associated with the cryogen can disrupt the stringent stability requirements of atomic-resolution STEM. In this work we demonstrate atomic-resolution STEM and multislice electron ptychography at temperatures as low as 20 K using a commercial helium cooled holder. We find that rapid scans and a multi-stage registration workflow are critical to reducing artifacts associated with cryogenic instability for atomic-resolution imaging, while for ptychography scan position correction including compensation for coupling between probe aberrations and position refinement is necessary for successful reconstructions. Together these results establish a pathway for reliable atomic-resolution STEM and ptychography at low temperature, enabling direct visualization of structural ground states relevant to quantum technology.

Motivation & Objective

• Enable atomic-resolution STEM imaging at cryogenic temperatures using a commercial helium-cooled holder.
• Demonstrate multislice electron ptychography (MEP) under liquid-helium conditions for low-SNR data.
• Identify and mitigate instability sources (drift, vibration, thermal drift) to enable reliable data acquisition at low temperature.
• Develop data acquisition and processing workflows, including registration and scan-position correction, suitable for low-temperature structural characterization of quantum materials.

Proposed method

• Use a side-entry cryogenic holder with external liquid helium dewar to achieve stable cooling.
• Collect rapid-frame ADF-STEM and BF-STEM images along with 4D-STEM datasets for MEP at 300 kV with a defined convergence angle.
• Apply rapid acquisition, register and average image stacks with rigid and non-rigid registration to reduce intra-frame distortions.
• Perform multislice electron ptychography using 4D-STEM data, with global affine scan-position initialization and per-point refinement during reconstruction.
• Model and compensate for probe aberrations (defocus and astigmatism) that couple to scan geometry to improve reconstruction convergence.
• Discuss limitations and propose improvements in hardware, detectors, and post-processing workflows for robust cryogenic ptychography.

Figure 1: Overview of the liquid helium atomic-resolution STEM experiment. Schematics of the (a) microscope optics and detectors and (b) sample holder, transfer line, and helium dewar illustrate the added instabilities in these conditions. The gray shaded region marks the vibration damping holder be

Experimental results

Research questions

• RQ1 Can atomic-resolution STEM imaging be achieved at liquid helium temperatures with a commercial helium-cooled holder?
• RQ2 Is multislice electron ptychography feasible under cryogenic helium cooling, and what corrections are needed for reliable reconstructions?
• RQ3 What are the dominant instability modes (drift, vibration, thermal fluctuations) affecting imaging at 20–40 K, and how can acquisition/processing mitigate them?
• RQ4 How do registration strategies (rigid vs non-rigid) impact image quality and artifact suppression in cryogenic imaging?
• RQ5 What role do probe aberrations play in ptychographic reconstructions under helium cooling and how can they be decoupled from scan corrections?

Key findings

• Atomic-resolution STEM imaging is achievable at temperatures as low as ~20 K using a helium-cooled holder.
• Rapid frame acquisition combined with robust registration can recover high-SNR images despite cryogenic instabilities.
• 4D-STEM multislice ptychography yields high-quality reconstructions when scan-position corrections account for coupling between probe aberrations and position refinement.
• Rigid registration with transitivity constraints substantially reduces misregistered shifts in distorted low-temperature datasets; non-rigid registration can improve but may introduce artifacts if not properly constrained.
• Aberration-coupled scan distortions (notably astigmatism combined with defocus) can bias ptychographic reconstructions unless probe parameters are jointly optimized.
• A pathway is established for reliable atomic-resolution STEM and ptychography at low temperatures, enabling direct visualization of low-temperature ground states relevant to quantum technologies.

Figure 2: Effects of thermal and mechanical instability on STEM imaging. (a) A cartoon visualization of the separation of instability in the system into large unidirectional drift associated with a temperature gradient along the holder rod (left) and the residual instabilities from the cryogen, room