Atomic-Resolution Electron Dichroism Opens a New Window into Quantum Materials
A research team led by Professor Wu Zhou from the School of Physical Sciences at the University of Chinese Academy of Sciences (UCAS), in collaboration with scientists from the Institute of Materials Science of Barcelona in Spain, the University of Washington in the United States, and Uppsala University in Sweden, has developed an atomic-resolution electron linear dichroism (ELD) technique based on scanning transmission electron microscopy (STEM). This method enables direct detection of orbital polarization at the level of individual atomic columns. The work, entitled "Detecting Linear Dichroism with Atomic Resolution," was published online in Nature Materials on May 12th, 2026.
Electronic orbitals govern many important properties of quantum materials, including magnetism, superconductivity, metal–insulator transitions, and interfacial charge transport. In many strongly correlated materials, electrons preferentially occupy orbitals pointing along specific crystallographic directions, producing “orbital polarization” that can drive symmetry breaking and emergent collective phases.
For decades, X-ray linear dichroism (XLD) has been one of the most powerful techniques for probing such orbital anisotropy. However, conventional XLD measurements average signals over micrometer-scale regions, making it impossible to directly resolve orbital variations associated with individual defects, interfaces, strain fields, or atomic-scale heterogeneities. Extending dichroic spectroscopy to true atomic resolution has therefore remained a longstanding challenge.
To overcome this limitation, the researchers developed a new STEM-based ELD methodology that combines atomic-resolution electron energy-loss spectroscopy (EELS) imaging with direction-selective momentum-transfer analysis. By precisely controlling the focused electron probe position and selectively extracting signals associated with orthogonal momentum-transfer directions, the method can distinguish between different orbital occupations within individual atomic columns.
The underlying principle originates from dipole-allowed inelastic scattering: momentum-transfer components oriented along different crystallographic directions preferentially couple to orbitals with different spatial symmetries. Using this directional sensitivity, the team successfully mapped anisotropic Mn 3d orbital occupation with atomic-column resolution.
Importantly, the technique does not require specialized hardware modifications and can be implemented on existing aberration-corrected STEM platforms using atomic-resolution EELS spectrum imaging acquired along a crystallographic zone axis. This greatly enhances its accessibility and potential impact across the electron microscopy community.
To validate the method experimentally, the team investigated epitaxial La0.7Sr0.3MnO3 (LSMO) thin films under different strain states. LSMO is a prototypical correlated oxide in which orbital polarization is known to strongly depend on lattice distortion.
The measurements revealed that compressive strain stabilizes preferential occupation of Mn 3d 3z²-r² orbitals, whereas tensile strain favors x²-y² occupation — fully consistent with previous macroscopic XLD studies, but now observed with single-atomic-column sensitivity. As a control experiment, no measurable ELD signal was detected in unstrained cubic SrTiO3, confirming that the technique specifically probes symmetry-breaking orbital anisotropy rather than generic structural contrast.
Figure 1. Atomic-scale electron linear dichroism (ELD) for probing orbital polarization and its experimental validation in strained perovskite manganite thin films.
Beyond manganites, the researchers believe the new methodology could provide a broadly applicable platform for studying orbital physics and symmetry breaking in a wide range of quantum materials and functional interfaces. Potential future applications include probing orbital reconstructions at oxide interfaces, electronic anisotropy near defects, low-dimensional quantum phases, and emergent states in superconducting and topological materials. The study also establishes a new bridge between electron microscopy and orbital spectroscopy by extending dichroic measurements from the micrometer scale down to the atomic scale.
Dr. Roger Guzman, formerly an research scientist at UCAS and now a tenured scientist at the Institute of Materials Science of Barcelona, is the first author of the paper. Professor Ján Rusz from Uppsala University provided the theoretical framework and dynamical diffraction calculations underlying the ELD signal analysis and signal extraction strategy. Professor Wu Zhou from UCAS's School of Physical Sciences, Professor Jaume Gazquez from the Institute of Materials Science of Barcelona, and Professor Juan Carlos Idrobo from the University of Washington are the corresponding authors. Ang Li, a doctoral student at UCAS, also contributed to the data analysis.
This research was supported by the Beijing Outstanding Young Scientist Program, the National Natural Science Foundation of China, the CAS Youth Team Program for Basic Research, and the Electron Microscopy Center at the University of Chinese Academy of Sciences.
Link to the research article: https://www.nature.com/articles/s41563-026-02606-6
Link to Prof. Wu Zhou’s group: https://zhouwu.ucas.ac.cn/
