topological insulators – Lightsources.org

How the Advanced Light Source Is Accelerating Our Quantum Future

2026/08/262026/09/17

Key Takeaways

Quantum materials are key to advancing next-generation electronics, information technologies, and quantum computers.
For over 30 years, world-leading X-ray tools and experts at the ALS have helped researchers from all over the world investigate quantum materials such as superconductors, topological insulators, and correlated electron materials.
The Advanced Light Source Upgrade project will generate brighter beams of X-ray light, allowing researchers to push the boundaries of quantum materials research further by collecting data with far greater detail than has been possible before.

For more than three decades, the Advanced Light Source (ALS), a DOE Office of Science user facility at Lawrence Berkeley National Laboratory (Berkeley Lab), has helped scientists from all over the world advance their understanding of quantum materials — solids whose electrons interact so strongly with each other that entirely new collective behaviors such as superconductivity, exotic magnetism, and other phenomena emerge, defying the predictions of conventional theory.

The ALS is a leading third-generation synchrotron light source that specializes in soft X-ray and UV light instrumentation while providing researchers access to a full spectrum of X-ray light for scientific research. Through the years, powerful tools at the ALS have helped researchers from academia, the national labs, and industry identify and confirm the presence of quantum phenomena, leading to a number of significant advances, including early insights into graphene; the discovery of superconducting topological insulators; the development of a one-atom-thin magnet that could advance next-generation memory devices; new insight into the magnetic properties enabling read/write memory and memory storage devices; and a method for building qubits for quantum computers from 2D metal organic frameworks (MOFs).

Read more on the ALS website

Image: UC San Diego doctoral researchers Wei “Francis” He (far left), Kate Matthews (second from right), and Robin Glefke (far right) from the Alex Frañó group at the COSMIC Beamline (7.0.1) at the Advanced Light Source. They are working with ALS staff scientists Sujoy Roy (center) and Sophie Morley (second from left) to investigate the properties of a quantum material of interest for a neuromorphic system.

Credit: Robinson Kuntz/Berkeley Lab

Spin-Charge Conversion in Sb2Te3-based heterostructures

2025/06/242025/06/24

Spin-charge interconversion (SCIC) refers to the conversion of pure charge currents into pure spin currents and vice versa. These fundamental phenomena can be exploited to generate and manipulate electronic states for use in spin-based logic and memory devices. A wide variety of materials with high spin-orbit coupling, including topological insulators (TIs), are emerging as promising candidates for the implementation of SCIC devices. Although TIs are insulating in the bulk, they exhibit spin-polarized conductive electronic states localized on their surfaces. These states, known as topological surface states (TSSs), exhibit spin-momentum locking, meaning their spin and momentum directions are mutually orthogonal in reciprocal space. This property of TIs makes them particularly attractive for the design of efficient SCIC devices. TSSs are robust against nonmagnetic disorders, such as defects and impurities, but are disrupted by the proximity of magnetic materials, which are essential parts of SCIC device. To practically utilize TI in devices, it is necessary to devise a method to separate the TI from the magnetic material while keeping the TSS properties unaffected.

In this study, we explored Au and Al metals, which are widely used in the electronics industry, as spacer materials between a TI (Sb₂Te₃) and a magnetic (Co) film. Both materials have large spin diffusion lengths and, therefore, are suitable for supporting spin-polarized currents. Spin-pumped ferromagnetic resonance imaging (SP-FMR) studies showed that a high rate of spin-to-charge conversion is detected in a device based on the Sb₂Te₃/Au/Co heterostructure, while no conversion is observed when considering the Sb₂Te₃/Al/Co heterostructure.

To understand this difference in functional behavior, we analyzed the electronic and chemical properties of the interface between the TI and the Au and Al layers by performing angle-resolved photoemission spectroscopy (ARPES) experiments and core-level analysis at the high-resolution VUV-Photoemission beamline of Elettra. Au and Al were thermally evaporated under ultrahigh vacuum conditions onto in-situ exfoliated Sb₂Te₃ single crystals.

Read more on Elettra website

Ubiquitous formation of type-I and type-II bulk Dirac cones

2017/11/182018/03/12

… and topological surface states from a single orbital manifold in transition-metal dichalcogenides

Transition-metal dichalcogenides (TMDs) are renowned for their rich and varied properties. They range from metals and superconductorsto strongly spin-orbit-coupled semiconductors and charge-density-wave systems with their single-layer variants one of the most prominent current examples of two-dimensional materials beyond graphene.Their varied ground states largely depend on the transition metal d-electron-derived electronic states, on which the vast majority of attention has been concentrated to date.

>Read more on the Elettra website.

Image: Chalcogen-derived topological ladder in PdTe2.(a) Orbitally-resolved bulk electronic structure of PdTe2, indicating dominantly chalcogen-derived orbital character for the states in the vicinity of the Fermi level. (b) The measured out-of-plane dispersion together with the calculated band structure. Measured (c) and calculated (d) in-plane dispersion. (e,f) Spin-resolved energy distribution curves along the lines shown in (c).