How to train a magnet: Excitons as a new knob for magnetic control

Scientists can learn a lot about a quantum material by watching how it responds to light. In magnetic semiconductors, one especially useful messenger is the exciton: a pairing of a negatively charged electron and the positively charged “hole” it leaves behind.

Until now, excitons in magnetic materials have mostly been used as reporters. They could reveal how spins were arranged or how magnetic waves moved through a material. But Cornell researchers have shown that excitons can do more than observe magnetism. They can actively steer it.

In “Excitonic Spin Torque in a Magnetic Semiconductor,” published June 15 in Nature Materials, Youn Jue (Eunice) Bae, assistant professor of chemistry and chemical biology in the College of Arts and Sciences, and colleagues report that excitons created by light can exert a spin torque in the two-dimensional magnetic semiconductor chromium sulfide bromide, or CrSBr. The finding establishes excitons as a new way to control magnetic motion with light.

Read the full story in the Cornell College of Arts & Sciences website.

Researchers make moiré 2D materials without stacking, twisting

Cornell researchers have developed a new way to create moiré patterns – atomic-scale structures that can give materials unusual quantum behaviors – without relying on the difficult-to-control twisting and stacking methods traditionally used.

Moiré patterns arise when ultra-thin layers of materials are stacked slightly out of alignment, creating structural changes in atomic lattices that can alter how electrons move through a material. This can produce quantum behaviors such as correlated insulating states, magnetism and superconductivity.

But engineering moiré patterns has largely depended on manually rotating and stacking 2D flakes of materials, a process with limited reproducibility and scalability.

A new type of moiré engineering, published May 27 in the Proceedings of the National Academy of Sciences, uses a coating of thin films to apply controlled strain to layers of molybdenum disulfide, generating moiré superlattices across the material.

Read the full story in the Cornell Chronicle.

Quantum facility advances with $13.5M from Duffield Engineering

The buildout of a 10,000-square-foot quantum research facility at Cornell is advancing with a new $10 million investment from the Cornell Duffield College of Engineering, with an additional $3.5 million announced to support collaborative research projects.

The funding comes from a record-setting $371.5 million gift received from David Duffield ’62, MBA ’64, and builds on plans first unveiled in 2025 as part of an expansion and renovation of Duffield Hall. A key goal of the project is to establish a state-of-the-art, quantum-ready “collaboratory” space to support quantum engineering science and technology research and innovations. The new funding will equip the facility with instrumentation and technical expertise to fabricate quantum devices, among other capabilities.

Unlike traditional models in which university research labs are designed to support work by a single or small groups of investigators, Duffield Engineering’s “collaboratory” concept centers on a shared, multi-user facility that lowers barriers to entry into an emerging field for faculty and students across the college and university.

Read the full story in the Cornell Chronicle.