quantum geometry in solid state physics

First Measurement of Quantum Geometry Marks a New Era in Quantum Physics

Introduction to Quantum Geometry in Solids

For the first time, MIT physicists and collaborators have directly measured the quantum-level geometry of electrons in solids. While the energies and velocities of electrons in crystalline materials are well-studied, their quantum geometry has previously been accessible only through theoretical inferences or remained unobservable.

Opening New Avenues in Quantum Physics

Riccardo Comin, MIT's Class of 1947 Career Development Associate Professor of Physics and lead researcher, describes the study, published in the November 25 issue of Nature Physics, as opening "new avenues for understanding and manipulating the quantum properties of materials."

A New Framework for Quantum Research

"We've effectively created a framework for accessing entirely new information that was previously unattainable," says Comin, who is also affiliated with MIT's Materials Research Laboratory and Research Laboratory of Electronics.

Broad Implications of the Research

Mingu Kang, the first author of the Nature Physics paper and a Kavli Postdoctoral Fellow at Cornell's Laboratory of Atomic and Solid State Physics, states that the research "has the potential to be applied to any type of quantum material, not just the one we studied." Kang, an MIT Ph.D. graduate (2023), conducted the work as a graduate student at MIT.

Kang's Contribution to the Research

Kang was invited to write a Research Briefing on the study and its implications, which was featured in the November 25 issue of Nature Physics.

An Uncanny World: The Wave Function in Quantum Physics

In the peculiar realm of quantum physics, an electron is described as both a localized point in space and a wave-like entity. Central to this work is a fundamental concept known as a wave function, which captures the letter. "You can imagine its as a surface within a three-dimensional space," explains Comin.

The Complexity of Wave Functions

Wave functions come in various forms, from the simple to the intricate. Imagine a ball—this represents a simple or trivial wave function. Now, envision a Mobius strip, a structure famously depicted by M.C. Escher in his artwork. This akin to a complex or non-trivial wave function. The quantum world is populated with materials made up of the latter.

Quantum Geometry: From Theory to Experiment

Until now, the quantum geometry of wave functions could only be inferred through theory, and in some cases, it wasn't understood at all. This property has become increasingly significant as physicists discover more quantum materials with potential applications, ranging from quantum computing to advanced electronic and magnetic devices.

ARPES: A Groundbreaking Technique

The MIT team addressed the issue using a method known as angle-resolved photoemission spectroscopy (ARPES). Comin, Kang, and their colleagues had previously employed this technique in other research. For instance, in 2022, they used ARPES to uncover the "secret sauce" behind the unique properties of a new quantum material called kagome metal. This work was also published in Nature Physics.

Assessing Quantum Geometry in Kagome Metal

In this study, the team modified ARPES to assess the quantum geometry of a kagome metal.

Intensive Partnerships and Collaboration

Kang  points out that the new skill to measure the quantum geometry of materials comes from the effective partnership between theorists and experimentalists.

The Impact of the COVID Pandemic on the Research

The COVID pandemic also played a role. Kang, originally from South Korea, was residing there during the pandemic. "This made it easier to collaborate with theorists in South Korea," says Kang, and experimentalist.

A Unique Opportunity for Comin

The pandemic also created a unique opportunity for Comin. He traveled to Italy to assist with ARPES experiments at the Italian Light Source Elettra, a national laboratory. Although the lab had been closed during the pandemic, it was beginning to reopen when Comin arrived.

Overcoming Challenges During the Pandemic

However, Comin found himself alone when Kang tested positive for COVID and was unable to join him. As a result, he ended up conducting the experiments on his own, with the support of local scientists.

A Personal Reflection from Comin

"As a professor, I oversee projects, but it is the students and postdocs who execute the work. This is essentially the final study where i was directly involved in the experiments," he explains.

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