Understanding the geometric properties of quantum states is crucial in modern physics. The quantum geometric tensor (QGT) encodes information about a quantum state’s geometry, with its imaginary part being the Berry curvature, important for topological phenomena.
The fundamental part, the quantum metric, has recently gained attention for phenomena like anomalous Landau levels and flat-band superfluidity. However, experimental measurements of the QGT have thus far been limited to artificial two-level systems.
MIT physicists have measured the quantum geometry of electrons in solids for the first time. While the energies and velocities of electrons in crystalline materials have been studied, their quantum geometry was previously inferred or unknown. This breakthrough opens new possibilities for understanding and manipulating the quantum properties of materials.
The team has essentially developed a blueprint for obtaining new information that couldn’t be received before. The work could be applied to “any quantum material, not just the one the team worked with.
MIT physicists have trapped electrons in pure crystals
In quantum physics, electrons can be points and wave-like shapes described by a wave function. While simple wave functions are like balls, complex ones resemble structures like Mobius strips. Until recently, the quantum geometry of these wave functions could only be inferred.
MIT physicists solved this by using angle-resolved photoemission spectroscopy (ARPES) to measure the quantum geometry of wave functions in materials like kagome metals, which are crucial for quantum technology. This breakthrough opens new possibilities for quantum applications.
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, said, “The new ability to measure the quantum geometry of materials “comes from the close cooperation between theorists and experimentalists.”
“The COVID pandemic, too, had an impact. That facilitated a collaboration with theorists in South Korea.”
Journal Reference:
- Kang, M., Kim, S., Qian, Y. et al. Measurements of the quantum geometric tensor in solids. Nat. Phys. (2024). DOI: 10.1038/s41567-024-02678-8
