Electrons captured for the first time in a 3D crystal

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A true scientific achievement: For the first time, MIT physicists have captured electrons in a 3D crystal, creating a so-called “flat electronic band.” These advances, which modify traditional electronic dynamics, open perspectives for more viable superconducting materials. It promises potential applications in energy, quantum computing and electronic devices.

Quantum physics and materials science are taking another step forward with the recent breakthrough by researchers at the Massachusetts Institute of Technology (MIT). They managed to capture electrons in a three-dimensional crystal. They created what is called a ‘flat electronic band’.

In this state, all electrons share the same energy level and behave collectively rather than individually. The electrons are manipulated much more in this way. The results obtained by MIT researchers open the door to the exploration of superconductivity and other exotic electronic states in three-dimensional materials. The research has been published in the journal


Capturing electrons in a “Japanese basket”

Joseph Checkelsky’s team at MIT has achieved something extraordinary in the field of materials physics. The researchers synthesized a unique pyrochlore crystal in which they successfully trapped electrons in a so-called ‘flat’ state. This means that in this three-dimensional crystal all electrons are in a uniform energy state, instead of dispersed (different) energy levels, as is usually the case.

The structure of this crystal is inspired by the Japanese art of “kagome” basket weaving, a basket weaving pattern. More scientifically, in geometry this is called “trihexagonal tiling”. This particular structure creates a special atomic geometry that traps electrons, forcing them to occupy the same energy level.

An electron trap. © Checkelsky et al., 2023

Checkelsky explains in a press release MIT : “
It’s not much different from how nature makes crystals. We bring certain elements together – in this case calcium and nickel – melt them at very high temperatures, cool them and the atoms organize themselves into this kagome-like crystal configuration “.

The researchers then used angle-resolved photoemission spectroscopy (ARPES), an ultra-focused beam of light that can focus on specific locations on an uneven 3D surface and measure individual electronic energies at those locations. They found that the vast majority of electrons in the crystal had exactly the same energy, confirming the flat band state of the 3D material.

A uniform state of electrons that is not so rare…

Finally, the team transformed the crystal into a superconductor by changing its chemical composition and replacing the nickel with rhodium and ruthenium atoms. This change caused the electronic flat band to drop to a zero energy level, creating the ideal conditions for superconductivity.

You should know that traditionally the presence of flat tires is often considered a rare phenomenon and difficult to obtain. However, work by Checkelsky’s team shows that these can be a direct and intentional consequence of the way atoms are arranged in a material.

Riccardo Comin, one of the researchers involved, emphasizes that this progress changes our understanding of quantum materials. Instead of seeing flat tires as anomalies, they are now seen as features that can be designed and controlled. This means that scientists can now consciously design materials with flat bands, by adjusting the atomic arrangement, to take advantage of their unique properties.

Between opportunities and challenges

The ability to capture electrons in a planar 3D state therefore has major implications for several technological areas. First, these advances could make it possible to design superconducting materials to create materials that conduct electricity without resistance at higher temperatures than current superconductors. This means more efficient energy transmission systems, with less energy loss, which is crucial for sustainable and efficient energy use. When it comes to electronic devices, this technology paves the way for the creation of smaller, faster and more efficient electronic components.

It is clear that the opportunities in quantum computing are great. Remember that the idea with quantum computers is to use the quantum properties of particles, such as electrons, to perform calculations. Unlike classical computers that use bits (0 or 1), a quantum computer uses qubits, which can exist in multiple states at the same time thanks to quantum phenomena such as superposition. By trapping electrons in a crystal and creating planar electronic states, we can better control the quantum states of the electrons. This allows qubits to be manipulated more accurately and more stably.

However, this progress also brings technical challenges. One of the most important is the accurate measurement of electronic energies in these three-dimensional materials. Researchers must use advanced techniques such as angle-resolved photoemission spectroscopy (ARPES). This technique is complex, especially when applied to irregular surfaces, such as three-dimensional materials. Researchers must therefore develop and refine methods to overcome these technical obstacles so that they can fully realize the potential of these new superconducting materials.

Source: Nature

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