Physicists at MIT have successfully trapped electrons in a pure crystal, achieving an electronic “flat band” in a three-dimensional material for the first time. This state allows electrons to behave in coordinated, quantum ways, potentially leading to superconductivity and unique forms of magnetism. The crystal’s atomic geometry, inspired by the Japanese art of basket-weaving known as “kagome”, enables this trapping of electrons. The researchers, including Joseph Checkelsky, Joshua Wakefield, Mingu Kang, Paul Neves, and Dongjin Oh, believe this discovery could lead to ultraefficient power lines, supercomputing quantum bits, and faster, smarter electronic devices.
Quantum Physics: Trapping Electrons in a Crystal
The researchers discovered that this flat-band state can be achieved with virtually any combination of atoms, as long as they are arranged in this kagome-inspired 3D geometry. This discovery provides a new avenue for scientists to explore rare electronic states in three-dimensional materials. These materials could potentially be optimised to enable ultra-efficient power lines, supercomputing quantum bits (qubits), and faster, smarter electronic devices.
The Kagome-Inspired Geometry
The atomic arrangement of the crystal, which resembles the Japanese art of “kagome,” was key to trapping the electrons. The researchers found that rather than jumping between atoms, electrons were “caged,” and settled into the same band of energy. This rare electronic state is thanks to a special cubic arrangement of atoms that resembles the Japanese art of “kagome.”
The researchers believe that this flat-band state can be realised with virtually any combination of atoms — as long as they are arranged in this kagome-inspired 3D geometry. This discovery provides a new way for scientists to explore rare electronic states in three-dimensional materials.
The Role of Pyrochlore in Trapping Electrons
The team of researchers looked to realise flat bands in 3D materials, such that electrons would be trapped in all three dimensions and any exotic electronic states could be more stably maintained. They found a certain geometric configuration of atoms, classified generally as a pyrochlore — a type of mineral with a highly symmetric atomic geometry. The pyrochlore’s 3D structure of atoms formed a repeating pattern of cubes, the face of each cube resembling a kagome-like lattice. They found that, in theory, this geometry could effectively trap electrons within each cube.
The Process of Synthesising a Pyrochlore Crystal
To test their hypothesis, the researchers synthesised a pyrochlore crystal in the lab. They combined certain elements — in this case, calcium and nickel — melted them at very high temperatures, cooled them down, and the atoms on their own arranged into this crystalline, kagome-like configuration. They then measured the energy of individual electrons in the crystal, to see if they indeed fell into the same flat band of energy.
The Potential of Superconductivity
The researchers also showed that they could transform the crystal into a superconductor — a material that conducts electricity with zero resistance. They found that when they synthesised a new crystal, with a slightly different combination of elements, in the same kagome-like 3D geometry, the crystal’s electrons exhibited a flat band, this time at superconducting states. This presents a new paradigm to think about how to find new and interesting quantum materials. The challenge now is to optimise to achieve the promise of flat-band materials, potentially to sustain superconductivity at higher temperatures.
“Now that we know we can make a flat band from this geometry, we have a big motivation to study other structures that might have other new physics that could be a platform for new technologies,” says study author Joseph Checkelsky, associate professor of physics.
“For this experiment, you typically require a very flat surface,” Comin explains. “But if you look at the surface of these 3D materials, they are like the Rocky Mountains, with a very corrugated landscape. Experiments on these materials are very challenging, and that is part of the reason no one has demonstrated that they host trapped electrons.”
“It’s like landing a helicopter on very small pads, all across this rocky landscape,” Comin says.
“This presents a new paradigm to think about how to find new and interesting quantum materials,” Comin says. “We showed that, with this special ingredient of this atomic arrangement that can trap electrons, we always find these flat bands. It’s not just a lucky strike. From this point on, the challenge is to optimize to achieve the promise of flat-band materials, potentially to sustain superconductivity at higher temperatures.”
Summary
Physicists at MIT have successfully trapped electrons in a pure crystal, creating an electronic “flat band” in a three-dimensional material for the first time. This achievement, which involves a special cubic arrangement of atoms, could pave the way for exploring rare electronic states in 3D materials, potentially leading to ultra-efficient power lines, supercomputing quantum bits, and faster, smarter electronic devices.
There is always much excitement around finding new superconducting materials; recently, a wave of interest turned out to be unfounded. Look at LK 99, for example, and recently retracted papers around the announcement of room temperature superconductors.
- Physicists at MIT have successfully trapped electrons in a pure crystal, achieving an electronic “flat band” in a three-dimensional material for the first time.
- The crystal’s atomic geometry, resembling the woven patterns in “kagome,” a Japanese art of basket-weaving, allows the electrons to be “caged” and settle into the same band of energy.
- The researchers believe this flat-band state can be achieved with any combination of atoms, as long as they are arranged in this kagome-inspired 3D geometry.
- This discovery could lead to the development of ultraefficient power lines, supercomputing quantum bits, and faster, smarter electronic devices.
- The study was led by Joseph Checkelsky, associate professor of physics at MIT, along with graduate students Joshua Wakefield, Mingu Kang, and Paul Neves, and postdoc Dongjin Oh, among others.
- The team also managed to transform the crystal into a superconductor, a material that conducts electricity with zero resistance, by chemically manipulating the crystal.
- The results of the study, published in Nature, provide a new way for scientists to explore rare electronic states in three-dimensional materials.
