MIT Researchers Take a Big Step Toward Superconductivity

A major field of current research is in developing materials that exhibit exceptional electronic properties. In this field, the “holy grail” of discoveries is that of a room-temperature superconductor: a material that shows no electrical resistance and hence has no power loss. A room-temperature superconductor would allow for lossless power transmission over long distances, increasing efficiency and sustainability and decreasing the need for clunky cabling.

 

A special arrangement of atoms causes the electron state. Image used courtesy of MIT

 

While this has yet to be truly discovered, exploring electronic flat bands in materials has represented an intriguing path forward, especially for superconductivity and power electronics. Recently, physicists at the Massachusetts Institute of Technology (MIT) achieved a major step toward this goal by trapping electrons in a 3D crystal for the first time. 

 

Electron Trapping and Flat Bands 

To better understand the significance of this achievement, it is important to understand the concept of electron trapping and flat bands. 

Electrons, the negatively charged particles in atoms, typically move through conductive materials with varying energies, largely independent of each other. However, when electrons are confined to a material in a way that they occupy the same energy state, they enter a collective state known as an electronic flat band. In this state, electrons exhibit uniform energy levels across the band and can experience quantum effects more profoundly, leading to potentially exotic behaviors like superconductivity and unique forms of magnetism.

 

Electron trapping by excitation to the conduction band. Image used courtesy of Shoulders et al.

 

Previously, scientists have been able to trap electrons and confirm flat-band states in two-dimensional (2D) materials. However, maintaining these states in 2D has been challenging since electrons can easily escape from the plane, disrupting the flat-band state. Instead, the goal has been to replicate this in three-dimensional materials, where electrons can be confined in all directions, stabilizing these exotic states. 

However, this has been a significant challenge in the field, primarily due to the complex nature of 3D atomic structures and the difficulty in measuring electron energies in these materials.

 

The MIT Breakthrough 

In their recent research paper, researchers at MIT had a breakthrough with the world’s first successful trapping of an electron in a 3D state. 

The breakthrough involves trapping electrons in a pure crystal with a unique atomic arrangement inspired by the Japanese art of kagome basket weaving. This arrangement, a pyrochlore structure comprising a repeating pattern of cubes with faces resembling kagome lattices, effectively cages electrons within each cube, allowing them to settle into a flat energy band. The team synthesized a crystal of this structure using elements like calcium and nickel, creating a 3D material where electrons are trapped in all dimensions.

 

The Japanese kagome style of basket weaving inspired the structure of the 3D crystal. Image used courtesy of Okinawa Institute of Science and Technology

 

The researchers employed angle-resolved photoemission spectroscopy (ARPES) to confirm the flat-band state. This method allowed them to overcome the challenges posed by the uneven 3D surface of the material and precisely measure the energy of individual electrons. Their findings showed that the majority of the electrons in the crystal exhibited the same energy, confirming the flat-band state. Furthermore, altering the chemical composition (replacing nickel with elements like rhodium and ruthenium) could shift the electrons’ flat band to zero energy, leading to superconductivity.

 

A Huge Step for Material Science and Power Electronics

This research opens new avenues in material science, particularly for power electronics. The ability to trap electrons in 3D flat bands could lead to the development of materials with exceptional properties, like ultra-efficient conductivity or high-temperature superconductivity. High-temperature superconductors, or devices that operate with no electrical resistance at room temperature, can functionally enable lossless power transmission. These transmission cables would exhibit no impedances, allowing energy to be transported without power loss, creating significantly more efficient and environmentally friendly transmission. This could also reduce losses in electronic devices and advance quantum computing technologies. As research progresses, the implications of this discovery could lead to revolutionary changes in how power is generated, transmitted, and utilized, making it a critical development for the future of technology and sustainable energy solutions.