A glass of ice water offers a familiar example of two phases existing at the same time. The same substance can appear as both liquid water and solid ice. In certain quantum materials, different phases can also coexist, although the underlying behavior is far more complex.
MIT physicists have now uncovered new details about how two distinct forms of electron organization can emerge within the same quantum material. The findings, published in Nature Physics, could improve scientists' understanding of materials that display superconductivity, magnetism, and other electronic phases. Learning how these phases arise and interact could eventually help researchers gain greater control over electronic properties and develop more powerful quantum devices.
"People believe the cornerstone of replacing silicon lies in quantum materials that have multiple coexisting phases," says co-author Alfred Zong PhD '20, who co-led the study as an MIT graduate student and is now an assistant professor at Stanford University. "Our experiment provides a very neat way to study these multiple phases." The researchers, led by Nuh Gedik, the Donner Professor of Physics at MIT, investigated erbium tritelluride, a rare-earth material with unusual electronic behavior. Under ordinary conditions, electrons are distributed relatively evenly throughout erbium tritelluride.
When the material is cooled to specific temperatures, however, the electrons begin organizing themselves into a wave-shaped arrangement known as a "charge density wave" (CDW) phase. Cooling the material even further produces a second wave pattern running perpendicular to the first. Together, the two electronic phases form something resembling an atomic-scale checkerboard.
Gedik and his colleagues were able to separate the behavior of these two phases and observe how each one developed. The first phase appeared gradually across the material, somewhat like liquid water steadily becoming vapor. This matches the conventional picture of how many electronic phase transitions take place.
The second phase behaved very differently. Rather than appearing smoothly throughout the material, it began in isolated regions that expanded outward, resembling the way ice crystals begin forming in liquid water. "The mechanism responsible for the emergence of this second phase has long been debated, and our approach provides a powerful new way to uncover the hidden physics behind phase transitions in quantum materials," Gedik says.
Extract — continue reading at the source.
