MIT physicists have observed two competing electronic phases in a quantum material rebuilding themselves through distinctly different mechanisms, giving researchers a clearer way to study how complex phases emerge and interact in advanced materials.
The study, published in Nature Physics, focused on erbium tritelluride (ErTe3), a rare-earth material that forms two charge density wave phases as it cools. Charge density waves occur when electrons spontaneously organize into repeating patterns rather than remaining evenly distributed throughout a material. Researchers have long known that ErTe3 develops one charge density wave at about -8 degrees Celsius and a second, perpendicular wave at about -113 degrees Celsius. Together, the two patterns form a checkerboard-like arrangement. What remained less clear was whether the two phases formed through the same underlying mechanism.
Laser pulses reveal how phases recover
To investigate, the MIT-led team worked with atomically thin samples of ErTe3 synthesized by collaborators at Stanford University. Researchers cooled the samples to about -230 degrees Celsius, where both charge density waves are present, and then used laser pulses to disrupt the electronic order and track how it returned.
The first pulse disturbed or destroyed the existing charge density wave pattern. A second, higher-energy pulse ejected electrons from the material at controlled time intervals. By measuring the energy and momentum of those electrons using time- and angle-resolved photoemission spectroscopy, the researchers reconstructed how the two electronic phases recovered after excitation.
Two phases follow different transition pathways
The dominant charge density wave returned gradually and uniformly, consistent with a second-order phase transition. The secondary wave behaved differently. Instead of reforming smoothly across the sample, it first appeared in isolated regions that expanded over time, a nucleation-and-growth process characteristic of a first-order transition.
The findings provide experimental evidence for a mechanism that researchers have debated in studies of rare-earth tritellurides. The team also combined its spectroscopy measurements with time-dependent Ginzburg-Landau theory to establish a time-domain framework for distinguishing the mechanisms behind competing phases.
A new tool for studying complex quantum materials
For materials research labs, the significance extends beyond ErTe3. Quantum materials can host multiple electronic states, including charge density waves, magnetism, and superconductivity, and understanding how those states compete or coexist remains a central challenge in condensed-matter physics. The approach demonstrated in the study gives researchers another way to separate overlapping phase behavior and examine how individual states respond to controlled perturbations.
Nuh Gedik, professor of physics at MIT and senior author of the study, said insights from the work could be applied to more complex materials, including high-temperature superconductors. The researchers say the time-domain approach offers a broader framework for investigating phase transitions and competition in quantum materials.
This article was created with the assistance of Generative AI and has undergone editorial review before publishing.
