Cambridge, Massachusetts — 19 August 2026. Physicists at MIT have uncovered new details about how two distinct forms of electron organization emerge within the same quantum material, discovering that the two phases rebuild through fundamentally different mechanisms after being disrupted — one smoothly and uniformly, the other in expanding pockets resembling growing ice crystals. The findings, published in Nature Physics, could improve understanding of materials that display superconductivity, magnetism, and other exotic electronic properties.
The research, led by Nuh Gedik, the Donner Professor of Physics at MIT, focused on erbium tritelluride — a rare-earth material that supports two coexisting charge density wave (CDW) phases at low temperatures. By using precisely timed laser pulses to destroy the electronic order and then observe how it returns, the team identified the long-debated mechanism responsible for the emergence of the material's second electronic phase.
Charge Density Waves: A Simpler Playground for Complex Physics
A charge density wave develops when electric charges spontaneously organize into a repeating wave pattern. Regions corresponding to the crests contain more electrons, while the troughs contain fewer. In some materials, this coordinated state appears only at extremely low temperatures.
Physicists have studied charge density waves for decades. More recently, researchers have found them in materials that also support more complicated forms of collective electron behavior, including magnetism and superconductivity — the phenomenon where electrons pair together and move through a material without friction.
"Just like superconductivity, charge density waves are a collective phenomenon where electrons move together in certain ways," said Yifan Su, lead author of the study. "The power of CDWs is that they are a much simpler form of matter compared to superconductivity. They offer a playground for fundamental understanding."
The researchers chose erbium tritelluride specifically because it supports two different charge density waves simultaneously, providing a tractable system for studying how multiple electronic phases interact — a question with direct implications for understanding high-temperature superconductors and other complex quantum materials.
An Atomic Checkerboard of Electrons
Under ordinary conditions, electrons are distributed relatively evenly throughout erbium tritelluride. When the material is cooled, the electrons begin organizing themselves into wave-shaped arrangements.
The first, "dominant" charge density wave appears when erbium tritelluride is cooled to approximately −8 degrees Celsius, extending through the material in one direction. When the temperature drops further to approximately −113 degrees Celsius, a second "subdominant" charge density wave appears at a right angle to the first. Together, the two patterns form an atomic-scale checkerboard of coexisting electronic phases.
For the experiment, Gedik's team obtained atomically thin samples of erbium tritelluride created by collaborators at Stanford. They cooled the samples to roughly −230 degrees Celsius — cold enough for both charge density waves to exist simultaneously.
Shaking and Listening to Quantum Order
The researchers used two carefully timed laser pulses to study how the electronic phases form.
"This is how we 'shake' and then 'listen' to the system," Gedik explained.
The first laser pulse served as the "shake," breaking apart the electronic checkerboard. By varying the pulse intensity, the researchers could control how strongly they disrupted the charge density waves. A second pulse, containing high-energy photons, then knocked electrons out of the material. By applying this probe pulse at different intervals after the first and measuring the energy and momentum of the expelled electrons, the team captured a series of snapshots showing how the electronic phases recovered over time.
"We see the destroying of these phases, and then if we wait long enough, they come back," Gedik said. "And depending on how you hit them, the two phases respond differently."
Two Very Different Recovery Mechanisms
The results revealed a striking asymmetry in how the two phases rebuild.
The dominant charge density wave returned gradually and evenly, regardless of how strongly the researchers had initially disrupted the material. This smooth recovery corresponds to a textbook "second-order" phase transition — the same class of transition by which a magnet gradually loses its magnetism as temperature rises.
The second charge density wave behaved very differently. Instead of returning uniformly, the subdominant phase began forming in scattered pockets that expanded through the material — much like ice crystals growing through liquid water. This behavior corresponds to a less common "first-order" transition and was not what the researchers expected.
The observations allowed the team to identify the long-debated mechanism responsible for the emergence of the subdominant CDW phase — a question that had remained unresolved in the condensed matter physics community.
Implications Beyond Erbium Tritelluride
The findings have implications well beyond the specific material studied. More complicated quantum materials can contain several electronic phases simultaneously, and scientists suspect that the way those phases interact may be responsible for some of their most unusual properties.
"In systems that are much more complex, like high-temperature superconductors, you see there are multiple phases — magnetism, superconductivity, charge density waves, and they all exist together," Gedik said. "One of the theories is that the way they interact with each other is key for their exotic properties. The lessons we learn here can be applied to much more complex materials."
The research also highlights why understanding phase coexistence matters for practical applications. "People believe the cornerstone of replacing silicon lies in quantum materials that have multiple coexisting phases," said Alfred Zong PhD '20, co-author 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."
Research Support and Team
The study's other MIT co-authors include co-lead author Bai-Qing Lv, Dongsung Choi, Doron Azoury, and Masataka Mogi, along with collaborators from multiple institutions. The research was supported by the U.S. Department of Energy, the U.S. National Science Foundation, and the Gordon and Betty Moore Foundation's EPiQS Initiative.
The paper, "Time-domain identification of distinct mechanisms for competing charge density waves in a rare-earth tritelluride," was published in Nature Physics in 2026 (DOI: 10.1038/s41567-026-03382-5).
Sources
- MIT News, "Physicists watch materials' electrons assemble, reassemble in coexisting phases," 7 August 2026
- ScienceDaily, "MIT physicists discover electrons rebuilding like ice inside a quantum material," 19 August 2026
- Su, Y., Lv, B.Q., Zong, A. et al. "Time-domain identification of distinct mechanisms for competing charge density waves in a rare-earth tritelluride." Nature Physics (2026). DOI: 10.1038/s41567-026-03382-5
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