Two phases, two rebuilding paths: MIT physicists watch electrons reassemble in erbium tritelluride

MIT physicists have captured something never seen before: two competing electronic phases inside a single material, rebuilding themselves in real time after being scrambled — and each phase heals through a completely different process. The discovery, published in Nature Physics on August 7, 2026, offers a new way to study the complex electronic behavior that underlies superconductivity and could guide the design of future quantum devices .

The material under the microscope is erbium tritelluride (ErTe₃), a rare-earth compound that, when cooled to very low temperatures, spontaneously develops two coexisting "charge density wave" (CDW) phases — orderly, wavelike patterns in which electrons organize themselves across the atomic lattice . These phases are not just a curiosity: many quantum materials, including high-temperature superconductors, host multiple competing electronic orders (such as magnetism and CDWs), and understanding how these orders interact is essential to controlling their behavior.

Two distinct rebuilding mechanisms

The MIT team, led by Nuh Gedik (the Donner Professor of Physics at MIT), used a "pump-probe" technique: they hit the ErTe₃ sample with an ultrafast laser pulse to momentarily disrupt both CDW phases, then watched with a second pulse how the electrons reorganized over time . What they saw was unexpected.

• The dominant CDW phase rebuilt uniformly and gradually — a classic, continuous (second-order) phase transition, analogous to liquid water evaporating into vapor .
• The subdominant (second) CDW phase rebuilt in a radically different way: electrons first formed isolated, nanometer-scale pockets of order, which then expanded and merged until the phase was fully restored. This nucleation-and-growth behavior — akin to water crystallizing into ice — had been theorized but never directly observed in this context .

The team used time- and angle-resolved photoemission spectroscopy (trARPES) to capture the electronic structure as it evolved on picosecond timescales, effectively creating a slow-motion movie of the rebuilding process .

Why this matters for superconductivity and quantum devices

The finding is more than a materials-science curiosity. Many of the most promising quantum materials — including those that host high-temperature superconductivity — exhibit multiple coexisting electronic phases. Untangling how these phases compete, coexist, and influence one another is a central challenge in the field .

• A new way to study competing orders: Because the two CDW phases in ErTe₃ rebuild through different mechanisms and on different timescales, researchers can now selectively study each phase by tracking its characteristic recovery signature. This provides a "very neat way to study these multiple phases," as co-author Alfred Zong noted .
• Toward switchable quantum devices: If engineers can selectively perturb one electronic order while leaving others intact, they may be able to switch a material between insulating, conducting, or superconducting states on demand — a core requirement for quantum logic and low-power electronics that go beyond silicon .
• A general experimental strategy: The pump-probe approach demonstrated in ErTe₃ is not limited to this one material. It can be extended to other quantum materials — including those relevant to topological quantum computing — to reveal hidden dynamics of competing orders that are invisible in equilibrium measurements .

Bottom line

This experiment shows that competing electronic phases in a quantum material can have fundamentally different formation mechanisms, and that these mechanisms can be disentangled simply by watching how the phases recover after a laser pulse. The approach gives physicists a powerful new tool to study the complex, cooperative behavior of electrons — and brings us one step closer to engineering materials with precisely controlled electronic properties.