In a laboratory where a microscope can finally see individual atoms, physicists have built a model they long hoped to create: a lattice of fermions with three components rather than two, whose interactions can be dialed up or down. The work, carried out by a team spanning Germany, Thailand, India, China and the United States and reported in Science, offers a new window onto the strange collective behavior of matter that electrons in solids produce, and by extension onto questions as far apart as high-temperature superconductivity and the forces that bind quarks inside atomic nuclei. It is a re
Physicists Build Tunable Three-Component Hubbard System, Opening Path to Quantum Simulation of Nuclear Physics
Fears that three-body collisions would destroy the system did not come true
Mark
Why does a third component matter if the two-component model is still unsolved?
Mimi
Hazzard's argument is that adding a tunable third state shows how the two-component model responds, which could help with questions that have stayed open for decades.
Mark
And the link to nuclear physics?
Mimi
Three states resemble the three colors of quarks. It's not electrons on a lattice, but it echoes nuclear physics.
Luke
Echoes, though. The source says resembles, not reproduces. Quantum chromodynamics lattice models are a stated plan, not something done here.
Mark
What was the main worry going in?
Mimi
Three-body collisions destroying the system. Schauss said it turned out surprisingly stable, and they observed a Mott insulator.
Luke
Worth noting that's his characterization. The source doesn't give lifetimes or how long the system held together.
Mark
What about the other phases?
Mimi
Ferromagnetic correlations between two states and antiferromagnetic between two others, in the same system.
Luke
And the agreement with Rice's numerical calculations is on triple-occupied site counts specifically. It doesn't say the whole system is fully explained.
Mark
So what does it bear on for superconductivity?
Mimi
High-temperature superconductivity emerges near Mott states, so seeing one in this platform matters. But the source stops short of claiming any superconductivity result.
The Pulse
- A problem that theorists have wrestled with for decades meets a new tool: a three-component version of a model that until now existed only on paper.
- Experimenters feared that collisions among three atoms at once would tear the fragile system apart, yet the setup held steady long enough to be measured.
- A Mott insulator appears in the lab, where interactions freeze particles in place, and the same system displays both ferromagnetic and antiferromagnetic correlations.
- The team is now sharpening the interactions so the platform can mimic lattice models of quantum chromodynamics, with hopes of illuminating superconductivity along the way.
In a laboratory where a microscope can finally see individual atoms, physicists have built a model they long hoped to create: a lattice of fermions with three components rather than two, whose interactions can be dialed up or down. The work, carried out by a team spanning Germany, Thailand, India, China and the United States and reported in Science, offers a new window onto the strange collective behavior of matter that electrons in solids produce, and by extension onto questions as far apart as high-temperature superconductivity and the forces that bind quarks inside atomic nuclei. It is a reminder that understanding the deepest puzzles of nature often begins with building a simpler, controllable stand-in for them.
A quantum gas microscope, a device able to detect single atoms, has now been used to build something physicists have long wanted: a Hubbard model with three components instead of the usual two, and with interactions that can be tuned. An international team from Germany, Thailand, India, China and the United States reports the achievement in Science, calling it a first.
The Hubbard model is a central tool for describing how fermions move across a lattice. In ultracold-atom experiments, these atoms stand in for electrons in a solid, and the model is considered especially promising for understanding high-temperature superconductivity. Adding a third component opens room for richer quantum phases. The interactions are tunable because the energy shared by atoms on the same site depends on the magnetic field applied.
The experiment was led by Peter Schauss at the University of Hamburg. The team encoded three distinct fermion states in different internal states of the atoms, and the microscope tracked each atom individually. The goal was to observe a Mott state, where strong interactions block particles from flowing and the system turns insulating. Schauss admitted there was real risk, since three-body collisions could easily have destroyed the system. Instead, it proved surprisingly stable, and the Mott insulator was observed.
The researchers found more. The phases that appear depend on interaction strengths, and in one configuration the system showed ferromagnetic correlations between two states and antiferromagnetic correlations between two others. A method was also developed to count sites holding three atoms, and the results matched numerical calculations from collaborators at Rice University.
Kaden Hazzard of Rice noted that the Hubbard model is simple to write but hard to solve, and that the two-component version still leaves major questions open. A third tunable component, he suggested, may help answer them. The team plans to refine its interactions further, aiming to study lattice models of quantum chromodynamics in the laboratory.
A microscope that can see single atoms has now been used to watch a system that physicists have long wanted to build: a Hubbard model with three components instead of two, and with interactions that can be tuned. An international team from Germany, Thailand, India, China and the United States reports the result in Science, and describes it as a first.
The Hubbard model is one of the central tools for describing how fermions behave on a lattice. In ultracold-atom experiments, the fermionic atoms stand in for electrons in a solid, and the model is seen as especially promising for understanding high-temperature superconductivity. The standard version tracks two spin states, spin-up and spin-down. Adding a third component makes the system more versatile and lets researchers look for richer quantum phases.
The physics at the lattice level is simple to state. Atoms in the lowest energy state tunnel from one site to another, effectively swapping places. Identical fermions cannot share a location, but distinguishable ones can, and when they do, an interaction energy appears that depends on the magnetic field. That field dependence is what makes the interactions tunable.
The experiment was led by Peter Schauss, who works at the University of Hamburg and in the Cluster of Excellence "CUI: Advanced Imaging of Matter." The team used atoms in different internal states to realize different kinds of fermions, ending up with three distinct states. A quantum gas microscope detected each atom with spatial resolution. The result is very unlike electrons on a lattice, but it resembles nuclear physics, where quarks come in three colors.
Schauss said the team particularly wanted to see a Mott state, in which interactions suppress double occupation of sites. Strong interactions keep particles from flowing freely between sites, producing insulating behavior. Paradoxically, high-temperature superconductivity emerges near such Mott states. There was a real risk the attempt would fail. "Usually, one fears that three-body collisions could quickly destroy the system," Schauss said, but the realization proved surprisingly stable, and the team measured and observed a Mott insulator.
They found more than that. Which phases appear depends on the interaction strengths among the three states. In one case, the same system showed ferromagnetic correlations between two states and antiferromagnetic correlations between two others. The team also developed a way to determine how many lattice sites hold three atoms, and the measured values matched numerical calculations done by collaborators at Rice University.
Kaden Hazzard, an associate professor of physics and astronomy at Rice and a co-author, said the Hubbard model is simple to write down but hard to solve, and that theorists have struggled with the two-component version for decades with major questions still open. A third tunable component, he said, shows how the two-component model reacts and may help answer them. He and Sohail compared sophisticated numerical calculations with experiments already pushed to the limits of what is possible, and he expects those comparisons to help refine theoretical tools.
The researchers plan to refine the interactions in their model further so they can study lattice models of quantum chromodynamics in the laboratory. The work was funded by the National Science Foundation (PHY-1848304 and DGE-2346014), the Robert A. Welch Foundation (C-1872) and the W. M. Keck Foundation (995764).
Notable Quotes
Usually, one fears that three-body collisions could quickly destroy the system.— Peter Schauss, University of Hamburg
Adding a third tunable component lets us see how the two-component model reacts to it.— Kaden Hazzard, Rice University
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