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18/06/2024 - Age: 25 days

New excitations discovered spin glasses

Zero-energy droplets provide intermediate picture

The energetics and geometry of low-temperature excitations are one of the fundamental characteristics of the spin-glass phase.

In a recent paper in Physical Review Letters with colleagues from Harvard University, Washington University St. Louis and Indiana University, we discuss a new type of excitations that occurs when a single exchange coupling is tuned from very negative to very positive. At a critical coupling value, a unique "critical" cluster of spins flip. As we investigate in detail, the average volumes and boundaries of these clusters diverge with system size. At the same time, their energy is strictly bounded from above and does not scale with system size. In terms of geometry, such droplets are compact, but feature a fractal boundary. They are hence perfectly intermediate between the expensive excitations of the droplet model with their fractal boundaries and the O(1) energies of excitations in the replica-symmetry breaking approach that come with space-filling domain walls.