New ‘Fire-and-Ice’ Phase of Matter Discovered in a Magnet

A newly discovered state of matter has emerged within a previously identified exotic phase in a magnetic compound.

In 2016, physicists Weiguo Yin, Christopher Roth, and Alexei Tsvelik from Brookhaven National Laboratory identified a unique “half-fire, half-ice” spin-state phase in Sr₃CuIrO₆, a compound of strontium, copper, iridium, and oxygen. Now, they have uncovered its opposite—a “half-ice, half-fire” phase, where electrons in two distinct structures swap behaviors.

At the core of this discovery is frustration, a concept describing how neighboring particles interact. A single change can trigger a cascading phase shift, reshaping the system. In the half-fire, half-ice phase, copper atom spins remain disordered, resembling flickering flames, while iridium spins stay frozen, strengthening their magnetic pull.

Mathematically, shifting this formation seemed impossible. However, the researchers identified a key temperature-dependent transition that flips the state entirely. This reversibility is a breakthrough, unlocking Sr₃CuIrO₆’s potential for quantum computing and microelectronics.

Unlocking Exotic States: A Path to Quantum Computing and Spintronics

“Finding new states with exotic properties—and understanding how to control their transitions—are fundamental challenges in condensed matter physics and materials science,” Yin explains. “Solving these problems could advance technologies like quantum computing and spintronics.”

Magnetic materials exist in different forms. In ferromagnets like iron, all particle spins align in the same direction. Ferrimagnets, like Sr₃CuIrO₆, contain two distinct spin states. The team’s 2024 research expands on their 2016 work, revealing that an external magnetic field can induce the half-fire, half-ice phase. In this state, copper spins become chaotic, while iridium spins align rigidly.

While intriguing, this phase alone offered little practical use. Qubits, the building blocks of quantum computing, rely on electron spin states to represent binary values. More importantly, tunable qubits—ones whose spins can be controlled—are highly desirable.

“Despite extensive research, we didn’t know how to utilize this state,” Tsvelik explains. “For over a century, the one-dimensional Ising model—a foundational mathematical model of ferromagnetism—was thought incapable of hosting a finite-temperature phase transition. We were missing key pieces of the puzzle.”

Unveiling the Hidden Twin: The Half-Ice, Half-Fire Phase Emerges

The missing piece was a hidden twin state. Within a narrow temperature range, the researchers found that copper spins become ordered while iridium spins fall into disorder, creating the half-ice, half-fire phase.

This discovery not only reveals a new class of hidden phases but also allows precise control over phase transitions, unlocking potential quantum applications. However, more work remains.

“Next, we’ll explore this fire-ice phenomenon in systems with quantum spins and additional lattice, charge, and orbital degrees of freedom,” Yin says. “New possibilities are now wide open.”

Read Original Article: Science Alert

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