In a significant advance for quantum physics, researchers have observed a synchronized rhythm in a rotating supersolid, an exotic state of matter that behaves as both a solid and a frictionless fluid simultaneously. This discovery challenges previous expectations of chaotic behavior in such systems and provides scientists with an unprecedented tool to investigate the strange dynamics of the quantum world. The highly ordered, self-organizing dance of quantum particles offers a direct window into the formation of quantum vortices, a key phenomenon in superfluids that has been difficult to measure directly until now.
The breakthrough deepens our understanding of matter under extreme conditions and opens new avenues for exploring complex quantum mechanics. A supersolid is a counterintuitive phase where atoms are locked into a rigid crystalline structure, like a solid, yet can flow through that very structure without any viscosity, a hallmark of a superfluid. By demonstrating that these bizarre structures can synchronize their motion when stirred, the research provides a powerful new method for studying quantum coherence and the emergence of collective behavior. Furthermore, these findings may have implications far beyond the laboratory, potentially offering an explanation for mysterious cosmic events observed in the universe’s densest objects, neutron stars.
A Paradoxical State of Matter
The concept of a supersolid has intrigued physicists for over 50 years. The idea that matter could simultaneously possess the properties of a rigid solid and a perfect fluid was once considered a fundamental paradox. Solids are defined by their ordered, crystalline lattice, where atoms are locked into fixed positions and resist deformation. Superfluids, on the other hand, are quantum liquids, typically formed at temperatures near absolute zero, characterized by zero viscosity and the ability to flow without losing energy. For decades, these two states of matter were believed to be mutually exclusive.
The theoretical possibility was first proposed in the 1960s, with physicists speculating that solid helium-4 might host such a phase, allowing some atoms to move through the crystal lattice without friction via quantum tunneling. However, conclusive experimental evidence remained elusive for many years. The modern breakthrough came with the use of ultracold atomic gases. Between 2021 and 2024, multiple research groups successfully created true supersolid states in laboratory settings. These experiments confirmed that atoms could self-organize into a rigid, repeating pattern while the entire system maintained the phase coherence and frictionless flow characteristic of a superfluid, turning a long-standing theoretical puzzle into an observable reality.
Creating a Quantum Crystal
Modern supersolids are not found in nature but are engineered in highly controlled laboratory environments. The process begins with a cloud of atoms, often from highly magnetic elements like dysprosium, which are cooled using lasers and magnetic fields to temperatures just fractions of a degree above absolute zero. At these extreme temperatures, the atoms enter a quantum state known as a Bose-Einstein condensate (BEC), where they lose their individual identities and behave like a single macroscopic quantum entity.
In this state, the intrinsic magnetic interactions between the atoms cause them to spontaneously arrange themselves into a series of distinct quantum droplets, forming a stable, repeating crystalline pattern. These droplets are held in a fixed structure, giving the substance its solid-like properties. At the same time, the entire collection of droplets is enveloped by a superfluid that allows particles to move without any resistance. This achievement gives physicists a stable platform to study the interplay between the two contradictory properties within a single, coherent quantum system.
Observing a Synchronized Dance
The most recent discovery came when researchers decided to stir this delicate quantum state. A team led by Francesca Ferlaino at the University of Innsbruck used magnetic fields to gently rotate their dysprosium atom supersolid. Based on classical physics and some quantum theories, they expected the ordered structure to break down into chaotic motion as the rotational force was applied. Instead, they observed something remarkable: the supersolid’s crystalline structure of quantum droplets snapped into a rhythmic, synchronized dance, harmonizing its rotation with the external stirring.
The Role of Quantum Vortices
This synchronized state provided a direct view into another hallmark of superfluids: the formation of quantum vortices. Unlike the single central whirlpool that forms in a stirred classical liquid like water, a rotating superfluid develops numerous tiny, discrete vortices, each spinning with an identical velocity. These vortices are a defining feature of quantum fluids but their direct observation has been a significant challenge. The synchronization of the supersolid crystal provided a new measurement tool. By tracking the system’s synchronized movement, the scientists could directly measure the appearance of these vortices, a critical aspect for understanding rotating quantum fluids.
From the Laboratory to the Cosmos
The implications of this research extend far beyond the lab, reaching into the realm of astrophysics. One of the most compelling applications is explaining the behavior of neutron stars. These are the incredibly dense collapsed cores of massive stars, and they are known to exhibit sudden, unexplained changes in their rotational speed, known as “glitches.” Current theories suggest that the interior of a neutron star may contain a superfluid core. The dynamics of vortices within this superfluid could be responsible for these abrupt glitches.
The experimental results from the supersolid provide a tangible model for these cosmic phenomena. By studying how vortices appear and behave in the synchronized supersolid, scientists can gain insights into the physical mechanisms that might be at play deep inside a neutron star. This research forges a powerful link between the microscopic quantum world that can be controlled in a laboratory and the macroscopic, astronomical universe, allowing supersolids to act as a unique window into the cosmos.
New Frontiers in Quantum Technology
While the primary impact of this discovery is on fundamental physics and astrophysics, it also opens doors for future quantum technologies. The ability to create and manipulate hybrid states of matter like supersolids is a crucial step toward developing more advanced quantum systems. The stable, coherent, and now predictable nature of these states makes them interesting candidates for quantum simulation, where they can model the behavior of other, less accessible quantum systems or even exotic particles.
In recent years, researchers have also succeeded in creating a supersolid state using light, known as a photonic supersolid. This development could have significant implications for quantum computing and communication. A photonic supersolid that combines the structural stability of a solid with the coherence of light could be an ideal medium for quantum memory, preserving qubit information, or for building ultra-stable optical components for use in lasers and quantum circuits. Although these applications remain on the horizon, the continued exploration of supersolids is blurring the line between light and matter and providing physicists with a versatile toolkit for designing the technologies of the future.