Physicists Map Electron State Transition Between Solid and Liquid Quantum Phases

Researchers at Florida State University (FSU) have characterized a novel quantum phase where electrons dynamically shift between a rigid, crystalline solid state and an unconstrained, fluid-like movement. This finding, detailed in the journal npj Quantum Materials, documents an electron behavior that challenges existing paradigms in quantum mechanics.

The FSU team, which includes Cyprian Lewandowski, Hitesh Changlani, and Aman Kumar, validated their theoretical models using extensive computational resources, supported in part by the National Science Foundation's ACCESS program. The discovery builds upon the generalized Wigner crystal concept, first described by Eugene Wigner in 1934, which theorizes that electrons in two-dimensional systems can organize into ordered lattices under specific conditions.

The investigation revealed that by precisely tuning quantum interactions within a two-dimensional moiré superlattice, these ordered electron structures can undergo a "melting" transition into a liquid state. This contrasts with traditional Wigner crystals, which typically form only triangular lattices. The team also identified a hybrid intermediate state, termed the "quantum pinball" phase, where some electrons remain fixed in the lattice while others move chaotically. This mixed state simultaneously displays properties of both electrical insulation and conduction, representing an unobserved quantum mechanical effect.

To map these complex phase diagrams, the research group employed sophisticated analytical techniques, including exact diagonalization and Monte Carlo simulations, alongside density matrix renormalization group methods. The use of a two-dimensional moiré system enabled the observation of non-triangular crystalline shapes, such as stripes or honeycomb structures, within the generalized Wigner crystal, distinguishing it from the conventional Wigner crystal. Hitesh Changlani stated that the research focused on determining the exact energy scales required to trigger this specific phase transition.

This work offers a platform for probing many-body physics and quantum entanglement, providing a concrete model for investigating the interplay between Coulomb repulsion and kinetic energy that drives Wigner crystal formation. Observers suggest this breakthrough holds substantial weight for advancing quantum technologies, particularly in engineering robust qubits for fault-tolerant quantum computers. Furthermore, the capacity to actively tune these electron phases could accelerate developments in low-energy spintronics and enhance devices utilizing materials such as graphene. A key advantage noted is the potential to observe these phenomena without the stringent requirement of ultra-low cryogenic temperatures, opening pathways toward realizing room-temperature quantum effects.