Real-time Imaging Reveals Millisecond Dynamics of Non-trivial Defects in Electronic Wigner Crystals

The fleeting emergence of order from disorder underpins all complexity, and recent research focuses intensely on metastable states within quantum materials, though tracking their dynamic behaviour has proven challenging. Yevhenii Vaskivskyi, Jaka Vodeb, Igor Vaskivskyi, and Dragan Mihailovic, all from the Jozef Stefan Institute, now overcome this limitation by pioneering a fast-scanning tunnelling microscope technique to observe the internal dynamics of these defects in an electronic crystal. Their work reveals, for the first time, the millisecond-scale motion of individual electrons within these structures, demonstrating the behaviour of robust quasiparticles arising from complex interactions at a central junction. This observation of single-particle dynamics fundamentally alters our understanding of metastable quantum states and opens exciting possibilities for designing materials with engineered, topologically protected defects.

Equilibrium self-assembly underlies all emergent complexity, including life. In quantum materials, metastable states, which are not the lowest energy configuration but can persist for a measurable time, have become a prominent research topic. This work pioneers the application of fast-scanning tunnelling microscope techniques to investigate the internal dynamics of mesoscopic, metastable, topologically non-trivial defects within an electronic Wigner crystal superlattice, a structure created by locally perturbing the material’s surface. This approach enables the recording of unprecedented individual electron motion trajectories in real-time on the millisecond timescale, providing new insights into these complex dynamics.

Metastable States and Relaxation in 1T-TaS2

This research explores the complex behaviour of electrons in layered materials, specifically 1T-TaS2, focusing on emergent quantum states that arise from the collective behaviour of electrons. Scientists investigated how these metastable states relax towards equilibrium and the dynamics of charge density waves and domain walls. The team achieved real-time observation of several phenomena, including coherent transitions to metastable states and the reconfiguration of quantum domains, chiral domain dynamics, transient interference of mirrored superlattices, and the manipulation of fractionalized charge. These observations reveal the existence of emergent topological excitations, like domain walls, that exhibit unique behaviour and suggest the emergence of phases related to fractonic matter, a theoretical concept involving particles with restricted motion. The research also reveals low-frequency noise and fluctuations linked to the movement of domain walls or other defects, alongside a quantum jamming transition to a correlated electron glass state.

Electron Dynamics Visualized Within Quantum Crystal Structures

Scientists have achieved real-time observation of individual electron motion within a complex electronic crystal, revealing unprecedented details of metastable quantum states. Using fast-scanning tunnelling microscopy, the team recorded electron trajectories on the millisecond timescale within a Wigner crystal superlattice. This breakthrough allows direct visualization of how electrons behave in these normally hidden quantum environments. The research focused on a specific defect, a Y-junction vertex, formed within the electronic crystal. By applying an electrical pulse, scientists created a network of topologically non-trivial domain walls and vertices, enabling them to observe the dynamic behaviour of individual polarons, localized quasiparticles, at the junction.

Time-averaged images and extracted frames reveal quasi-periodic polaron motion, demonstrating persistent, sub-thermal fluctuations over several minutes. Analysis identified dislocations and disclinations associated with the moving polarons, revealing pentagon-heptagon pairs and single n-gon defects. Detailed analysis of temporal current fluctuations revealed two distinct types of noise behaviour: telegraph noise, indicative of particle motion, and featureless noise. Fourier power spectra revealed characteristic ‘flat-top’ Lorentzian curves in regions exhibiting telegraph noise, alongside 1/f noise elsewhere, demonstrating coherent phase relationships across the vertex.

Millisecond Electron Dynamics in Wigner Crystal Defects

This research pioneers a new method for observing the internal dynamics of metastable quantum states within electronic crystals. By employing fast-scanning tunnelling microscopy, scientists have, for the first time, recorded the motion of individual electrons on the millisecond timescale within topologically non-trivial defects created in a Wigner crystal superlattice. These observations reveal that the observed dynamics arise from the coupling of hybridised bound states with microscopic electronic degrees of freedom, leading to the formation of robust, localised quasiparticles. The team demonstrated that these quasiparticles exhibit remarkable stability, stemming from non-local constraints and broken symmetries within the system. This achievement fundamentally alters current understanding of metastable quantum states in electronic crystals and opens avenues for engineering materials with tailored topological defects.