Evidence of Coulomb liquid phase in few-electron droplets

Emergence of universal collective behaviour from interactions within a sufficiently large group of elementary constituents is a fundamental scientific concept¹. In physics, correlations in fluctuating microscopic observables can provide key information about collective states of matter, such as deconfined quark-gluon plasma in heavy-ion collisions² or expanding quantum degenerate gases^3,4. Mesoscopic colliders, through shot-noise measurements, have provided smoking-gun evidence on the nature of exotic electronic excitations such as fractional charges^5,6, levitons⁷ and anyon statistics⁸. Yet, bridging the gap between two-particle collisions and the emergence of collectivity⁹ as the number of interacting particles increases¹⁰ remains a challenging task at the microscopic level. Here we demonstrate all-body correlations in the partitioning of electron droplets containing up to N = 5 electrons, driven by a moving potential well through a Y-junction in a semiconductor device. Analysing the partitioning data using high-order multivariate cumulants and finite-size scaling towards the thermodynamic limit reveals distinctive fingerprints of a strongly correlated Coulomb liquid. These fingerprints agree well with a universal limit at which the partitioning of a droplet is predicted by a single collective variable. Our electron-droplet scattering experiments illustrate how coordinated behaviour emerges through interactions of only a few elementary constituents. Studying similar signatures in other physical platforms such as cold-atom simulators^4,11 or collections of anyonic excitations^8,12 may help identify emergence of exotic phases and, more broadly, advance understanding of matter engineering.