Imaging Correlated Electron States in Electrostatically Defined Quantum Dots

Strong Coulomb interactions in low-dimensional systems drive electrons to self-organize into spatially ordered states such as Wigner crystals in low-electron density 2D electron systems. Imposing further quantum confinement on such interacting systems causes new correlated states to emerge such as 0D Wigner molecules and 1D Zigzag Wigner crystals. Investigating how these correlated states evolve with confinement strength provides new insights into phase transitions and dimensional crossovers for interacting electron systems. We have used low-temperature scanning tunneling microscopy (STM) to create and probe in situ electrostatically defined 0D and 1D quantum dots (QDs) in bilayer MoSe₂. This approach enables direct visualization of interacting few-electron states in atomically clean and reconfigurable confinement potentials. In 0D QDs we observe the formation of few-electron Wigner molecules that undergo quantum melting with increasing carrier density. In 1D QDs we identify a transition from a linear 1D Wigner crystal to a zigzag Wigner crystal upon increased electron doping. These results show electrostatic QDs to be a versatile experimental platform for exploring correlated electronic behavior in low dimensions.