Imaging the Incipient Wigner electron lattice in a quantum wire

One-dimensional system abounds with physics especially considering electron-electron interaction. Electrons have been theoretically predicted to form a zigzag Wigner crystal when the electron density in a quantum wire approaches to specific magnitude. SO far such Wigner crystallization can only be inferred from conductance plateaus [1,2] and spatially resolved imaging of it remains a challenge. Here we utilize magnetic focusing technique[3] to probe the formation of a Wigner lattice, in which the spatial distribution of electrons in a quantum wire reveals itself in the magnetic focusing spectrum. Evolution from a focusing peak singlet to doublet --- in response to a one -dimensional single row transport to Wigner crystallization--- is shown when the density is continuously varied. Additionally, the focusing peak doublet is found to develop into a singlet with increasing temperature. [1] W. K. Hew \textit{et al.} Phys. Rev. Lett. 102, 056804 (2009). [2] L. W. Smith\textit{ et al. Phys. Rev. B} 80, 041306 (2009). [3] H. van Houten et al., Phys. Rev. B 39, 8556(1989).