Quantum Melting of a Disordered Wigner Solid

The behavior of two-dimensional electron gas (2DEG) in extreme couplinglimits are reasonably well-understood, but our understanding of intermediateregion remains limited. Strongly interacting electrons crystalize into a solidphase known as the Wigner crystal at very low densities, and these evolve to aFermi liquid at high densities. At intermediate densities, however, where theWigner crystal melts into a strongly correlated electron fluid that is poorlyunderstood partly due to a lack of microscopic probes for delicate quantumphases. Here we report the first imaging of a disordered Wigner solid and itsquantum densification and quantum melting behavior in a bilayer MoSe2 using anon-invasive scanning tunneling microscopy (STM) technique. We observe a Wignersolid with nanocrystalline domains pinned by local disorder at low holedensities. With slightly increasing electrostatic gate voltages, the holes areadded quantum mechanically during the densification of the disordered Wignersolid. As the hole density is increased above a threshold (p   5.7 * 10e12(cm-2)), the Wigner solid is observed to melt locally and create a mixed phasewhere solid and liquid regions coexist. With increasing density, the liquidregions gradually expand and form an apparent percolation network. Local soliddomains appear to be pinned and stabilized by local disorder over a range ofdensities. Our observations are consistent with a microemulsion picture ofWigner solid quantum melting where solid and liquid domains emergespontaneously and solid domains are pinned by local disorder.

Further reading#

• Access Paper in arXiv.org