Kavli Affiliate: Feng Wang
| First 5 Authors: Zhehao Ge, Zhehao Ge, , ,
| Summary:
Electron Wigner solids (WSs)1-12 provide an ideal system for understanding
the competing effects of electron-electron and electron-disorder interactions,
a central unsolved problem in condensed matter physics. Progress in this topic
has been limited by a lack of single-defect-resolved experimental measurements
as well as accurate theoretical tools to enable realistic experiment-theory
comparison. Here we overcome these limitations by combining atomically-resolved
scanning tunneling microscopy (STM) with quantum Monte Carlo (QMC) simulation
of disordered 2D electron WSs. STM was used to image the electron density
($n_e$) dependent evolution of electron WSs in gate-tunable bilayer MoSe$_2$
devices with varying long-range ($n_mathrmLR$) and short-range
($n_mathrmSR$) disorder densities. These images were compared to QMC
simulations using realistic disorder maps extracted from experiment, thus
allowing the roles of different disorder types to be disentangled. We identify
two distinct physical regimes for disordered electron WSs that depend on the
magnitude of $n_mathrmSR$. For $n_mathrmSR lesssim n_e$ the WS behavior
is dominated by long-range disorder and features extensive mixed solid-liquid
phases, a new type of re-entrant melting-crystallization, and prominent Friedel
oscillations. In contrast, when $n_mathrmSR gg n_e$ these features are
suppressed and a more robust amorphous WS phase emerges that persists to higher
$n_e$, highlighting the importance of short-range disorder in this regime. Our
work establishes a new framework for studying disordered quantum solids via a
combined experimental-theoretical approach.
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