Transport of a sliding Wigner crystal in the four flux composite fermion regime

In two-dimensional (2D) electron systems, Wigner crystals (WC) and fractional quantum Hall effect (FQHE) liquids are competing ground states under low temperatures $(T)$ and high magnetic fields $(B)$. Here we report differential conductivity results demonstrating the reentrant insulating phase around $\ensuremath{\nu}=1$/5 in a 2D hole system in AlGaAs/GaAs quantum wells and unexpected features in the solid-liquid phase transition between WC and FQHE liquids in ultrahigh magnetic fields up to 45 T. Remarkably, the electric field $(E)$ plays an equivalent role as the temperature does in our phase diagram. From the $E\ensuremath{-}T$ ``duality'' analysis, a characteristic length of 450 nm is derived, which can be understood as the phase-coherent domain size of WC. Moreover, evidence shows that with weak disorder the insulating phase and composite fermion liquid could be coexisting around $\ensuremath{\nu}=$ 1/5, pointing to the possibility that the insulating phase is the four flux quantum Wigner crystal, as proposed by theories.