Quantum liquid versus electron solid around ν=1/5 Landau-level filling

In the high-magnetic-field low-disorder limit the ground state at {ν}=1/5 Landau-level filling is an incompressible quantum liquid. This is determined by observing vanishing resistivity ρₓₓ as the temperature T{→}0. At filling factors below {ν}=1/5 as well as in a narrow region above {ν}=1/5, ρₓₓ diverges exponentially as T{→}0. This contrasts the T dependence at any higher {ν}. We conclude that the quantum liquid at {ν}=1/5 is surrounded by a different phase. In as much as the exponential divergencies are indicative of an electron solid this phase is reentrant in a narrow region above {ν}=1/5.