QUANTUM LIQUID VERSUS ELECTRON SOLID AROUND V=1/5 LANDAU-LEVEL FILLING

In the high-magnetic-field low-disorder limit the ground state at =1/5 Landau-level filling is an incompressible quantum liquid. This is determined by observing vanishing resistivity xx as the temperature T0. At filling factors below =1/5 as well as in a narrow region above =1/5, xx diverges exponentially as T0. This contrasts the T dependence at any higher. We conclude that the quantum liquid at =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 =1/5. © 1990 The American Physical Society.