Bulk properties of the 5/2 fractional quantum Hall state with Corbino geometry

The nature of the ground state of the fractional quantum Hall (FQH) effects at half-filling in the second Landau level has been an interesting problem. In high-quality GaAs samples, the exact quantization of the 5/2 FQH state has been observed in van der Pauw geometry, but the fully bulk insulation of the 5/2 FQH state remains unrevealed. Corbino geometry, known for its edge-free nature, has been applied in studying the bulk physics of FQH states and charge density wave states recently. We will show our observation of bulk insulation in the 5/2 FQH state with Corbino geometry at an estimated low electron temperature of 12 mK. With in-plane electrical field, the stability of the 5/2 FQH state was explored. In our measurement, the 5/2 FQH state wasn’t enhanced by a weak in-plane electrical field as suggested. Our observation indicates a fully charge insulating nature of the bulk at filling factor 5/2 and could be informative for the proposed thermal conductivity measurements to search the striped Pfaffian and anti-Pfaffian state.