Microwave spectroscopy of the low-filling-factor bilayer electron solid in a wide quantum well

• Published in: Nature communications 2015-05, Vol.6 (1), p.7071-7071, Article 7071
• Main Authors: Hatke, A. T., Liu, Y., Engel, L. W., Shayegan, M., Pfeiffer, L. N., West, K. W., Baldwin, K. W.
• Format: Article
• Language: English
• Subjects: 639/766/119/1002; 639/766/119/2794; 639/766/25; Humanities and Social Sciences; multidisciplinary; Science; Science & Technology - Other Topics; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms8071

At the low Landau filling factor termination of the fractional quantum Hall effect series, two-dimensional electron systems exhibit an insulating phase that is understood as a form of pinned Wigner solid. Here we use microwave spectroscopy to probe the transition to the insulator for a wide quantum well sample that can support single-layer or bilayer states depending on its overall carrier density. We find that the insulator exhibits a resonance which is characteristic of a bilayer solid. The resonance also reveals a pair of transitions within the solid, which are not accessible to dc transport measurements. As density is biased deeper into the bilayer solid regime, the resonance grows in specific intensity, and the transitions within the insulator disappear. These behaviours are suggestive of a picture of the insulating phase as an emulsion of liquid and solid components. In 2D electron gases, insulating behaviour at low fractional quantum Hall filling factors is understood by the formation of an electronic Wigner solid. Here, the authors use microwave spectroscopy to evidence an electron liquid–solid mixed phase in bilayer states of GaAs/AlGaAs wide quantum wells.