Lithography Defined Semiconductor Moires with Anomalous In-Gap Quantum Hall states

We present our recent results from broadband optical spectroscopic investigations on Moiré superlattices (MSL) based on InAs quantum wells. An artificial MSL was created using interference lithography to pattern two artificial graphene (AG) layers with a twist angle of 5 degrees. Four samples were analyzed in the study: MSL 300/300/5, MSL 300/250/5, AG 300, and the substrate itself. Reflectivity spectra were obtained over a broad energy range from 15 meV up to 5 eV in a temperature range of 25-300K. All four samples exhibit minimal changes in the overall reflectivity with decreasing temperature; however, the phonons in the far infrared and the electronic transitions in the near infrared show a temperature-dependent red shifting. These changes in the reflectivity spectra correspond to the evolution of the band structure of this MSL device close to the Fermi level. The details of the observed excitations and their implications will be discussed in detail for each of the MSL samples.