New Technique for Microwave Spectroscopy on Micron-Scale Materials

In recent years, interesting materials have emerged which are only available as micron-scale flakes whose GHz conductivity spectra are predicted to yield insights into their novel physics. These materials include twisted bilayer graphene, bilayer dichalcogenides, and artificial lattices for analog quantum simulations. For most current broadband GHz spectroscopy techniques, micron-scale flakes effect a signal that is too weak to be useful. We have developed a new broadband GHz spectroscopy technique that allows one to deduce both the excitation spectra and free carrier response of micron-scale flakes without requiring sophisticated sample preparation or measurement techniques.

 

We present results from proof-of-principle experiments conducted for micron-scale P⁺ monolayer regions encapsulated in Si, whose conductivity spectrum is expected to be constant in frequency for microwave frequencies. The results show excellent i) qualitative agreement with those expectations, and ii) excellent quantitative agreement with DC resistance measurements, indicating the ability to perform sensitive contact-free conductivity spectroscopy on µm-scale flakes. These theoretical results also show that P⁺ monolayers can support microwave applications, such as ESR in QIS.