Bhawana Jha, HFML Nijmegen, The Netherlands
Working in a high magnetic field facility is very exciting. With these powerful tools, you can reveal properties of matter that would otherwise remain hidden. For example, many researchers use Raman spectroscopy to study the electronic properties of graphene. But if you perform Raman experiments in high magnetic fields, you get much more information about the material because of the Landau level splitting of the energy levels. You may not only see the electronic properties in more detail, you also get a clear picture of various types of interactions going on in the graphene. In my PhD project I constructed a new experimental set-up for these measurements.
I combine Raman scattering and transport measurement techniques. This requires a special insert with an electrically contacted graphene sample on a chip carrier with a possibility to excite with a laser and detect the scattered light. It is very difficult to make this insert without damaging the sample. To prevent my hands from shaking, I even stopped drinking coffee at work. But the most important factor for these measurements is to have the cleanest possible graphene samples. This is still the biggest challenge for me. I can only perform experiments in high magnetic fields twice a year, when I get two weeks of magnet time. This forces you to think through every scenario in detail, prepare as much as you can beforehand and work very precisely.
Research can take unexpected twists. Last year, I established a new set-up to perform resonance Raman and resonance photoluminence experiments on semiconductors, and in the test phase my graphene was not ready yet. I took CdSe quantum dots and CdSe/CdS quantum rods from my supervisor and got amazing results: We could see all the fine structures very clearly in the first measurements, even at zero field. Fortunately, I got some extra weeks of magnet time to find out how magnetic fields influence the optical properties. During those weeks I did not get much sleep, I didn’t want to miss any minute of magnet time. Nobody had ever seen such high quality spectra for these quantum rods before! We are now working on two quantum rod publications.