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MemberSeptember 10, 2021 at 7:47 pm
To date, scientists have only been able to measure the energy and momentum of electrons at a material’s surface. To do so, they have used angle-resolved photoemission spectroscopy, or ARPES, a standard technique that employs light to excite electrons and make them jump out from a material’s surface. The ejected electrons are captured, and their energy and momentum are measured in a detector. Scientists can then use these measurements to calculate the energy and momentum of electrons within the rest of the material.
“[ARPES] is wonderful and has worked great for surfaces,” Ashoori says. “The problem is, there is no direct way of seeing these band structures within materials.”
In addition, ARPES cannot be used to visualize electron behavior in insulators — materials within which electric current does not flow freely. ARPES also does not work in a magnetic field, which can greatly alter electronic properties inside a material.
The technique developed by Ashoori’s team takes up where ARPES leaves off and enables scientists to observe electron energies and momenta beneath the surfaces of materials, including in insulators and under a magnetic field.
“These electronic systems by their nature exist underneath the surface, and we really want to understand them,” Ashoori says. “Now we are able to get these pictures which have never been created before.”