Quantum magnetic field sensors made of semimetal for light
Using a novel method they developed using quantum magnetic field sensors to visualise the flow of electricity, a team from Boston College found that the photocurrent flows in along one crystal axis of the Weyl semimetal and flows out along the perpendicular axis.
To visualise and understand the source of photocurrent flow in the semimetals, a team led by Boston College has developed a novel quantum sensor technique.
Brain Zhou, an assistant professor of physics at Boston College, and his colleagues have just discovered an unexpected new technique for employing quantum sensors to turn light into electricity in the semimetals. Their findings were published in the journal Nature Physics.
The conversion of light into electricity impulses is essential to the operation of many modern devices, including cameras, fibre optic networks, and solar panels.
Yet, because there is no clear direction for the flow of electricity in most materials, just illuminating light on their surface does not cause the creation of electricity.
https://phys.org/news/2023-01-team-quantum-sensors-reveal-weyl.html
Researchers are examining the special characteristics of electrons in the semimetals to get beyond these constraints and develop novel optoelectronic devices.
According to Zhou, who collaborated with two academics form the Nanyang Technological University Singapore and eight BC coworkers, the majority of photoelectric devices need the use of two distinct materials to produce an imbalance in space.
Here, he demonstrated how spontaneous photocurrents may arise from spatial asymmetry within a single material, particularly from asymmetry in tis thermoelectric transport capabilities.
The researchers investigated the semimetal known as tantalum iridium tetratelluride and tungsten ditelluride. Due to the fact that these materials’ crystal structures are naturally inversion asymmetric- that is they do not map onto themselves by reversing orientations around a point.
Why the semimetal is good at photocurrent production
Researchers have hypothesised that they might make suitable candidates for photocurrent production.
The goal of Zhou’s research team was to discover why Weyl semimetals are good at turning light into electricity. Similar to measuring the quantity of water flowing from a sink into a drainpipe, earlier measures could only quantify the amount of electricity leaving a gadget.
Zhou’s team attempted to visualise the electrical flow within the apparatus, much like creating a map of the whirling water currents in the washbasin, in order to better understand the source of the photocurrents.
Graduate student Yu-Wian Wang, the manuscript’s lead author, explained that as part of the project, they create a novel method using quantum magnetic field sensor.
It’s known as nitrogen-vacancy centres in diamond to image the local magnetic field generated by the photocurrents and reconstruct the complete streamlines of the photocurrent flow.
In the area where the light hit the material, the scientist discovered that the electrical current flowed in a four-fold vortex pattern. The researchers went on to illustrate flow pattern and found that the precise angle of the edge controls whether the device’s overall photocurrent is positive, negative, or zero.
They were able to explain the photocurrent generation process in terms of an anisotropic photo thermoelectric effect, or changes in how heat is converted to current along the distinct in plane directions of the semimetal, thanks to these previously unseen flow picture.
Interestingly, anisotropic thermopower may exist in different kinds of materials and is not always connected to the inversion asymmetry seen by the semimetals.
The discoveries provide a fresh avenue for the hunt for further highly photo responsive materials. It demonstrates the revolutionary effects of quantum-enabled sensors on unanswered issues in materials science.
Further efforts, Zhou will make use of the special photocurrent flow microscope to push the boundaries of detection sensitivity and spatial resolution as well as to comprehend the sources of photocurrents in other unusual materials.
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