A team of Boston College scientists discovered that the photocurrent flows in (illustrated in blue) along one crystal axis of the Weyl semimetal and drains (shown in yellow/orange) along the perpendicular axis, represented here as an outcome of a brand-new technique the group developed utilizing quantum electromagnetic field sensing units to visualize the circulation of electricity. Credit: Zhou Lab, Boston College
A team led by Boston College has devised a brand-new quantum sensor technique to image and understand the source of photocurrent flow in Weyl semimetals.
In a recent paper released in the journal Nature Physics, Brian Zhou, an Assistant Professor of Physics at Boston College, and his colleagues have uncovered a surprising brand-new approach for transforming light into electrical energy in Weyl semimetals using quantum sensors.
Many modern innovations such as cams, fiber optic systems, and photovoltaic panels rely on the change of light into electrical signals. However, in the majority of products, merely shining light on their surface does not result in the generation of electricity as there is no particular instructions for the circulation of electrical energy. To conquer these restrictions and develop new optoelectronic devices, scientists are studying the unique residential or commercial properties of electrons in Weyl semimetals.
In the majority of materials, simply shining light on their surface area does not result in the generation of electrical energy as there is no particular instructions for the flow of electricity. Zhous research study group set out to understand why Weyl semimetals are effective at transforming light into electrical energy. Previous measurements might only determine the quantity of electrical power coming out of a device, like measuring how much water flows from a sink into a drainpipe. To much better understand the origin of the photocurrents, Zhous team sought to envision the circulation of electrical energy within the gadget– comparable to making a map of the swirling water currents in the sink.
” Most photoelectrical gadgets require two various materials to produce an asymmetry in space,” said Zhou, who dealt with 8 BC colleagues and 2 researchers from the Nanyang Technological University in Singapore. “Here, we revealed that the spatial asymmetry within a single product– in particular the asymmetry in its thermoelectric transport properties– can give increase to spontaneous photocurrents.”
The team studied the materials tungsten ditelluride and tantalum iridium tetratelluride, which both belong to the class of Weyl semimetals. Researchers have actually believed that these products would be excellent prospects for photocurrent generation because their crystal structure is inherently inversion asymmetric; that is to say, the crystal does not map onto itself by reversing instructions about a point.
Zhous research study group set out to comprehend why Weyl semimetals are effective at converting light into electrical energy. Previous measurements could just identify the amount of electricity coming out of a device, like determining how much water flows from a sink into a drain. To much better understand the origin of the photocurrents, Zhous group looked for to picture the flow of electrical energy within the gadget– similar to making a map of the swirling water currents in the sink.
” As part of the job, we established a brand-new method using quantum electromagnetic field sensors called nitrogen-vacancy centers in diamond to image the regional magnetic field produced by the photocurrents and reconstruct the full streamlines of the photocurrent flow,” graduate trainee Yu-Xuan Wang, lead author on the manuscript, said.
The team discovered the electrical existing flowed in a four-fold vortex pattern around where the light shined on the material. The team further visualized how the distributing circulation pattern is modified by the edges of the product and exposed that the precise angle of the edge identifies whether the total photocurrent flowing out of the device is favorable, negative, or absolutely no.
” These never-before-seen flow images permitted us to explain that the photocurrent generation mechanism is surprisingly due to an anisotropic photothermoelectric impact– that is to say, differences in how heat is transformed to existing along the different in-plane instructions of the Weyl semimetal,” Zhou stated.
Surprisingly, the look of anisotropic thermopower is not always related to the inversion asymmetry shown by Weyl semimetals, and hence, might be present in other classes of products.
” Our findings open a new direction for looking for other highly photoresponsive products,” Zhou stated. “It showcases the disruptive impact of quantum-enabled sensors on open questions in materials science.”
Zhou stated future projects will use the distinct photocurrent circulation microscopic lense to comprehend the origins of photocurrents in other unique products and to push the limits in detection level of sensitivity and spatial resolution.
Recommendation: “Visualization of bulk and edge photocurrent flow in anisotropic Weyl semimetals” by Yu-Xuan Wang, Xin-Yue Zhang, Chunhua Li, Xiaohan Yao, Ruihuan Duan, Thomas K. M. Graham, Zheng Liu, Fazel Tafti, David Broido, Ying Ran and Brian B. Zhou, 23 January 2023, Nature Physics.DOI: 10.1038/ s41567-022-01898-0.
The study was moneyed by the National Science Foundation, the DOE/US Department of Energy, and the Air Force Office of Scientific Research.