The world of quantum physics is mysterious. But what happens when that realm of subatomic particles is placed under immense pressure?<\/p>\n
A team led by physicists at Washington University in St. Louis has created quantum sensors that can survive in extreme conditions.<\/p>\n
Built inside unbreakable sheets of crystallized boron nitride, the devices can measure stress and magnetism in materials under pressure more than 30,000 times greater than the atmosphere.<\/p>\n
\u201cWe\u2019re the first ones to develop this sort of high-pressure sensor,\u201d said Chong Zu, assistant professor of physics in Arts & Sciences and member of the university\u2019s Center for Quantum Leaps.<\/p>\n
\u201cIt could have a wide range of applications in fields ranging from quantum technology, material science, to astronomy and geology.\u201d<\/p>\n
Sensors built from vacancy<\/p>\n
The work involved graduate students, postdoctoral researchers, and collaborating faculty members. <\/p>\n
Support came in part from a US National Science Foundation training grant, which funded six months of collaborative work at Harvard University.<\/p>\n
The team created the sensors using neutron radiation beams. These beams knocked boron atoms out of ultrathin sheets of boron nitride. The empty spots immediately trapped electrons.<\/p>\n
Those electrons, through quantum interactions, changed their spin depending on local magnetism, stress, or temperature. Tracking the spin revealed material properties at the quantum level.<\/p>\n
Zu\u2019s group had earlier built similar sensors in diamonds, which power WashU\u2019s two quantum diamond microscopes. <\/p>\n
Diamond sensors are effective but have limitations. Because diamonds are three-dimensional, the sensors cannot easily be placed close to the material under study.<\/p>\n
Boron nitride sheets solve this issue. They are extremely thin, less than 100 nanometers across, about 1,000 times thinner than a human hair.<\/p>\n
\u201cBecause the sensors are in a material that\u2019s essentially two-dimensional, there\u2019s less than a nanometer between the sensor and the material that it\u2019s measuring,\u201d Zu said.<\/p>\n
Diamonds continue to play a role. \u201cTo measure materials under high pressure, we need to put the material on a platform that won\u2019t break,\u201d explained graduate student Guanghui He.<\/p>\n
The group made \u201cdiamond anvils,\u201d small flat surfaces only 400 micrometers wide, to compress samples. \u201cThe easiest way to create high pressure is to apply great force over a small surface,\u201d He said.<\/p>\n
Tests confirmed the boron nitride sensors could detect subtle changes in the magnetic field of a two-dimensional magnet.<\/p>\n
The team now plans to test other materials, including rocks from high-pressure environments like Earth\u2019s core. <\/p>\n
\u201cMeasuring how these rocks respond to pressure could help us better understand earthquakes and other large-scale events,\u201d Zu said.<\/p>\n
The sensors may also shed light on superconductivity. Known superconductors require high pressure and extremely low temperatures. Controversial claims of room-temperature superconductors<\/a> remain unsettled.<\/p>\n \u201cWith this sort of sensor, we can collect the necessary data to end the debate,\u201d said graduate student Ruotian \u201cReginald\u201d Gong, a co-first author.<\/p>\n