Contactless method tracks electrical flow in matter hotter than sun

Researchers have developed a groundbreaking contactless method to directly measure the electrical conductivity of warm dense matter—a state of matter hotter than the Sun’s surface found inside stars, giant planets, and Earth’s core. Traditional measurement techniques failed at these extreme temperatures because physical probes cannot withstand the heat. The new approach uses terahertz radiation to induce an electric field in a laser-heated aluminum sample heated to about 10,000 kelvin, allowing scientists to calculate conductivity without physical contact. This represents the most accurate measurement of conductivity in warm dense matter to date. The experiments revealed two unexpected sharp drops in aluminum’s conductivity as it transitioned from solid metal to warm dense matter and then to a disordered atomic state, confirmed by ultrafast electron diffraction capturing atomic-scale changes. This method opens new avenues for testing and refining theoretical models of matter under extreme conditions, which are crucial for understanding planetary magnetic fields and advancing nuclear fusion research. Although currently demonstrated only on aluminum, the researchers plan to extend the technique to more complex