Spirals in, harmonics out (IMAGE) DOE/SLAC National Accelerator Laboratory Caption Diagram of an experimental setup at SLAC’s high-power laser lab where scientists used circularly polarized laser light to probe a topological insulator – a type of quantum material that conducts electric current on its surfaces but not through its interior. A process called high harmonic generation shifts the laser light to higher energies and frequencies, or harmonics, as it passes through a TI. The harmonics allow scientists to clearly distinguish what electrons are doing in the material’s conductive surface and its insulating interior. Credit Shambhu Ghimire/Stanford PULSE Institute Usage Restrictions None License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.