At the RIKEN Center for Emergent Matter Science in Wako, Japan, physicists have just confirmed something theorists predicted but nobody had ever actually seen: an exotic thermoelectric trick hidden inside the semiconductor tellurium. Tetsuya Nomoto and Fumitaka Kagawa's team has experimentally demonstrated an unusual nonlinear thermoelectric effect—the kind of breakthrough that sounds abstract until you realize it could transform how we harvest energy from heat and manage thermal systems.
Most thermoelectric materials follow a straightforward rule: double the voltage, double the heat. It's linear, predictable, boring. But some special materials don't play by those rules. In chiral materials—where atoms or molecules are arranged in a mirror-image pattern, like left and right hands—theoretical physicists had long suspected something stranger should happen. Temperature differences combined with electric fields ought to generate voltage in unexpected directions, creating what amounts to an exotic variation of the Hall effect, the phenomenon where a current flowing through a conductor veers to the side when a magnetic field is applied perpendicular to it. The problem was nobody had ever caught this effect in action.
Until now. Nomoto, Kagawa, and their colleagues published their findings in Nature Physics, demonstrating that when you create a temperature difference across tellurium and apply an electric field at right angles to it, a voltage appears in a third perpendicular direction. It's called the nonlinear chiral thermoelectric Hall effect, and it works almost exactly as the theoretical predictions suggested it should.
What shocked the team most was the effect's strength. "We initially expected the signal to be extremely small," Nomoto recalls. Instead, they measured voltages of the order of microvolts—surprisingly large for such an exotic phenomenon—and the magnitude aligned remarkably well with recent theoretical calculations. This consistency between prediction and observation is the kind of thing that makes physicists genuinely excited.
The research wasn't easy. The team's decades of experience measuring heat transport in quantum materials, combined with their custom-built high-precision measurement systems, made this fiendishly difficult observation possible. Pulling off something this demanding required both technical mastery and the kind of institutional knowledge that only comes from years of working at the frontier of the field.
For now, Nomoto sees the practical applications as primarily laboratory-based: this effect could serve as a sensitive probe for investigating quantum geometric properties within materials or as a tool for determining whether a material is chiral. But that's where the work begins, not where it ends. Many questions remain unanswered—how does the effect change with temperature? What's happening at the microscopic level? Could other chiral materials beyond tellurium exhibit similar or even more dramatic effects?
The team is already planning follow-up studies. Nomoto intends to extend measurements to chiral materials beyond tellurium, gradually building a deeper understanding of this nonlinear chiral thermoelectric phenomenon. These are the kinds of incremental advances that sometimes lead somewhere extraordinary. For now, it's enough that something predicted by theory has finally stepped out of equations and into the real world.