Large transverse thermoelectric effect in graphene nanostructures

Thermal management in highly integrated chips and wearable devices is increasingly constrained by non-uniform heat flux distributions that resist both precise sensing and efficient energy recovery at the nanoscale. The transverse thermoelectric effect (TTE), in which the temperature gradient and the resulting thermoelectric voltage are spatially decoupled, offers a geometry-compatible route to on-chip heat sensing and harvesting, but prior implementations have required strong external magnetic fields or sub-liquid-nitrogen temperatures. Here we show a submicron graphene device that exhibits a transverse thermoelectric response at room temperature and zero magnetic field, which we term the ballistic transverse thermoelectric effect (BTTE). Enabled by asymmetric scattering of ballistic carriers, the device achieves a transverse Seebeck coefficient of 27.9 μV K−1, and a transverse thermoelectric power factor of ~35.8 μW cm−1 K−2. The transverse voltage retains its polarity upon reversal of the temperature gradient, enabling nanoscale heat-flow sensing and energy harvesting under spatially varying thermal conditions. The transverse thermoelectric effect (TTE) holds promise for on-chip heat sensing and harvesting, but it is usually limited by the need for magnetic fields or cryogenic temperatures. Here, the authors report the observation of TTE (with transverse Seebeck coefficient up to 27.9 μV K−1) in asymmetric graphene nanodevices operating at room temperature and zero magnetic field.