Magnetic field dependence of the thermopower of Kondo-correlated quantum dots

Recent experiments have measured the signatures of the Kondo effect in the zero-field thermopower of strongly correlated quantum dots [Svilans et al., Phys. Rev. Lett. 121, 206801 (2018); Dutta et al., Nano Lett. 19, 506 (2019)]. They confirm the predicted Kondo-induced sign change in the thermopower, upon increasing the temperature through a gate-voltage dependent value T1≳TK, where TK is the Kondo temperature. Here, we use the numerical renormalization group (NRG) method to investigate the effect of a finite magnetic field B on the thermopower of such quantum dots. We show that, for fields B exceeding a gate-voltage dependent value B0, an additional sign change takes place in the Kondo regime at a temperature T0(B≥B0)>0 with T0