Nonlinear thermoelectric transport in a graphene with O-shaped Kekulé structure

The O-shaped Kekulé graphene, caused by lattice distortion, can be utilized in the study of thermoelectric effects due to its tunable bandgap. We adopted the tight-binding model in combination with the nonequilibrium Green’s function method investigate the thermoelectric transport properties of O-shaped Kekulé graphene structures in both linear and nonlinear regimes. The Seebeck coefficient S c , the thermoelectric figure of merit Z T and the power-generation efficiency η under different corresponding hopping energy modification parameter δ and perpendicular magnetic field are calculated. The calculation results show that, in the linear response region, with the coupling parameter δ set to zero, S c and Z T exhibit low values. These values are further diminished in the presence of a strong magnetic field. This performance is similar to the thermoelectric properties of perfect graphene. However, with the increase of coupling parameter δ , the thermoelectric coefficients ( S c , Z T ) rise significantly and further increases under the magnetic field. The thermoelectric properties of O-shaped Kekulé graphene can be adjusted by manipulating the magnetic field and modulating the coupling parameter δ . In the nolinear response region, firstly, when the temperature difference Δ T tends to 0, the equivalent figure of merit Z T M well returns to the Z T in the linear region, suggesting that our research methodology is reasonable and reliable. The perpendicular magnetic field applied to O-shaped Kekulé graphene strongly enhances Z T M and the efficiency η . It is shown that when η is greater than 33%, Z T M can still be greater than 15. The maximum values of the power-generation efficiency η and Z T M can reach by adjusting the hopping energy modification parameter δ and the magnetic field. The large Z T M value also maintains high power-generation efficiency, which indicates that the O-shaped Kekulé graphene has potential applications as thermoelectric devices. • We theoretically study the nonlinear thermoelectric transport of O-shaped Kekulé graphene under the perpendicular magnetic field by using the Landauer-Büttiker formula combined with the nonequilibrium Green’s function and find that the equivalent thermoelectric figure of merit ZT M of this setup has the large value and is easily regulated. • The magnetic field and coupling parameters δ have a very important effect on the nonlinear thermoelectric transport of O-shaped Kekulé graphene. • The ZT M in the nonlinear region degenerate to ZT in the linear region when the nonlinear temperature difference is very small ( Δ T → 0).