▎ 摘　　要

Using the Hartree-Fock Su-Sheriffer-Heeger model and the sum-over-state method the linear and nonlinear polarizabilities, the dc Stark effect and the degenerate two-photon absorption (TPA) cross sections of the small-size trigonal zigzag graphene nanoflakes (TZGNs) have been investigated. The obtained dispersion spectra of the second-and third-order polarizabilities and the degenerate TPA cross sections of size-2 and size-3 TZGNs, which, respectively, have 22 carbon atoms with two edge states and 33 carbon atoms with three edge states, show peak values of the order of 10 (28) esu, 10 (32) esu and 10(3) GM, respectively. Furthermore, even-size TZGNs show electrostatic induced transparency due to their sizable dc Stark effect, which makes them suitable for linear and nonlinear optoelectronic devices.