Abstract
The ground state binding energy of a trion (X^-) is studied here. The trion is composed of two electrons and a hole, and is confined in a two-dimensional quantum dot in gapped graphene. We perform the study within the variational method using special trial wave functions with variational parameters, and discuss the effect of various variables, such as the quantum dot radius and the potential barrier height. Two types of quantum confinement are considered, namely, type I and type II. The estimated binding energy is -23.82 meV(with a Gaussian trial wave function) and -21.38 meV (with an exponential trial wave function), respectively, for a type I quantum dot with radius = 300 Å and barrier height = 0.375 Eg (Eg = band gap). For a type II quantum dot with radius = 300 Å and barrier height = 0.5 Eg, the estimated binding energy is -7.02 meV (with Gaussian function) and -8.02 meV (with exponential function), respectively. For fixed barrier height, the binding energy decreases as the quantum dot radius increases, eventually down to a limiting value. The study is relevant to the quantum state transfer between a photon qubit and a two-valley qubit in gapped graphene for a “graphene + photon” quantum network.