Decoherence of a Hadamard basis state in three-spin system: The case of tunnel-couplings to semi-infinite graphene electrodes with armchair edges

We study the model of three-spin system consisting of a spin-1/2 quantum dot and two spin-1 particles. The three-spin system has two quantum states under the condition of isotropic exchange interaction, in which each of the states is corresponding to Bloch vector's pole and the control of these ones by the coherent manipulation yields another Hadamard basis state on the Bloch sphere. The purpose of this work is to clarify decoherence of a Hadamard basis state in the case that the system is tunnel -coupled to semi-infinite graphene electrodes with armchair edges. The results show that decay rate of a Hadamard basis state due to interaction with graphene electrodes is much smaller than that of metallic electrodes, and depends weakly on bias voltage. In addition, with the decrease of hybridization width, decoherence shows the transition from exponential decay to non-exponential one. Contrary to these features, decoherence of a Hadamard basis state undergoes the short-time dynamics for tunnel-couplings to zigzag edges.(c) 2022 Elsevier B.V. All rights reserved.