Simulation of exchange coupling effects in double quantum dot FinFET-like structures
By leveraging a GPU-accelerated Schr\"odinger-Poisson (SP) solver, we characterize exchange coupling in a hole spin double-qubit device involving a double quantum dot (DQD) system formed inside a 5-gate silicon fin field-effect transistor (FinFET) similar to real experimental structures. The self-consistent SP simulations rely on a finite difference discretization of the 3D volume and on a Luttinger-Kohn 6x6 kp Hamiltonian accounting for magnetic fields and strain distribution. They return the gate-induced confined electronic states and the corresponding electrostatic potential hosting the DQD. These quantities serve as inputs to a two-particle Hamiltonian that is constructed from single-particle Slater determinants through the configuration interaction (CI) method. By diagonalizing this two-particle Hamiltonian, the eigenstates and eigenenergies of the DQD system are obtained, together with their exchange coupling. We show that our simulation framework, using a reduced number of basis states, is capable of reproducing the magneto-electrostatic behavior of the devices of interest, as predicted from theory and observed experimentally. We finally leverage our approach to determine the optimal operating conditions of a two-qubit quantum logic gate implemented in a Si FinFET structure.