1999/10/07 by Guido Burkard, Georg Seelig, Daniel Loss · 8 citations
Physics and Astronomy · #Condensed matter physics #Coulomb #Coupling (piping) #Electric field #Electron #Excited state #Magnetic field #Magnetic properties of thin films #Magnetization #Materials science #Physics #Quantum and electron transport phenomena #Quantum dot #Quantum mechanics #Semiconductor Quantum Structures and Devices #Singlet state #Spin (aerodynamics) #Spins #Zeeman effect #Zeeman energy #cond-mat.mes-hall
paper · pdf · doi:10.1103/physrevb.62.2581
published as Phys. Rev. B 62, 2581 (2000). · 13 pages, 9 figures
arxiv created 1999/10/07 · openalex publication_date 2000/07/15 · arxiv updated 2016/08/31 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We determine the spin-exchange coupling J between two electrons located in two vertically tunnel-coupled quantum dots, and its variation when magnetic (B) and electric (E) fields (both in-plane and perpendicular) are applied. We predict a strong decrease of J as the in-plane B field is increased, mainly due to orbital compression. Combined with the Zeeman splitting, this leads to a singlet-triplet crossing, which can be observed as a pronounced jump in the magnetization at in-plane fields of a few T, and perpendicular fields of the order of 10 T for typical self-assembled dots. We use harmonic potentials to model the confining of electrons, and calculate the exchange J using the Heitler-London and Hund-Mulliken techniques, including the long-range Coulomb interaction. With our results we provide experimental criteria for the distinction of singlet and triplet states, and therefore for microscopic spin measurements. In the case where dots of different sizes are coupled, we present a simple method to switch the spin coupling on and off with exponential sensitivity using an in-plane electric field. Switching the spin coupling is essential for quantum computation using electronic spins as qubits.