Tuning the Two-Electron Hybridization and Spin States in Parallel-Coupled InAs Quantum Dots

We study spin transport in the one- and two-electron regimes of parallel-coupled double quantum dots (DQDs). The DQDs are formed in InAs nanowires by a combination of crystal-phase engineering and electrostatic gating, with an interdot tunnel coupling $t$ tunable by one order of magnitude. Large single-particle energy separations (up to 10 meV) and $|g^*|$-factor ($\sim$10) enable detailed studies of the $B$-field induced transition from singlet-to-triplet ground state as a function of $t$. In particular, we investigate how the magnitude of the spin-orbit induced singlet-triplet anticrossing depend on $t$. For cases of strong coupling, we find values of 230~$\mu$eV for the anticrossing using excited-state spectroscopy. Experimental results are reproduced by calculations based on rate equations and a DQD model including a single orbital in each dot.