Tuning the two-electron hybridization and spin states in parallel-coupled InAs quantum dots

TL;DR

This paper investigates spin transport and singlet-triplet transitions in parallel-coupled InAs double quantum dots, demonstrating tunable interdot coupling and detailed analysis of spin-orbit effects through experimental and theoretical methods.

Contribution

It introduces a method to tune the two-electron hybridization and spin states in InAs quantum dots, providing new insights into spin-orbit interactions and singlet-triplet anticrossings.

Findings

Interdot tunnel coupling $t$ can be tuned by an order of magnitude.

Large energy separations up to 10 meV observed.

Singlet-triplet anticrossing energy of 230 μeV measured.

Abstract

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 $|g^*|$ factors ($\sim$10) enable detailed studies of the $B$-field-induced transition from a 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 depends 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.