Charge state readout and hyperfine interaction in a few-electron InGaAs double quantum dot

Abstract

A laterally defined InGaAs double quantum dot with an integrated charge readout sensor is realized in an InGaAs/InP heterostructure. The charge states of the double quantum dot are measured with the use of the charge readout sensor in the few-electron regime in which the current is too weak to be observable by direct measurements of electron transport through the double dot. We also measure the leakage current of the double quantum dot in the Pauli spin-blockade few-electron regime and study the singlet-triplet state mixing by the hyperfine coupling to the nuclear spins. The measurements of the leakage current in the weak external-magnetic-field region and for weak interdot couplings allow us to extract an effective nuclear magnetic field in the double-dot system. We also study spin relaxation and transport processes in the Pauli spin-blockade region at large external magnetic fields and observe transport through the excited triplet state in the few-electron double quantum dot.