Electron-nuclear spin control in charged semiconductor quantum dots by electrical currents through micro-coils

Abstract

We have fabricated micrometer-sized single-turn coils on top of charged CdSe/ZnSe quantum dot heterostructures by lithographical techniques. Current injection creates magnetic fields in the some 10 mT range, strong enough to modulate the hyperfine interaction. The very low coil inductance allows for generation of fast field transients. We demonstrate local control of the resident electron spin as well as read-out of the nuclear spin state on the 10 ns time scale by electrical current pulses.

Current‐induced control of the electron–nuclear spin system in semiconductors on a micrometer scale

“…Amplitude A versus field B z generated by a superconducting magnet (circles) and versus I coil in both current directions (up and down triangles) . .…”

“…It should be emphasized that the result in Fig. represents the situation for vanishing DNP, because the hyperfine interaction really equalizes the electron spin S and the average nuclear spin J , which in this case is zero due to the equally long pumping intervals and and the total cycle duration of only a few µs. In fact, the combination of optical and electrical pulses can be utilized to read‐out the nuclear spin state optically.…”

“…This can be achieved either by an effective magnetic field , such as, e.g., a magnetic exchange field , the spin–orbit field , and the Overhauser field or by a real external magnetic field, defined, e.g., by a microferromagnet prepared on top of the semiconductor or electrically generated by a microscale current loop . The latter approach permits a transient electrical spin control up to the GHz frequency regime and down to a micrometer length scale . Using millimeter‐sized external current loops, even the manipulation of single electron spins in individual quantum dots (QD) is achieved .…”

“…In the second type of experiments performed on CdSe/ZnSe QDs , the magnetic field of the microcoil is switched on and off on a sub‐ns time scale to decouple/couple the electron and nuclear spin systems, and to achieve an equalization of the electron spin with the average nuclear spin within the time scale of a single spin flip‐flop, respectively. The latter offers the unique possibility to read out the nuclear spin optically . In both experiments, we have achieved sub‐ns electrical control and fast optical read out of the semiconductor electron–nuclear spin system.…”

Optically detected nuclear magnetic resonance in n-GaAs using an on-chip microcoil

“…Different experimental methods have been developed to optically or electrically detect the NMR. 15 In this work, we adapt the on-chip microcoil technique to n-GaAs in order to perform NMR measurements on each species of isotopes in GaAs ͑ 69 Ga, 71 Ga, and 75 As͒ and to demonstrate Rabi oscillations of the 75 As nuclear spin ensemble on a spatial scale of below 5 m. Experimentally, an Overhauser field of B N ϳ 35 mT is generated via resonant excitation with circularly polarized light. 9,10 Quite often, the rf field needed for NMR is produced from a Helmholtz coil with a typical power consumption of ϳ100 W or so.…”