Detection of single electron spin resonance in a double quantum dot

Abstract

Spin-dependent transport measurements through a double quantum dot are a valuable tool for detecting both the coherent evolution of the spin state of a single electron as well as the hybridization of two-electron spin states. In this paper, we discuss a model that describes the transport cycle in this regime, including the effects of an oscillating magnetic field (causing electron spin resonance) and the effective nuclear fields on the spin states in the two dots. We numerically calculate the current flow due to the induced spin flips via electron spin resonance and we study the detector efficiency for a range of parameters. The experimental data are compared with the model and we find a reasonable agreement. A. IntroductionRecently, coherent spin rotations of a single electron were demonstrated in a double quantum dot device [1]. In this system, spin-flips of an electron in the dot were induced via an oscillating magnetic field (electron spin resonance or ESR) and detected through a spin-dependent transition of the electron to another dot, which already contained one additional electron. This detection scheme is an extension of the proposal for ESR detection in a single quantum dot by Engel and Loss [2]. Briefly, the device can be operated (in a spin blockade regime [3]) such that the electron in the left dot can only move to the right dot if a spin flip in one of the two dots is induced via ESR. From the right dot, the electron exits to the right reservoir and another electron enters the left dot from the left reservoir. A continuous repetition of this transition will result in a net current flow.Compared to the single dot detection scheme [2], using the double-dot as the detector has two major advantages. First, the experiment can be performed at a lower static magnetic field and consequently with lower, technically less demanding, excitation frequencies. Second, the spin detection is rather insensitive to unwanted oscillating electric fields, because the relevant dot levels can be positioned far from the Fermi energies of the leads. These electric fields are unavoidably generated together with the oscillating magnetic field as well.The drawback of the double-dot detector is that spin detection is based on the projection in the two-electron singlet-triplet basis, while the aim is to detect single spin rotations. However, this detection is still possible because the electrons in the two dots experience different effective nuclear fields. This is due to the hyperfine interaction of the electron spins with the (roughly 10 6 ) nuclear spins in the host semiconductor material of each quantum dot [4][5][6][7][8][9][10][11]. In order to provide more insight in this double-dot ESR detection scheme for single spin rotations, it is necessary to analyze the coherent evolution of the two-electron spin states together with the transitions * Electronic address: f.h.l.koppens@tudelft.nl; Kavli Institute of NanoScience Delft, P.O. Box 5046, 2600 GA Delft, The Netherlands in the transport cycle.In this paper, we discuss a mod...

Coherent Control of a Single Electron Spin with Electric Fields

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