Nondestructive Real-Time Measurement of Charge and Spin Dynamics of Photoelectrons in a Double Quantum Dot

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Nondestructive Real-Time Measurement of Charge and Spin Dynamics of Photoelectrons in a Double Quantum Dot

T. Fujita, H. Kiyama, K. Morimoto, S. Teraoka, G. Allison, A. Ludwig, A. D. Wieck, A. Oiwa, and S. Tarucha

Phys. Rev. Lett. 110, 266803 – Published 25 June 2013

Abstract

We demonstrate one and two photoelectron trapping and the subsequent dynamics associated with interdot transfer in double quantum dots over a time scale much shorter than the typical spin lifetime. Identification of photoelectron trapping is achieved via resonant interdot tunneling of the photoelectrons in the excited states. The interdot transfer enables detection of single photoelectrons in a nondestructive manner. When two photoelectrons are trapped at almost the same time we observed that the interdot resonant tunneling is strongly affected by the Coulomb interaction between the electrons. Finally the influence of the two-electron singlet-triplet state hybridization has been detected using the interdot tunneling of a photoelectron.

Received 11 November 2012

DOI:https://doi.org/10.1103/PhysRevLett.110.266803

Authors & Affiliations

T. Fujita^1,*, H. Kiyama¹, K. Morimoto¹, S. Teraoka¹, G. Allison^1,2, A. Ludwig³, A. D. Wieck³, A. Oiwa¹, and S. Tarucha^1,4

¹Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
²Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
³Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, Universitätsstraße 150, Gebäude NB, D-44780 Bochum, Germany
⁴Center for Emergent Matter Science (CEMS), RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan

^*fujita@meso.t.u-tokyo.ac.jp

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Vol. 110, Iss. 26 — 28 June 2013

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Images

Figure 1
(a) A scanning electron micrograph of the typical lateral DQD device. The surface gates for dot formation have $Ti (10 nm) / Au (20 nm)$ metal thickness. A 60 nm thick ${Al}_{2} O_{3}$ insulating layer was formed on top of them by atomic layer deposition. (b) A $Ti (30 nm) / Au (220 nm)$ mask was fabricated on the surface above the DQD with an aperture of 400 nm diameter. (c) Band profile of the HEMT structure. The excitation laser energy is tuned just above the GaAs band gap. The excited electron-hole pair is separated due to the intrinsic electric field.Reuse & Permissions
Figure 2
(a) Stability diagram of the DQD. The dot was initialized to state A(0,4) before light irradiation. (b)–(d) Real-time charge sensing traces of the DQD measured at the resonance points B(0,4)-(0,5), C(1,4)-(0,4), and D(1,4)-(0,5). The 0.5 nA step height in (d) indicates the interdot tunneling event of a single electron charge.Reuse & Permissions
Figure 3
(a) Single photon detection signal observed over a time scale much longer than the interdot tunneling rate. A fluctuation in the current is seen when a single extra charge tunnels between the two dots. At $t = 220 ms$ , the electron escapes from the dot and the current returns to the value indicating the (0,4) state. (b) A schematic picture of the charge number during interdot tunneling of a photogenerated electron. (c) Measured sensor current upon pulse irradiation indicating interdot tunneling of a single photogenerated electron initially trapped in the left dot. (d) Interdot tunneling of a single photogenerated electron initially trapped in the right dot. (e) Histogram of $t_{trapL}$ . Data were taken at the condition of an average thermal electron interdot tunneling time of 10.8 ms. The fitting time constant was $τ_{trapL} = 9.7 ms$ .Reuse & Permissions
Figure 4
(a) Signal indicating two photon detection. After the irradiation, two photoelectrons fill each QD at the same time. The sensor current is stable until one of the two photogenerated electrons escapes from the DQD. (b) Signal when two photogenerated electrons were trapped both in the right dot.Reuse & Permissions
Figure 5
Single photoelectron trapping in (0,1) initialized charge state with (1,1)-(0,2) excited states on resonance measured at (a) 0 T and (b) 50 mT. Photoelectrons are initially trapped in the left dot and resonantly tunnel into the right dot after 2.3 ms and 12.0 ms, respectively. The elongated tunneling time at finite magnetic field indicates the observation of electrons with parallel spin excited into the spin blockade configuration.Reuse & Permissions

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