Pardis Sahafi - London, Royal Holloway College
Semiconductor electron pump devices have shown promise for current standards due to their high accuracy current transport [1]. Further to this, at higher fields and frequencies these pumps demonstrate excitation states corresponding to energies in the microwave range [2]. This suggests possible applications in microwave and THz photonics, an emerging field with applications spanning from quantum information processing to medical imaging. More importantly, it also suggests that by studying the electron pumps detection and emission capabilities, a clearer picture of the inner mechanism of the dynamic quantum dot may be reached.
The electron pump device was studied as a possible detector for single terahertz photons. This would rely on the process where the electron absorbs an incoming photon and leaves the dot. This change in occupancy would be recorded as photon detection. In order to carry out this investigation, an understanding of the dwell time of electrons in the dot is vital. The device is based on a GaAs/AlGaAs heterostructure, with a dynamic quantum dot formed by surface gates and a quantum point contact (QPC) that probes the dots occupancy [3]. Measurements are performed at below 1 K and various magnetic fields. One electron is loaded into the dot by lowering the entrance barrier. Once loaded, both the entrance and exit barrier are set to a similar height, trapping the electron. The dots occupancy is then monitored using the QPC to determine the decay time of the electron. Varying dwell times ranging from few ms to > 10 s are detected depending on barrier heights and magnetic fields in agreement with theory in Ref [4].
[1] - M.D. Blumenthal et al., Nature Physics 3, 343 (2007).
[2] - M. Kataoka et al., Phys. Rev. Lett. 106, 126801 (2011).
[3] - S.P. Giblin et al., APL 108, 023502 (2016).
[4] - J.D. Fletcher et al., Phys. Rev. B. 86, 155311 (2012).
P. Sahafi1,2, S. P. Giblin1, J. D. Fletcher1, C. Emary3, P. See1, J. P. Griffiths4, G. A. C. Jones4, I. Farrer4, D. A. Ritchie4, V. Antonov2, and M. Kataoka1. 1National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW, UK 2Royal Holloway, University of London, Egham Hill, Egham, TW20 0EX, UK 3University of Hull Cottingham Road, Hull, Yorkshire, HU6 7RX, UK 4Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, UK