Speaker
Description
In electron transport experiments, a detailed understanding of the electronic states within a system is essential for accurate prediction and modelling of transport behaviour. Single-electron pumps traditionally employ two electrostatic gate potentials to confine individual electrons within a quantum dot and subsequently emit them over an exit barrier defined by the second gate. The emitted electrons possess energies exceeding the Fermi energy of the system. During post-emission propagation, these electrons may undergo energy relaxation through phonon emission. The specific phonon modes involved are determined by the energy scale of the relaxation process, with acoustic and optical phonons constituting the dominant mechanisms in single electron pump devices. Building upon prior work by Fletcher et al. [1], Ubbelohde et al [2] and Johnson et al [3], in which relaxation via longitudinal optical phonons was observed, we report evidence of electron de-excitation mediated by alternative phonon modes at lower magnetic fields. Both Longitudinal Optical (LO) phonons as well as possible Transverse Acoustic (TA) are observed in our device. Understanding the scattering modes of the electrons exiting the pump as well as how to suppress said scattering mechanisms is crucial for experiments that require electron coherence. The two modes of phonon emission are observed in a two-finger-gate electron pump incorporating an additional finger gate that functions as a channel barrier, suppressing electron flow in one of the device channels with the signal at both channels being measured using low noise femtoampere current to voltage preamplifiers.
References
[1] Fletcher, J.D. Physical Review Letters 111, no. 2, 216807 (2013)
[2] Ubbelohde, N. Nature Nanotech 10,46–49, 2014.275(2015).
[3] Johnson,N. Physical Review Letters 121, no. 13, 137703 (2018),
| Apply for student award at which level: | MSc |
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