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SUMMARY:Time-resolved detection of single-electron wave packets - Dr Masay
 a Kataoka - National Physical Laboratory
DTSTART:20160422T090000Z
DTEND:20160422T100000Z
UID:TALK65309@talks.cam.ac.uk
CONTACT:Alessandro Rossi
DESCRIPTION:The recent development of on-demand semiconductor single-elect
 ron sources such as mesoscopic capacitors [1] and leviton excitations [2] 
 has enabled an electronic analogy of quantum optics experiments. This allo
 ws the detailed studies of electron emission dynamics [1]\, fermion quantu
 m statistics [2\,3]\, and the roles of electron-electron interactions [4\,
 5] in electron transport using shot-noise [2\,3\,5] or ac-current [1\,4] m
 easurements. However\, some of the electron dynamics occur at such short t
 imescales that they are inaccessible by the bandwidth of conventional meas
 urement techniques.\n	We demonstrate an experimental method to detect elec
 tron arrival-time distribution with resolutions as small as 1 ps\, and sho
 w that this technique can be used to study the details of electron dynamic
 s in quantum-Hall edge-state transport. Our electrons are emitted from a G
 aAs quantum-dot pump as hot electrons at energies ~100 meV above the Fermi
  energy [6]. These electrons travel through quantum-Hall edge states actin
 g as electron waveguides. A fast-rising detector potential barrier\, drive
 n by an rf signal synchronised to the pump\, acts as a shutter for incomin
 g electrons. The measurements of transmitted electron current provides the
  information on the arrival-time distribution as the time delay of detecto
 r barrier rise is shifted against the timing of electron emission [6\,7]. 
 We have detected electron arrival-time distribution as small as 4 ps.\n	We
  use this technique to perform time-of-flight measurements to deduce edge-
 state velocity [8]. Our results agree with the E ⃗×B ⃗ drift model\, 
 where the electron drift velocity is inversely proportional to the applied
  magnetic field. By measuring the energy dependence of velocity\, we estim
 ate the edge-confinement potential profile\, created by the combination of
  a chemically-etched mesa and a voltage applied to the surface gate that c
 overs the edge. The same time-of-flight technique is used to deduce inelas
 tic scattering rates due to LO phonon emission. We compare these experimen
 tal results against a theory based on Fermi’s-golden-rule calculation [9
 ].\n\n[1] G. Fève et al.\, Science 316\, 1169 (2007). \n[2] J. Dubois et 
 al.\, Nature 502\, 659 (2013). \n[3] E. Bocquillon et al.\, Science 339\, 
 1054 (2013).\n[4] E. Bocquillon et al.\, Nat. Commun. 4\, 1839 (2013).\n[5
 ] V. Freulon et al.\, Nat. Commun. 6\, 6854 (2015).\n[6] J. D. Fletcher et
  al.\, Phys. Rev. Lett. 111\, 216807 (2013).\n[7] J. Waldie et al.\, Phys.
  Rev. B 92\, 125305 (2015).\n[8] M. Kataoka et al.\, arXiv:1512.02906v1.\n
 [9] C. Emary et al.\, Phys. Rev. B 93\, 035436 (2016).\n
LOCATION:MRC seminar room - Cavendish Laboratory
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