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UID:69d4b40d311c6
DTSTART:20250604T080000Z
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TRANSP:OPAQUE
LOCATION:ICFO Auditorium and Online (Teams)
SUMMARY:ICFO | MAXIMILIAN HEITHOFF
CLASS:PUBLIC
DESCRIPTION:We investigate the physics of quantum-confined excitons in an e
 lectrostatically defined PN junction. Such a PN junction can be generated 
 in an encapsulated monolayer \\MoSe{} along the patterned edge of a top-ga
 te electrode. Applying a voltage gradient between the top and bottom gates
  results in the formation of an in-plane electric-field gradient in the de
 pletion region and strong doping gradients in the P- and N-doped regions o
 f the PN junction. The exciton experiences an attractive force within the 
 electric field gradient and repulsion from exciton-charge carrier interact
 ions. The combined effects are sufficiently strong to quantize the number 
 of available excitonic states within the potential. We show measurements o
 f these quantum-confined excitons in reflection contrast and photoluminesc
 ence spectroscopy. We demonstrate how the confinement potential results in
  fine structure splitting with linearly polarized excitonic states that ar
 e aligned either along or perpendicular to the top gate edge. The states c
 an be gradually tuned between linear and circular polarization using an ou
 t-of-plane magnetic field. Our particular sample geometry\, where the form
 ation of the PN junction electrically isolates the sample from ground\, al
 lows us to investigate the electrostatic model of a photo-biased PN juncti
 on\, with the bias voltage as an additional tuning parameter of the confin
 ement potential. The bias voltage is modified by the measurement itself an
 d varies with the location of the measurement. We demonstrate how the comb
 ined impact of exciton dissociation and Auger-assisted hot-hole tunneling 
 modifies the bias voltage over a timescale up to. The&nbsp\;bias voltage c
 an be further controlled using a second laser\, which enables the tuning o
 f the energy of the quantized states over the range of. Ultimately\, these
  findings allow us to simulate the exact shape of the confinement potentia
 l and to investigate how the in-plane electric field modifies the internal
  exciton structure\, impacting the exciton oscillator strength\, lifetime\
 , and dissociation. The results of this thesis illustrate the possibilitie
 s to pattern tailored exciton potential shapes for photonic and quantum te
 chnologies.\n&nbsp\;\nWednesday June 04\, 10:00 h. ICFO Auditorium \nThesi
 s Directors: Prof. Dr. Frank Koppens and Dr. Antoine Reserbat-Plantey
DTSTAMP:20260407T073645Z
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