Camus

Amaha

et al. 2010

Phys. Rev. B

Coherent level mixing in dot energy spectra measured by magnetoresonant tunneling spectroscopy of vertical quantum dot molecules Payette, C; Amaha, S; Yu, G; Gupta, J.A.; Austing, D.G.; Nair, S.V.; Partoens, B.; Tarucha, S.Contact us / Contactez nous: nparc.cisti@nrc-cnrc.gc.ca. We study by magnetoresonant tunneling spectroscopy single-particle energy spectra of the constituent weakly coupled dots in vertical quantum dot molecules over a wide energy window. The measured energy spectra are well modeled by calculated spectra for dots with in-plane confinement potentials that are elliptical and parabolic in form. However, in the regions where two, three, or four single-particle energy levels are naively expected to cross, we observe pronounced level anticrossing behavior and strong variations in the resonant currents as a consequence of coherent mixing induced by small deviations in the nearly ideal dot confinement potentials. We present detailed analysis of the energy spectra, and focus on two examples of three-level crossings whereby the coherent mixing leads to concurrent suppression and enhancement of the resonant currents when the anticrossing levels are minimally separated. The suppression of resonant current is of particular interest since it is a signature of dark state formation due to destructive interference. We also describe in detail and compare two measurement strategies to reliably extract the resonant currents required to characterize the level mixing.

Section: Calculated and Measured Energy Spectramentioning

confidence: 60%

Coherent level mixing in dot energy spectra measured by magnetoresonant tunneling spectroscopy of vertical quantum dot molecules

Amaha

et al. 2010

Phys. Rev. B

“…2 as I and II. The particularly interesting three-level crossing behavior will be discussed in detail elsewhere [13].…”

Section: Discussionmentioning

confidence: 97%

“…We then compute the current carried through the coupled states assuming the level mixing within the probed dot is coherent. Full details of our model will be published elsewhere [13].…”

Section: Discussionmentioning

confidence: 99%

Two-level anti-crossings high up in the single-particle energy spectrum of a quantum dot

Physica E: Low-dimensional Systems and Nanostructures

Austing

et al. 2008

We study the evolution with magnetic field of the single-particle energy levels high up in the energy spectrum of one dot as probed by the ground state of the adjacent dot in a weakly coupled vertical quantum dot molecule. We find that the observed spectrum is generally well accounted for by the calculated spectrum for a two-dimensional elliptical parabolic confining potential, except in several regions where two or more single-particle levels approach each other. We focus on two two-level crossing regions which show unexpected anti-crossing behavior and contrasting current dependences. Within a simple coherent level mixing picture, we can model the current carried through the coupled states of the probed dot provided the intrinsic variation with magnetic field of the current through the states (as if they were uncoupled) is accounted for by an appropriate interpolation scheme.

“…The RT peak current cannot always be understood solely by a simple two-level superposition picture. Novel resonance effects associated with the mixed states in the probed quantum dot, brought about by deviations from an ideal lateral QD confining potential, likely need to be taken in to account [16].…”

Section: Discussionmentioning

confidence: 99%

“…Dark-bright conversion of the RT current is one of the notable features seen at several level crossings. Further study is needed to explore the mechanisms leading to the rich variety of two-level anti-crossing behaviour of the RT current [16].…”

Section: Figures 4(a) and (B) [(C) And (D)]mentioning

confidence: 99%

Two level mixing effects probed by resonant tunnelling through vertically coupled quantum dots

Amaha

Phys. Status Solidi (c)

Gupta

et al. 2008

We study the magnetic (B ‐) field evolution of single‐particle levels in one dot by observing resonant tunnelling (RT) between two weakly coupled vertical quantum dots in series. The B ‐field dependence of the RT current peaks in the spectrum follows closely that of the states of a circular two dimensional harmonic potential. Several prominent two‐level anti‐crossing features are revealed. The RT current changes dramatically on passing through the anti‐crossing point. This can be assigned to the nature of inter‐dot RT though intra‐dot level‐mixed states. (a) Schematic diagram of our device. (b) Measured anti‐cross in the resonant current induced by intra‐dot two level mixing. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)