How to control the electron occupation numbers separately in multi-quantum dots?

[PRB147]

How to control the electron occupation numbers separately in coupled quantum dots?
please give some references or some explanation
Thanks.

 

[Cthugha]

What kind of coupling do you have in mind? Are you interested in the kind of coherent coupling needed for quantum gates or do you want to know about radiative coupling like superradiance from QD ensembles?

Also I don't think it is sensible to discuss electron occupation numbers. It should be more convenient to describe the system strictly in terms of excitons unless you are talking about doped QDs, where you usually only knowe the average electron number per dot.

 

[PRB147]

Thank Cthugha for your reply.
I mean the double quantum system, one electromagnetically coupled with the other dot.
one of the quantum dot is n-type, the other is intrinsic and irradiated by laser light, creating the exciton. My question is how to control the electron occupation number in the
n-type quantum dot?

 

[Cthugha]

I am still not quite sure I understand the situation you describe right. I suppose, you have a rather large separation (60 nm or something like that) between the QDs in mind because otherwise I am not sure it is even possible to have a n-type and a neutral QD close to each other (on the order of less than 10 nm) without any external fields. I might however ask my boss, if I stumble across his path. He published some papers on QD molecules.

So let me try to understand you right: Are you interested in the "as-grown" electron occupation, which is always present due to doping or are you interested in the momentary occupation like in experiments concerning electron tunneling between two coupled QDs?

 

[PRB147]

I am interested in the later case,
the momentary occupation like in experiments concerning electron tunneling between two coupled QDs.
Let me restate my problem
We have two electromagnetically coupled quantum dots, the intrinsic one is attached to the two leads, while the other n-type one is not attached to any leads. the two quantum dots are coupled together with the Coulombic interaction, but withot hopping.
My question is how to control the electron occupation number in the n-type QD, as you know, there is no leads to this n-type dot.

Could we control the electron occupation number in the n-type QD through doping?

 

[Cthugha]

Well, you can control the electron occupation number of the n-type dot by doping, but you will most likely not be able to change it once your sample is grown unless you are using some Schottky diode like setup, which would again be using some kind of leads. So it is just the general, not the momentary occupation. I do not know for sure about QD molecules, but my former office neighbour used layers of singly charged QDs for some experiments. I will have a look, whether I find some detailed information about how it was controlled that the QDs were indeed singly charged.

Edit: I do not know, whether this is what you are looking for, but I found some short description of the kind of doping used for growth of the singly charged QDs in one of his paper. See the (freely accessible) supporting online material of A. Greilich et al., "Mode Locking of Electron Spin Coherences in Singly Charged Quantum Dots", Science Vol. 313. no. 5785, pp. 341 - 345 (2006)

Otherwise I could just direct you to some groups working in the field of coupled QDs. As far as I know, the most prominent work in terms of QD molecules has been done by the naval research labs in washington. For example M. Scheibner and D. Kim should have some papers on this. However they are more into quantum gates. Pioneering work concerning the growth of such structures has been done in the group of A. Forchel in Würzburg a few years ago. Here the papers by M. Bayer from his Würzburg times and maybe also some from his own group later in Dortmund might be interesting. From the theoretical side I am not so sure, but papers from T.L. Reinecke and P. Hawrylak might be a good start.

 

[PRB147]

Thank you very much for your valuable reply, please continue, if you get further information