Exploring Excitons in Bilayer Semiconductors and High Magnetic Fields

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Discussion Overview

The discussion revolves around excitons in bilayer semiconductors, particularly in the context of high magnetic fields and the fractional quantum Hall regime. Participants explore literature references, personal insights, and the implications of excitons in nanoscience and Bose condensation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant requests references and insights on excitons, bilayer semiconductors, and their behavior in high magnetic fields.
  • Another participant suggests key literature, including works by J.P. Eisenstein.
  • Some participants share their personal connections to notable figures in the field, discussing their academic lineage and experiences.
  • There are mentions of specific researchers, such as Madarasz and Szmulowicz, who have contributed to the understanding of excitons and biexcitons in quantum confined structures.
  • Concerns are raised about the challenges of measuring exciton lifetimes and the conditions necessary for Bose condensation.
  • One participant expresses interest in the Kosterlitz-Thouless transition and seeks a conceptual understanding without delving into complex mathematics.

Areas of Agreement / Disagreement

Participants share various references and insights, but there is no consensus on specific approaches or interpretations regarding excitons and their properties. The discussion remains exploratory with multiple viewpoints presented.

Contextual Notes

Participants note limitations in their understanding and the complexity of the topics discussed, including the challenges of experimental verification and the need for high-quality heterostructure fabrication.

Who May Find This Useful

This discussion may be of interest to researchers and students in the fields of nanoscience, condensed matter physics, and semiconductor physics, particularly those focusing on excitons and quantum confined systems.

Gokul43201
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Anyone have any good references or insights on excitons; excitons in bilayer semiconductors; excitons in high magnetic fields (fractional quantum Hall regime) or Bose condensation of excitons ?

I'm going through the literature but want to make sure there isn't something useful out there that I've missed.
 
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Just make sure you don't miss this:

J.P. Eisenstein, Science, v.305, p.950 (2004)

Zz.
 
That and his Nature article with MacDonald ! That's where I started from. Thanks, Zz !

Any personal insights ?

Edit : Just found a few threads here where you and others have said something about excitons. Will look through them.
 
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Gokul43201 said:
That and his Nature article with MacDonald ! That's where I started from. Thanks, Zz !

Any personal insights ?

Unfortunately, no. I didn't work in this area, although I did know people who did. So what I understand about it was simply based on what I've read and my conservations with these people. So it's all rather superficial, I'm afraid.

Why are you looking at excitons? Planning on going into nanoscience, are we? :)

Zz.
 
ZapperZ said:
Why are you looking at excitons? Planning on going into nanoscience, are we? :)
Zz.
Ha ha ! That would rake in the dollars, wouldn't it ?

No, this is my exam topic. I'm allowed to use any means available (to a person working in the field) to gather info.

PS : My advisor was Eisenstein's postdoc at Penn State. And our lab works on essentially the same kind of bilayer samples that Eisenstein does.
 
Gokul43201 said:
PS : My advisor was Eisenstein's postdoc at Penn State.


Ooooh... PEDIGREE! PEDIGREE!

:)

Zz.
 
ZapperZ said:
Ooooh... PEDIGREE! PEDIGREE!
:)
Zz.
Wait...wait. My advisor was Richardson's (of He-3 fame) grad student at Cornell ! :biggrin:
 
Gokul43201 said:
Wait...wait. My advisor was Richardson's (of He-3 fame) grad student at Cornell ! :biggrin:

I HATE YOU!

:)

Zz.
 
Now that I'm done showing off my boss' bosses, let's get back to them excitons... <sigh>
 
  • #10
So Zz doesn't have any boss' bosses?
 
  • #11
Mk said:
So Zz doesn't have any boss' bosses?

Says who?

My "boss' bosses" were Ed Wolf (who wrote THE definitive book on tunneling in solids) and Bill Spicer (who almost singled-handedly developed angle-resolved photoemisson spectroscopy).

Zz.
 
  • #12
I like potato chips.
 
  • #13
I remember that Spicer died recently. I thought he founded SLAC or something...didn't know he developed ARPES. Speaking of ARPES, Zz, does the name Randeria ring a bell ?
 
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  • #14
Gokul43201 said:
I remember that Spicer died recently. I thought he founded SLAC or something...didn't know he developed ARPES. Speaking of ARPES, Zz, does the name Randeria ring a bell ?

It sure does. Mohit Randeria collaborates a lot with Mike Norman here at Argonne. He used to spend several months at a time here, and then he went back to Mumbai. I believe he is now there where you are, Gokul? Didn't he also being Nandini with him?

Zz.
 
  • #15
Yes, they're both here. I've sat in some of Randeria's lectures. He's an excellent teacher !
 
  • #16
Nandini, btw, was a student of Phil Anderson at Princeton. So she has quite a pedigree there herself.

Zz.
 
  • #17
I didn't know this - but it sure explains her interest in disordered systems. She was Ashcroft's grad student, at Cornell.
 
  • #18
The department here traced the pedigree of the faculty. I'm amazed at how close knit the community is. My former advisor traces back to Born. And then some how it has dwindled down to me. :smile:
 
  • #19
Two guys who did some fine work in excitons/biexcitons in quantum confined structures are Madarasz and Szmulowicz. Some of their work waas extended by a guy named Balandin to magnetic fields applied to quantum confined structures. The original work was funded by the US govt, they were so successful that the contracts were canceled after 2 years because the experimentalist were that far behind in verifying their predictions.

The book chapter that they wrote is in

http://search.barnesandnoble.com/booksearch/isbnInquiry.asp?userid=zA7kBp4CqI&isbn=0471349682&itm=16
 
  • #20
Dr Transport said:
Two guys who did some fine work in excitons/biexcitons in quantum confined structures are Madarasz and Szmulowicz. Some of their work waas extended by a guy named Balandin to magnetic fields applied to quantum confined structures. The original work was funded by the US govt, they were so successful that the contracts were canceled after 2 years because the experimentalist were that far behind in verifying their predictions.
The book chapter that they wrote is in
http://search.barnesandnoble.com/booksearch/isbnInquiry.asp?userid=zA7kBp4CqI&isbn=0471349682&itm=16
Thanks Doc !

I haven't come across much of their work so far...which it appears, deals with coherent, laser-induced excitons and bi-excitons in GaAs/AlGaAs quantum wires.

I can see why it might be hard to measure anything meaningful in such systems. For one thing, I would imagine the exciton lifetimes are in the few nanoseconds at most. Almost the only way to ensure even a hundred nanosecond lifetime is with bilayer (double quantum well) structures, where the electron and hole are spatially separated, and there a large tunneling resistance. Secondly, only recently have we achieved sufficiently high quality heterostructure fabrication which prevents pinning at low temperatures.

Further, only if you have long lifetimes can you hope for hot excitons to cool and possibly Bose condense...and that's where the fun is !
 
  • #21
Much of their work centered on calculating [tex]\chi^{(3)}[/tex] in exciton/biexciton quantum confined systems like layers and wave guides. Madarasz was my advisor and Szmulowicz was on my committee. My topic was in electronic transport in anisotropic semiconductors, nothing as sexy as quantum confined structures which gives you an idea of the breadth of their knowledge and work.
 
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  • #22
This is related : Is there a good way to understand the Kosterlitz-Thouless (Superfluid) Transition in 2D, without going through Renormalization Group? If anyone has a review that gives a physical picture without going through all the highly non-trivial math that makes up RG, I'd be most pleased to hear about it.

<PS : I do not have the time to learn RG right now...nor likely, the time to understand all 26 pages of the original 1972 paper by K & T :frown: >
 
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