Exploring Excitons in Bilayer Semiconductors and High Magnetic Fields

In summary: Unfortunately, most of the excitons that are created in these systems quickly decay.In summary, Zz thinks excitons are interesting because they play a role in high magnetic fields (fractional quantum Hall regime) and in bilayer semiconductors. He also thinks that excitons in high magnetic fields might be the key to unlocking the mysteries of exciton-photon interactions.
  • #1
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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  • #2
Just make sure you don't miss this:

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

Zz.
 
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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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  • #4
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.
 
  • #5
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.
 
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Gokul43201 said:
PS : My advisor was Eisenstein's postdoc at Penn State.


Ooooh... PEDIGREE! PEDIGREE!

:)

Zz.
 
  • #7
ZapperZ said:
Ooooh... PEDIGREE! PEDIGREE!
:)
Zz.
Wait...wait. My advisor was Richardson's (of He-3 fame) grad student at Cornell ! :biggrin:
 
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Gokul43201 said:
Wait...wait. My advisor was Richardson's (of He-3 fame) grad student at Cornell ! :biggrin:

I HATE YOU!

:)

Zz.
 
  • #9
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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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.
 
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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:
 
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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 sucessful 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 sucessful 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 !
 
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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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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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FAQ: Exploring Excitons in Bilayer Semiconductors and High Magnetic Fields

1. What are excitons and why are they important in bilayer semiconductors?

Excitons are a type of quasiparticle that consist of an electron and a positively charged hole bound together by their mutual electrostatic attraction. In bilayer semiconductors, excitons play a crucial role in the optical and electronic properties of the material, as they can strongly interact with each other and the surrounding environment.

2. How do magnetic fields affect excitons in bilayer semiconductors?

Magnetic fields can significantly impact the behavior of excitons in bilayer semiconductors. They can enhance or suppress excitonic effects, such as exciton binding energy and exciton-exciton interactions. Additionally, magnetic fields can induce new quantum states in bilayer semiconductors, leading to novel optical and electronic properties.

3. What techniques are used to explore excitons in bilayer semiconductors and high magnetic fields?

The most common techniques used to study excitons in bilayer semiconductors and high magnetic fields include optical spectroscopy, magneto-optical spectroscopy, and transport measurements. These methods allow for the characterization of excitonic properties and their response to external stimuli.

4. How can the study of excitons in bilayer semiconductors and high magnetic fields benefit technology?

The exploration of excitons in bilayer semiconductors and high magnetic fields has the potential to lead to the development of new technologies. These could include novel optoelectronic devices, such as excitonic transistors and spintronic devices, as well as advancements in quantum computing and information processing.

5. What are the current challenges in studying excitons in bilayer semiconductors and high magnetic fields?

One of the main challenges in this field is the difficulty in controlling and manipulating excitons in these materials. Additionally, the complex interplay between excitons, magnetic fields, and other external factors makes it challenging to fully understand their behavior. Furthermore, the high sensitivity of excitons to their environment requires precise experimental techniques and careful data analysis.

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