Excitons !

1. Oct 17, 2005

Gokul43201

Staff Emeritus
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.

2. Oct 17, 2005

ZapperZ

Staff Emeritus
Just make sure you don't miss this:

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

Zz.

3. Oct 17, 2005

Gokul43201

Staff Emeritus
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.

Last edited: Oct 17, 2005
4. Oct 17, 2005

ZapperZ

Staff Emeritus
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. Oct 17, 2005

Gokul43201

Staff Emeritus
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.

6. Oct 17, 2005

ZapperZ

Staff Emeritus

Ooooh..... PEDIGREE! PEDIGREE!!

:)

Zz.

7. Oct 17, 2005

Gokul43201

Staff Emeritus
Wait...wait. My advisor was Richardson's (of He-3 fame) grad student at Cornell !

8. Oct 17, 2005

ZapperZ

Staff Emeritus
I HATE YOU!

:)

Zz.

9. Oct 17, 2005

Gokul43201

Staff Emeritus
Now that I'm done showing off my boss' bosses, let's get back to them excitons... <sigh>

10. Oct 25, 2005

Mk

So Zz doesn't have any boss' bosses?

11. Oct 25, 2005

ZapperZ

Staff Emeritus
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. Oct 25, 2005

Mk

I like potato chips.

13. Oct 25, 2005

Gokul43201

Staff Emeritus
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 ?

Last edited: Oct 25, 2005
14. Oct 25, 2005

ZapperZ

Staff Emeritus
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. Oct 25, 2005

Gokul43201

Staff Emeritus
Yes, they're both here. I've sat in some of Randeria's lectures. He's an excellent teacher !

16. Oct 25, 2005

ZapperZ

Staff Emeritus
Nandini, btw, was a student of Phil Anderson at Princeton. So she has quite a pedigree there herself.

Zz.

17. Oct 25, 2005

Gokul43201

Staff Emeritus
I didn't know this - but it sure explains her interest in disordered systems. She was Ashcroft's grad student, at Cornell.

18. Oct 25, 2005

nbo10

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. :rofl:

19. Oct 25, 2005

Dr Transport

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 cancelled 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. Oct 26, 2005

Gokul43201

Staff Emeritus
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. Oct 26, 2005

Dr Transport

Much of their work centered on calculating $$\chi^{(3)}$$ 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.

Last edited: Oct 26, 2005
22. Oct 31, 2005

Gokul43201

Staff Emeritus
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 >

Last edited: Oct 31, 2005