Thursday, September 17, 2015

An exciting discovery

A discovery is not always a eureka moment where the a puzzle resolves itself in a burst of insight.  As I realized tonight, we had made a significant discovery of the gradual kind.

A graduate student Sean Mossman, collaborator Rick Lytel and I had been working on a problem for over a year.  We got what we believed was a significant result, so we submitted our work to the best optics journal called Optics Letters.  The reviews came back positive so we started to diligently work on the required revisions.  It was only then that it hit me that this might be a more significant discovery than we had originality imagined.

We have the disadvantage of working in an esoteric branch of a very applied field, so there aren't many people out there that understand or appreciate the work.  Last year I organized a small conference on WSU's campus to bring together people that have worked in this area and have an appreciation for its nuances.  This year, the second meeting in what is becoming an annual event, was held at Lehigh University and organized by a talented experimental physicist, Ivan Biaggio, who was an early appreciator of the power of the sum rules and the guidance they provide in understanding how to make better materials.  The next meeting will take place at Tufts University, and will be hosted by a young and energetic theorist named Tim Atherton.

It is our job to get the word out about our work so that others can reap its benefits and this paper is the first step in the process.

I am too excited to sleep, so to unwind, I am wiring this post.  Below is an email that I sent to my coauthors (typos and all!) of our paper.  I hope it gives my readers some appreciation of the joys associated with doing physics.  Such reward come rarely in the midst of persistent failures.


Dear All,

First, let me say NICE JOB!  Usually after I read through a manuscript a zillion times, I start feeling more and more insecure about the significance of the work with each reading due to becoming desensitized; the sublime becomes the mundane.  However, this is not so with this work.  I truly think it is fantastic.

I have spent a considerable effort on revising the manuscript to address the reviewers' comments and to bring out the wonderful physics that I think was buried in there.  Though I was aware of it  all, as I now you were too, the significance of phase disruption did not strike me until I rewrote the last 4 paragraphs of the paper.

Let me summarize my thoughts.  First, we have shown that phase disruption is associated with a significantly enhanced nonlinear response.  If we go back to our fundamental understanding of a quantum wave function, a kink is only possible where there is an infinite change in the potential; the two classic examples are infinite walls, from which one makes perfect reflectors and ideal boxes to confine particles, and the delta function, which represents the ultimately-bound system.  All such systems are impractical.  That is most likely why researchers have had such difficulty in improving the nonlinear response.

In essence, we have played a great trick on nature by adding a branch that can divert a small electron flux.  As far as the main direction of flow is concerned, the effect on the wave function is the same as one would expect for a delta function.  But, this is easy to do in a nano wire by fabricating a little wart on its surface, or by asking a chemist to add a side group to the bridge that carries electrons between two parts of a molecule.

This may all seem an academic exercise because the original idea was implemented with one electron and there is another requirement that phase disruption must dominate the states near the ground state.  In the case of many electrons, this requires that the phase disruption be concentrated in the states near the Fermi level, which corresponds to the single partial states just below and above the Fermi level.  The problem is that an arbitrary quantum graph will not have this property.  However. all we need to do is to move the little side branch to the right place, and voila, we have a huge nonlinear-optical response.  All this time chemists have been synthesizing all sorts of structures made of all sorts of atoms, and it appears that all that we need to do is move one simple part.

Finally, we propose a very simple molecule that has the right properties to have a huge nonlinear response.  This makes it possible for our ideas to be tested.  I do not expect that the molecule we propose will end up being so great because we have not taken electron interactions into account.  It would indeed be a miracle if this one turned out to work given how everything needs to fine tune in just the right way.  But, with slight modifications of the prong position or length, a project for a seasoned synthetic chemist, and heavy duty calculations by quantum chemists, I think that the right geometry and topology can be identified and experimentally tested.

I will most likely have difficulty sleeping tonight, but I will try to hit the sack soon.  As for the paper, I am passing it along to you for your revisions.  Please keep in mind the ideas above, which I think should be stressed.  So if you make changes, please make sure that they preserve or enhance this narrative.

The response to the reviewers may need more work since I did not get a chance to proof it very carefully.  We need to make sure that we carefully answered all the reviewers comments in the way they intended.  Also, please make sure that our responses match up with the actual changes we made in the manuscript and that we didn't miss anything.

I am willing to read through it all before we resubmit unless you both are comfortable with the final product.  Given that grading is piling up, meetings continue to chew up my time, and I still need to do quite a bit of work for my presentation in DC, any relief from proofing burdens is greatly appreciated!

All the best!

Mark G. Kuzyk
Regents Professor of Physics
Meyer Distinguished Professor of Sciences
Washington State University
Pullman, WA 99164-2814

Phone: 509-335-4672
Fax: 509-335-7816

Web Page:

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