Grant application post-mortems

This week the Australian Research Council announced which grant applications were successful for funding for next year. So roughly 20 per cent of people were happy and 80 per cent were sad. After the exhiliration or devastation inevitably come the post-mortems, particularly from those who are unsuccessful. We offer each other a multitude of possible reasons for failure or success....

Professor Z was on the committee and he doesn't like my Ph.D advisor.... All they care about is number of publications.... They must have liked the bit I wrote about... Clearly they want people who work at the interface of chemistry and physics... I need more Nature papers.... I should have promised less... It is because I did not have a big name person on the grant... it is because I am working on such a hot topic.... Obviously they aren't going to fund 2 groups working in my area.... I think Dr. X must have been that negative referee... You need to promise lots ....People think my group has too much money....

The problem with this is that this is all speculation. There is usually NO evidence for any of these ideas. Most funding decisions involve a black box. Input is your application which contains tens of pages of information. The output is binary information: yes/no. The output has a large random and subjective element to it.

As scientists we should only draw conclusions based on the evidence at hand.
If you did not succeed, don't take it personally and give up. Keep applying.
If you did succeed, don't let it go to your head.

de Broglie on quantum foundations

In the latest APS News there is a This Month in Physics History column on Louis de Broglie. It contains an interesting quote:

[de Broglie] tried to develop a causal model to replace the probabilistic models of quantum mechanics, which was refined by David Bohm in the 1950s and known as the de Broglie-Bohm theory. While most of his colleagues embraced the notion that the statistical nature of atomic physics was all that could be known, de Broglie believed that “the statistical theories hide a completely determined and ascertainable reality behind variables which elude our experimental techniques.”

This was similar to Einstein's view and has been given a very concrete expression in Stephen Adler's work discussed here.

Deconstructing charge transport in organic semiconductors

A key question about charge transport in organic molecular materials is:

What is the relative importance of disorder and dielectric relaxation [small polarons = Marcus-Hush theory] in determining the charge mobility?

There is a nice clear and succinct review article in Chemical Reviews from 2007 by Coropceanu et al.

The view that disorder is dominant has been advocated by Bassler and collaborators, in
terms of a Gaussian density of states. This leads to a  mobility with the temperature dependence

[I have not seen an analytical derivation, this seems to be based on curved fitting to the results of Monte Carlo simulations].
This is in contrast, to an activated form.

Aside: Coropceanu et al. claim "there is no full theoretical justification for such an Arrhenius like expression". I am mystified by this claim. Small polaron theory [and equivalently Marcus-Hush theory, together with the fluctuation-dissipation theorem] give such a form. Indeed, in the review article they later give such expressions.
But, that is not my main point.

It is also pointed out that distinguishing between these two models is difficult
with experimental data from a limited temperature range.
This can be seen clearly in the Figure below taken from a 2003 paper Low-k insulators as the choice of dielectrics in Organic Field-Effect Transistors

Hence, just because one can fit the data to one of the models one should NOT conclude that model is correct. Unfortunately, this is often forgotten...

Presumably measurements down to 1 K may help distinguish the two models, although apparently these devices can malfunction at lower temperature.

I have more to say about this data, and what it may say about the charge transport mechanism,  but will leave that for another day...

A Reconstructed view of the "Fermi surface".

Mike Norman writes some of the nicest and most helpful review articles about the cuprate superconductors. They are balanced and insightful. This week at the cake meeting we are discussing his latest, Fermi surface re-construction and the origin of high-temperature superconductivity. It gives a succinct summary of the issues raised by the observation of quantum oscillations associated with Fermi surface features iin the underdoped cuprates. It is impressive the way Norman is so objective and does not push any of his own significant contributions as being the "answer".

A few things I learnt

The importance of the negative sign of the Hall constant.

One can only produce electron pockets near x=1/8 with a magnetic stripe potential.

It is not clear where the "spin zeroes" associated with quantum oscillations are.

A few minor comments

Perhaps he gives too much credit to the initial claims from 1992 of observation of quantum oscillations, based on explosive experiments at Los Alamos. He mentioned criticisms by Springford et al. that the data was all noise. Should people get any credit for making unjustified claims based on dodgy data, just because the claimed effect turns out to be real. 

The unresolved issue of closed Fermi surface pockets vs. open arcs is perhaps not emphasized enough. Perhaps Norman leans too much towards pockets.

From a biophysics Ph.D to energy consulting

A group of Biophysics students made a very impressive video featuring my former Ph.D student Joel Gilmore discussing his job working on renewable energy policy for Roam Consulting.

Cooking up a new physics course

Last week the New York Times had a fascinating article [in the Dining and Wine section!] about a new physics class at Harvard, Science and Cooking: from Haute Cuisine to Soft Matter Science. The course is for liberal arts majors, and features guest lectures from and problems assigned by (!) famous chefs.

Physics research rocks on prime time!

A great scene in The Big Bang Theory (Season 3, Episode 4) is where Sheldon and Raj stare at a whiteboard trying to figure out how to detect dark matter. It is done to the tune of The Eye of the Tiger.