Category Archives: The Wire

Interactions, Collective Excitations and a Few Examples

Most researchers in our field (and many outside our field that study, e.g. ant colonies, traffic, fish schools, etc.) are acutely aware of the relationship between the microscopic interactions between constituent particles and the incipient collective modes. These can be as mundane as phonons in a solid that arise because of interactions between atoms in the lattice or magnons in an anti-ferromagnet that arise due to spin-spin interactions.

From a theoretical point of view, collective modes can be derived by examining the interparticle interactions. An example is the random phase approximation for an electron gas, which yields the plasmon dispersion (here are some of my own notes on this for those who are interested). In experiment, one usually takes the opposite view where inter-particle interations can be inferred from the collective modes. For instance, the force constants in a solid can often be deduced by studying the phonon spectrum, and the exchange interaction can be backed out by examining the magnon dispersions.

In more exotic states of matter, these collective excitations can get a little bizarre. In a two-band superconductor, for instance, it was shown by Leggett that the two superfluids can oscillate out-of-phase resulting in a novel collective mode, first observed in MgB2 (pdf!) by Blumberg and co-workers. Furthermore, in 2H-NbSe2, there have been claims of an observed Higgs-like excitation which is made visible to Raman spectroscopy through its interaction with the charge density wave amplitude mode (see here and here for instance).

As I mentioned in the post about neutron scattering in the cuprates, a spin resonance mode is often observed below the superconducting transition temperature in unconventional superconductors. This mode has been observed in the cuprate, iron-based and heavy fermion superconducting families (see e.g. here for CeCoIn5), and is not (at least to me!) well-understood. In another rather stunning example, no less than four sub-gap collective modes, which are likely of electronic origin, show up below ~40K in SmB6 (see image below), which is in a class of materials known as Kondo insulators.

smb6

Lastly, in a material class that we are actually thought to understand quite well, Peierls-type quasi-1D charge density wave materials, there is a collective mode that shows up in the far-infrared region that (to my knowledge) has so far eluded theoretical understanding. In this paper on blue bronze, they assume that the mode, which shows up at ~8 cm^{-1} in the energy loss function, is a pinned phase mode, but this assignment is likely incorrect in light of the fact that later microwave measurements demonstrated that the phase mode actually exists at a much lower energy scale (see Fig. 9). This example serves to show that even in material classes we think we understand quite well, there are often lurking unanswered questions.

In materials that we don’t understand very well such as the Kondo insulators and the unconventional superconductors mentioned above, it is therefore imperative to map out the collective modes, as they can yield critical insights into the interactions between constituent particles or couplings between different order parameters. To truly understand what is going on these materials, every peak needs to be identified (especially the ones that show up below Tc!), quantified and understood satisfactorily.

As Lestor Freamon says in The Wire:

All the pieces matter.

Misconduct and The Wire

Season five of the critically acclaimed TV show The Wire tackles the issue of journalistic fraud and misconduct. In particular, Scott Templeton, a young ambitious journalist at the Baltimore Sun, writes a series of articles where he embellishes details, conjures up quotes out of thin air and ultimately fabricates events. His articles win him wide praise among those in the journalism community. He also garners the Pulitzer Prize, one of the highest accolades one can earn in the field. Even though flags are raised by some of his peers at the Baltimore Sun, at the upper management level, Scott Templeton’s stories are celebrated with enthusiasm.

Of course The Wire is fictional, but at the time The Wire was written, there was precedent for such journalistic falsification. Stephen Glass at the New Republic, Janet Cooke at the Washington Post and Jayson Blair at the New York Times had all been found guilty of journalistic misconduct associated with either plagiarism or fabrication in effort to advance their careers. Cooke was even awarded a Pulitzer Prize for her stories, which she eventually returned.

The reason I bring this all up is because I saw a very strong parallel between the fictional events that occurred in The Wire surrounding Scott Templeton and the actual events that occurred with respect to Jan-Hendrik Schon. In both cases, their notebooks were empty, there were claims by both that their information (e.g. data and notes) had somehow been corrupted and their sources were a closely guarded secret. While working at Bell Labs, Schon famously claimed to use the evaporator in Konstanz, Germany, so that he could “work” in isolation, making it more difficult to for others to reproduce his methods.

The question as to why this kind of misconduct takes place is an interesting one. In the case of Jayson Blair, Wikipedia says:

On the NPR radio show Talk of the Nation, Blair explained that his fabrications started with what he thought was a relatively innocent infraction: using a quote from a press conference which he had missed. He described a gradual process whereby his ethical violations became worse and contended that his main motivation was a fear of not living up to the expectations that he and others had for his career.

As can be gleaned from the quote above, there is little doubt that there is a certain amount of careerism and elevated expectation that is tied in with these instances of misconduct. That these and similar cases occur with relative frequency and happen in different fields suggests that the root cause is societal — an emphasis on perceived career success rather than valuing honesty and hard work. Because this is a sociological problem, all of us have a role to play in correcting it. The solution to the problem may require us to emphasize different values: integrity, meaningfulness of labor and honest motivations. Often these are not the qualities that advance one’s career, but this is because of a lack of emphasis on these values. Perhaps they should.

While the Wire is a fictional show and some readers are no doubt a little fed up with my frequent references to it, I do think that one can learn a lot from its main themes. As Tim O’Brien, author of The Things They Carried, said:

That’s what fiction is for. It’s for getting at the truth when the truth isn’t sufficient for the truth.