Moore's [Profit] Law

Topological insulators are a fascinating new class of materials that feature an insulating bulk, but metallic surfaces. This means that, although it is the same material through and through (not necessarily a multi-layered heterostructure), electrons cannot travel through the interior of the material, but can easily zoom around at the material’s surfaces. Previously, physicists have only uncovered materials that are purely insulating, semiconducting, or conducting. The discovery of a class of materials that features both insulating and metallic behavior in a single system rocked the condensed matter physics community (the folks who study electrons on periodic crystal lattices), and publications with the words “topological insulator” have increased in number almost exponentially since the early 2000s, when they first started gaining attention.

Publications with "topological insulator" as a topic

The public doesn’t seem to share the condensed matter community’s enthusiasm for topological insulators (TIs), except that they could be used in the next wave of computer chips, as outlined in the New York Times this past January. To the non-physicist, TIs are interesting for their potential applications. To me, TIs are interesting because of their fascinating properties. These are two sides of the same coin, really, since these unique properties are what allow researchers to claim that TIs are the future of the microprocessor industry. However, the public rarely gets a taste of these fascinating properties. If a reporter mentions its conductivity properties, he or she (usually he) says it in passing, and without the kind of wonder and excitement that a physicist might express.

As an example, a recent news piece was published on The Daily Fusion about the potential uses of topological insulators. The Daily Fusion’s goal (according to their website) “is to create a comprehensive news source, covering all aspects of the energy development. Energy issues today are getting increasingly complex and interconnected and have a substantial impact on domestic and world economy, society and environment.” The Daily Fusion neatly summarizes the result of a recent study by a group at UCLA (Fan et al.) by saying that the group has developed a topological insulator that could lead to “low-power, green electronics,” and could “potentially be used in smartphones, computers and other electronic devices.” While this is true (mostly because of the auxiliary verb could), the author seems to miss the crucial point that Fan et al.’s results were obtained at 1.9 K (-456.25 degrees Fahrenheit), which is hardly an ideal operating condition for a device.

The article almost seems to imply that these devices will soon be widely available in consumer electronics, without mentioning the many obstacles that the UCLA group and/or the physics and engineering communities have yet to overcome. Further, articles very rarely mention the possible disadvantages or potential issues with using topological insulators over traditional semiconductors in device applications (authors of graphene articles are often guilty of heralding it the material of the future – but here’s a healthy dose of skepticism). Firstly, the low-temperature behavior will most definitely be different from the high temperature behavior (normal, ambient operating conditions, around 300 K). We have not yet found a TI material with ideal operating conditions at room temperature (or at any temperature, really). Additionally, Fan et al. doped (note: doping is adding controlled concentrations of another element in order to increase device performance) their samples with chromium, since chromium is magnetic. However, chromium is also toxic. These questions need to be addressed in order to determine whether these materials will be implemented, not only for more efficiency, but more sustainably. A proof of concept that the device could work under laboratory conditions is laudable, but not enough.

Engineers are (according to the news, and often the grant proposals, too) primarily interested in the possibilities of TIs because of concerns that the era of Moore’s Law could be drawing to an end, and people are on the lookout for the successor to silicon. In the above NYTimes piece, Stanford professor Shoucheng Zhang was quoted as saying, “Materials are very important to our human societies. Entire eras are named after materials – the stone age, the iron age and now we have the silicon age. In the past they have been discovered serendipitously. Once we have the power to predict materials, I think it’s transformative.” The author of the NYTimes article then goes on to say, “Pushing this research forward is economics – specifically, the staggering cost semiconductor manufacturers are expecting to pay for their next-generation factories…It is quite possible that the computational materials revolution may offer a path toward cheaper technologies for the next generation of computer chips.” I cringe a bit to think that this (my) research is pushed forward by economics and the monolithic corporations that worry about their future profits, and not the basic questions surrounding novel materials that exhibit interesting phenomena. Is it really just for the mortgage? While Science may have been able to appear disentangled from politics and the social world in the past, my field doesn’t even try to pretend anymore. It’s a fuzzy realm, not an objective one, and now everyone knows it, including the funders. 'What is interesting' is increasingly becoming synonymous with 'what is useful', and as Sheila Jasanoff points out, scientists who are dependent upon government funding are now "overselling the promises of research" (Jasanoff 2005). Just keep your skeptical hats on when you read these types of "hot new technology" articles and be prepared to ask questions.