The NSF MRSEC program - end of an era?

Are we witnessing the irreversible deconstruction of an historically successful NSF program, not because of any clear strategy or planning but instead because of the cumulative impact of many forces?

The National Science Foundation has historically supported a mixture of individual investigator (or small team) funding opportunities and large center grants.  The center programs are meant to bring together collaborative teams of researchers to tackle sets of research questions that require a larger scale approach - a hugely emphasized review criterion of those centers is always the question, "Is the proposed work really a center, in the sense of being a coherent effort larger than the sum of its parts, or does it instead read like a collection of loosely connected individual projects?"  Center programs are also a way that NSF has supported Research Experience for Undergraduates programs, providing crucial gateways into real science and engineering research and training for hundreds of students per year.  Similarly, center programs have contributed toward building up networks of facilities with specialized research infrastructure and capabilities.  Apart from topical centers that come and go (e.g., the nano centers in the early 2000s, the quantum centers now), center programs include Engineering Research Centers, Science and Technology Centers, and the less applied Physics Frontier Centers (Division of Physics), Centers for Chemical Innovation (Division of Chemistry), and the flagship center program of the Division of Materials Research, the Materials Research Science and Engineering Centers (MRSECs).

The MRSEC program has such a long history (going back to the 1960s) that it has a reasonably good wikipedia page telling the story of its origins and evolution.  In brief:  There are typically around 20 MRSECs at any one time since the program was shifted into its present form 31 years ago.  Each center award is for six years, renewable.  There is a national competition every three years, during which half of the existing centers are up for renewal (though depending on reports by visiting committees, some centers may be recommended not to submit a renewal proposal).  Research in MRSECs is organized into "Interdisciplinary Research Groups" (IRGs), as well as some seed projects.  Once upon a time, a MRSEC could have as many as five IRGs.  Over the last 15 years or so, NSF budgets have largely been flat, and DMR has tried to balance the demands of individual investigator grants vs. center grants, along with knowing that underfunding a project can be worse than not funding it at all.  As a result, the number of funded IRGs has decreased steadily, so that a typical MRSEC now has two or three IRGs (usually two).  

I won't bore you with details about how the funding competitions work.  The short version:  universities send in preproposals consisting of draft IRGs + the other center components (facilities, education, management, etc.); IRGs are reviewed in panels, and then universities are invited or not to the full proposal stage.  Suffice it to say, every three years there is a national competition that consumes many many hours of effort.  Landing a MRSEC is both a sponsored research award and a point of pride.  Typically maybe 80% of the cohort up for renewal make it, with new starts making up the balance, so that there is some rotation among institutions.   Like all NSF programs, the peer review efforts are done for free by the community.

The MRSEC program has had a big impact over the years, at minimum in the number of people trained and supported through these efforts.  The National Research Council/NAS did a study of the MRSEC program back in 2007 that is publicly available here, if you're interested.  No program is perfect, and I don't want to argue about whether the balance of, e.g., reporting requirements vs. research dollars is right, etc.  However, I think the large majority of materials researchers in the US would say that the MRSEC program is a mainstay that has been a key pipeline of people into the field, both in academia and industry.

This year, I worry that we are watching likely irreversible harm to the program, and not by the voluntary choice of anyone at NSF.   The budgetary uncertainty is crushing right now.  It is unclear when and how the agency will be making awards, and how much funding they will have (since you can't actually plan based on the possibility of a continuing resolution in the absence of actual budget bills that can pass congress).  As a result, after the preproposal phase in the current competition, NSF revised their guidance, so that instead of the typical "8-10 awards" expected (see here), now they say to expect "2-5 awards".  That's because they're doing contingency planning assuming a cut in the program from $27M to $15M.  This means that there is a real possibility that the total number of existing MRSECs could be cut by 40% at a stroke, and the next cycle of the competition will be due to start in 2028, with little reason to think that budgets will be any better or smoother by then. 

There will almost certainly never be a return to "normal", for multiple reasons, including the general evolution of all funding programs with time.  The end result of the current shakeup may also have some positive outcomes in terms of new approaches.  That said, it sure feels like paths are being set by circumstances, not considered choice.  I would say that the path of this program is a question that should be addressed by the NSF Math and Physical Sciences advisory committee, but of course that was disbanded back in April, along with 11 others.  You might imagine asking the National Academies for thoughts on this, but I gather anecdotally that is not happening much at all anymore either.  

I'm writing because I hope someone more influential than me can report on this.  At a time when "materials" are clearly of major importance to US competitiveness (e.g., they are clearly relevant to multiple priority areas of the Genesis Mission), is anyone thinking about the impact of the trajectory we are on here?

(Back to science soon, hopefully.)

Taking stock: some federal science news

Some general science news:

•  The New York Times ran an interactive article this week that shows what we all know.  This past year was a very bizarre funding environment.  The article focuses on NIH and NSF, but the major points are generalizable.  The combination of circumstances (DOGE, general administrative turmoil, uncertainty and legal cases about indirect costs, the lack of a real budget followed by a late continuing resolution, plus the government shutdown and continued lack of real budgets) has been extremely disruptive, resulting unquestionably in less science and engineering research being funded by the US government than in many years.  
• Conversations I've had with program officers at two agencies have conveyed that everyone thinks it is very likely that there will be another shutdown in January, when the present spending authority expires.  To put that another way, there is very little confidence that actual spending bills appropriating real budgets for NSF, DOE, NIH, etc. will pass the House and Senate, with some reconciled conference version getting filibuster-proof support in the latter, before then.  This uncertainty means that right now it's going to be nearly impossible for the NSF, for example, to make much in the way of awards in the meantime, since they have no budget and can't plan on a year-long continuing resolution.  
• There has been an executive order announcing the Genesis Mission, which is going to be a large federal AI+science project.  The goal is to "accelerate the AI and quantum computing revolution and to double the productivity and impact of American science and engineering within a decade", according to undersecretary of energy Dario Gil.  Broadly, the plan is to have AI/ML agents developed (presumably by private contractors or private/public partnerships) and trained on vast datasets (ones already in existence in, e.g., national labs and public repositories).  At the same time, a list of Grand Challenges will be defined (within the next 60 days), with the idea that these AI agents will be used to address these (and demonstrating application of the AI "Platform" toward at least one challenge within 270 days).  Any stated support for science and engineering research is welcome.  I hope that this ends up bearing fruit in terms of real research advances, and that university researchers can contribute effectively. (I worry about a framework for massive taxpayer-funded financial support of for-profit AI companies, privatizing financial/IP benefits from publically funded datasets.  Of course, I worry about a lot of things.  Ask anyone who knows me.).   Ideas about grand challenges would be fun to discuss in the comments.   
• We had a great physics colloquium this week from Steve Fetter at the University of Maryland about the continuing threat of nuclear weapons.  Very sobering.  One fact that I gleaned:  In terms of missile defense, the Next Generation Interceptor is likely to cost $660M per interceptor.   That is something like 50 times the cost of a Russian ICBM.  Something else to bear in mind:  The Houston Food Bank, one of the largest and most effective in the US, has an annual budget of about $64M.  The amount of resources consumed by nuclear arms since 1945 is just staggering.

What is the orbital Hall effect?

In the course of thinking about how best to revise my too-math-infused post about quantum geometry, I realized that writing about the orbital Hall effect lays nice groundwork.  

I've previously written about the spin Hall effect (SHE), in which a charge current \(\mathbf{j}_{\mathrm{c}}\) directed along \(\hat{\mathbf{x}}\) generates a net flow of \(\hat{\mathbf{y}}\)-directed spin angular momentum along the \(\hat{\mathbf{z}}\) direction.  This is a consequence of spin-orbit coupling, and it was first predicted in 1971 with a major revival sparked in 1999.  Electrically generating angular momentum currents has proven very useful, leading to many ideas about magnetic memory devices.  Microscopically, it's not easy to develop an intuition about the SHE, though as a spin-orbit effect, it is expected to be much stronger in heavier metals, since the spin-orbit coupling in atomic orbitals scales like \(Z^{4}\), and electronic bands in solids are built from those orbitals.  

That fact, that the electronic bands originate from atomic orbitals, is something that can get lost in a Bloch wave/nearly-free electron treatment of electronic structure.  In the orbital Hall effect, this idea is paramount.  This was explained clearly in this PRL (arXiv here).  The little \(p\)-orbitals are drawn on top of the \(k_{x}-k_{y}\) plane, to illustrate the idea that the electronic states in \(\mathbf{k}\)-space have different orbital content, depending on \(\mathbf{k}\).   The blue circle represents the "Fermi disk", with \(\mathbf{k}\)-states inside the circle occupied, and \(\mathbf{k}\)-states outside the circle empty.  

Adapted from Fig. 1 here.

When no electric field is applied, the Fermi disk is centered on \(\mathbf{k} = 0\); there is no net current, and there is no net orbital angular momentum once all the filled states are considered.  When an electric field is applied in the \(+x\) direction, though, the Fermi disk is shifted away from the origin in the \(-x\) direction (because of our convention that electrons are negatively charged).  Now adding up the \(z\)-directed orbital angular momentum contained within the Fermi disk, there is net \(+z\) orbital angular momentum carried by states with positive \(k_{y}\), and net \(-z\) orbital angular momentum carried by states with negative \(k_{y}\).  So, for this orbital texture, a charge current \(\mathbf{j}_{\mathrm{c}}\) directed along \(+\hat{\mathbf{x}}\) generates a net flow of \(\hat{\mathbf{z}}\)-directed orbital angular momentum along the \(+\hat{\mathbf{y}}\) direction.  Charge current generates a transverse flow of orbital angular momentum, entirely due to the way atomic orbitals come together to make Bloch states in \(\mathbf{k}\)-space, independent of any spin-orbit physics.  That's why the orbital Hall effect has been inferred experimentally in several materials with weak spin-orbit effects, like chromium and titanium.

These effects can be large, and orbital Hall physics plus some \(\mathbf{L}\cdot\mathbf{S}\) coupling may be responsible for some of the results labeled as spin Hall.  See here for a discussion.  Electrically pumping around angular momentum through orbital and spin Hall effects, and their inverses, is the idea behind a variety of device concepts for memory (e.g. here) and logic.  Fun stuff.

Quantum geometry - some intuition

There has been a great growing interest in quantum geometry in recent years.  Last week, I heard an excellent talk by Raquel Queiroz about this that gave me a more physically intuitive interpretation  of this topic.  The more formal write-up is in this preprint from this past April, which I'd missed at the time.

Caution:  Math incoming.  I will try to give a more physical picture at the end.  I know that this won't be very readable to non-experts.    

As I've written before,  (e.g. here and a bit here), the electronic states in crystalline solids are often written as Bloch waves of the form \(u_{n\mathbf{k}}(\mathbf{r})\exp(i \mathbf{k}\cdot \mathbf{r})\), where \(u_{n\mathbf{k}}(\mathbf{r})\) is periodic in the spatial period of the crystal lattice.  For many years, the \(\mathbf{k}\) dependence of \(u_{n\mathbf{k}}(\mathbf{r})\) was comparatively neglected, but now it is broadly appreciated that this is the root of all kinds of interesting physics, including the anomalous Hall effect and its quantum version.  

We can compute how much \(u_{n\mathbf{k}}(\mathbf{r})\) changes with \(\mathbf{k}\).  The Berry connection is related to the phase angle racked up by moving around in \(\mathbf{k}\), and it's given by \( \mathbf{A}(\mathbf{k}) = i \langle u_{n\mathbf{k}}| \nabla_{\mathbf{k}}| u_{n\mathbf{k}} \rangle \).  One can define \(\mathbf{\Omega} \equiv \nabla \times \mathbf{A}(\mathbf{k})\) as the Berry curvature, and the "anomalous velocity" is given by \(-\dot{\mathbf{k}}\times \mathbf{\Omega}\).  

If we worry about possible changes in the magnitude as well, and \( |\langle u_{n\mathbf{k}}| u_{n\mathbf{k+dk}} \rangle |^{2} = 1 - g^{n}_{\mu \nu}dk_{\mu}dk_{\nu}\) plus higher order terms.  The quantity \(g^{n}_{\mu \nu}\) is the quantum metric, and it can be written in terms of dipole operators:  \(g^{n}_{\mu \nu}= \sum_{m\ne n}\langle u_{n,\mathbf{k}}|\hat{r}_{\mu}|u_{m \mathbf{k}}\rangle \langle u_{m,\mathbf{k}}|\hat{r}_{\nu}|u_{n \mathbf{k}}\rangle\).  The quantum metric quantifies the "distance between" the Bloch states as one moves around in \(\mathbf{k}\).  

That last bit is what I really learned from the talk.  Basically, if you try to consider electrons localized to a particular lattice site in real space, this can require figuring in states in multiple bands, and the matrix elements involve dipole operators.  The quantum geometric tensor \(g_{\mu \nu}\) quantifies the dipole fluctuations in the electronic density.  You can define a lengthscale \(\ell_{g}\equiv \sqrt{\mathrm{Tr} g}\), and this can tell you about the spatial scale of polarization fluctuations relative to, e.g., the lattice spacing.  Metals will have essentially divergent fluctuation lengthscales, while insulators have nicely bound charges (that give peaks in the optical conductivity at finite frequency).   The quantum geometry then influences all kinds of experimentally measurable quantities (see here).  

Neat stuff.  Someday I'd like to return to this with a nice cartoon/animation/presentation for non-experts.  The idea that there is so much richness within even relatively "boring" materials still amazes me.

Vortices everywhere

The 2026 APS Oliver E. Buckley Prize in condensed matter physics was announced this week, and it's a really interesting combination of topics that, to a lay person, may seem to be completely unrelated.  

Fig. 1 from this follow-up PRB.

On the one hand, John Reppy (at age 94!) and Dave Bishop were honored for their work examining the properties of vortices in thin films of superfluid helium-4.  Relevant papers include this one from 1977, where they used a torsion pendulum coated with the helium film to examine the transition between normal and superfluid.  When the helium becomes a superfluid, it has (at low speeds) no viscosity, so it no longer has to rotate with the torsion pendulum; this means the rotational moment of inertia goes from that of (pendulum+helium) to just (pendulum), and the period of the oscillations increases.  Really detailed measurements of the oscillations and their damping allowed Reppy and Bishop to compare with models of the superfluid transition based on work by Kosterlitz and Thouless (and Berezinskii).  See the image for a diagram of the experimental setup - very clever and intricate.  

The key idea here is the role of vortices.  Superfluidity in helium is described by an order parameter that looks like a wavefunction - it has an amplitude, \(\Psi_{0}\), and a phase \(\phi\), so that \(\Psi(\mathbf{r}) = \Psi_{0} \exp(i \phi)\).   That order parameter is supposed to be single-valued, meaning if you go around a closed loop of some kind, that phase will either remain the same or ramp by some integer multiple of \(2\pi\).  The gradient of the phase is related to the velocity of the superfluid, so if the phase winds by \(2\pi\), that implies there is a circulation of flow and orbital angular momentum that has to be an integer multiple of \(\hbar\).  In the BKT theory, the demise of the superfluid phase as the system is warmed happens through the creation and unbinding of vortex-antivortex pairs.

On the other hand, the other recipients of the Buckley Prize were Gwendal Fève and Mike Manfra for their work (experiments here and here) regarding the braiding statistics of anyons in fractional quantum Hall systems.  I'd written about anyons here.  For electrons in 2D, the wavefunctions of excitations of the fractional quantum Hall system look like vortices.  The phase of the electronic wavefunction can wind due to circulation, and because electrons are charged, the phase can also wind due to magnetic flux attached to the little whirlpool.  It's the combination of these phase effects that can lead to those excitations acting like anyons (so that when two are physically swapped or braided around one another, the wavefunction picks up a phase factor that is not just the \(+1\) of bosons or the \(-1\) of fermions).  

As my friend Dan Arovas pointed out, there was a hope back in the early 1980s that perhaps vortices in superfluid helium would also act like anyons and have fractional statistics.  However, this paper by Haldane and Wu disproved that possibility.  

Vortex shedding, from here.

Because of the relationship between quantum phase winding and actual flow of (density) currents, vortices show up in lots of places in hard condensed matter physics.  Classical vortices are also physically nontrivial objects - they're topological and often seem to have very counterintuitive properties and motions.  Heck, Lord Kelvin was so taken by this that he thought (pre-quantum) that maybe everything is really vortices of some kind.  

Perhaps it is fitting that I am posting this on the 85th anniversary of the Tacoma Narrows bridge collapse.  That classic civil engineering failure was caused by vortex shedding by the bridge coupling to its torsional resonance frequency.  Vortices can have big consequences!  

Science journalism - dark times

At this point it's old hat to decry the problems facing traditional news media.  Still, it is abundantly clear in our late stage capitalist society that there has been a collective business decision over the last 20+ years that, like local newspapers and television news, real science journalism is not a money maker.   Just a few examples:  Seventeen years ago, CNN cut its entire science, technology and environment reporting team.  In 2022, Popular Science ceased publication.  In 2023, National Geographic laid off their staff writers.  Last week, the Wall Street Journal laid off their science and health reporters.  

I have it on good authority that there is now only one science reporter left at the WSJ.  One, at a time when science and technology are more critically important to our rapidly changing society than ever, and there is enormous tumult in the US and elsewhere about how science is or is not supported and is or is not factoring into policy decisions.  All of this is happening at a time when public trust in science is falling.  (Check out this from Science Friday.)  

(updated for context) Leaving aside professional science outlets (the news sections of Science, Nature, and society publications like Physics Today, C&EN, Physics World, Chemistry World), there are some good publications out there, like Quanta and Nautilus (both founded by nonprofits). There are outstanding public writers of science, like Philip Ball, Helen Czerski, Katie Mack, Ethan Siegel, and many others (apologies for the incompleteness of this list).  There are some excellent freelance journalists.  The internet also means that there are many opportunities for great engagement.  For example, the videos from 3blue1brown are uniformly outstanding.  However, there are no filters, and the temptation to be click-baity or sensationalistic is problematic.  

I have no solutions to offer, except that I encourage you to support good science journalism and reporting when you see it.  It's important.

Interesting preprints: chirality-induced spin selectivity + quantum gravity

This continues to be a very busy time, but I wanted to point out two preprints that caught my eye this week.  Their subjects are completely disparate, but they stand out as essentially reviews written in a much more conversational tone than the usual literature.

The first is this preprint about chirality-induced spin selectivity, a subject that I've mentioned before on this blog.  There is now an extensive body of evidence (of varying quality) that there is a connection between structural chirality of molecules and their interactions with the spin angular momentum of electrons.  This includes monolayers of chiral molecules leading to net spin polarization of photoemitted electrons (here), a lot of electronic transport experiments involving chiral molecules and magnetic electrodes that seem to show spin-dependent transmission that is absent with achiral molecules, and even a chirality dependence of molecular adsorption kinetics on magnetic surfaces (here).  The preprint is a provocative discussion of the topic and possible mechanisms, and the importance of precision in the description of the various phenomena.

On a completely different topic, this preprint is a fun discussion about quantum gravity (!) and how condensed matter ideas of "the vacuum" can lead to insights about how quantum mechanics and gravity might need to play together.  One fun bit early on is a discussion of something I like to point out to my undergrad stat mech students:  A single hydrogen atom in a very very large box will apparently (if the usual stat mech formalism of partition functions is valid) be spontaneously ionized, even when the box (which presumably functions as a reservoir at temperature \(T\)) and atom are at temperatures faaaaaar below the energy scale for ionization.  This is discussed nicely in this 1966 article in the Journal of Chemical Education.  Anyway, I thought this was an interesting discussion from three condensed matter theorists.