nanoscale views

A science story first, then a US research ecosystem story later. When we think about using molecules to store energy, it's usually in the context of food or fuel, so that chemical reactions take place - bonds are broken and remade, and in an exothermic reaction, the products end up with more kinetic energy (center of mass motion, molecular vibrations and rotations) than the initial reactants.  Ho…

First, some inside-baseball US funding discussion.  Apologies to my international readers, who likely don't care much about this except in the abstract. Breaking news : According to journalist Dan Garisto , as of April 25, 20206, the president has fired the entire National Science Board .  The NSB helps oversee the National Science Foundation .   From the outside, it had sure looked to me like th…

We've all seen a traditional compass.  A ferromagnetic, magnetized needle is mounted on a rotating bearing (or floated on the surface of a liquid) so that it can rotate in the \(x-y\) plane.  If there is an in-plane magnetic field \(\mathbf{B}\), the needle will rotate to align with that component of the field.  (It stops in the aligned state because of friction; otherwise it would "librate", osc…

No, this is not another grim post about the chaotic US research funding environment.  Instead I wanted to write a bit about a good example of empiricism in experimental condensed matter physics, the use of illumination to (somewhat but not entirely mysteriously) improve electronic transport in 2D electronic systems. This story goes back decades, and it's all about the role of "disorder" and its e…

To the surprise of no one at all, the 2027 presidential budget request is extremely bad for science. Remember, this is largely a political document, and Congress does not have to follow this. In the past year, Congress largely ignored the recommendations and appropriated a much flatter budget (though agency priorities are still set by the PBR for executive agencies). This new request shows that V…

- This article in ars technica is about this paper, in which a quantum interference experiment is performed that, in the most straightforward interpretation, involves superpositions of states where "event A preceded event B" and "event B preceded event A". This is in the same mind-zapping vein as quantum eraser experiments. I haven't read this in detail, but my typical takeaway from these things …

Matthew Schwartz of Harvard has made a big recent splash, between his public Aspen talk "10000 Einsteins" a year ago about the role of AI and the future of physics, and his talk last week at the APS Global Physics summit on the same topic, and now with this essay, "Vibe Physics: The AI Grad Student", on the website of Anthropic (producers of the AI tool Claude). The essay talks about how Prof. Sc…

Since I headed home early this afternoon, I was only able to go to a couple of talks this morning. Here are those highlights, and a couple of general observations about the meeting. - Piers Coleman gave a very interesting talk that put me onto an experimental puzzle I'm sorry to say I had not seen previously. Some context: It is now well-established that one can do spin-polarized scanning tunneli…

It was another eclectic day at the APS Global Physics Summit. Here is a selection of highlights based on my stochastic sampling of talks. - I've written before about CISS (the chirality-induced spin selection effect). Joe Subotnik gave a neat invited talk related to this, based on something I'd never really considered. In physics we learn about the Born-Oppenheimer approximation, which basically …

Today was again a bit random, as I had talks for both one of my students and me, and meetings with folks. Some highlights: - Edoardo Baldini gave a very nice talk about exotic phases and collective excitations in van der Waals magnets. This included using second harmonic generation microscopy and polarimetry to look at the evolution of magnetic phases in NiPS3 as a function of thickness, ending u…

I hit a pretty random assortment of talks on my first day at the APS Global Physics Summit, after catching a very early flight to get to Denver. Here are a few highlights: - My colleague Hanyu Zhu gave a nice talk about the coupling between chiral phonons (vibrational excitations of atomic motion that carry net orbital angular momentum) and their coupling to electronic spins. For example, chiral …

Next week is the annual APS conference that was once the March Meeting and is now the combined March/April "Global Physics Summit". As I've done annually, I will try to give some impressions of interesting talks that I see, hopefully at an understandable level. This year I'm only there from Monday through late Thursday morning, so I may miss exciting things - hopefully people will still discuss s…

Prof. Leggett was a soft-spoken, kind person who was also a brilliant theoretical physicist. I was fortunate enough to first meet him back when I was a graduate student working in Doug Osheroff's lab. Doug had discovered (along with his thesis advisors Bob Richardson and Dave Lee) the superfluid phases of the rare isotope of helium, 3He in 1972. [Science digression: 3He atoms are fermions - if yo…

I've been attending a lot of talks lately about AI/machine learning and multiscale modeling for materials design and control. This is a vast, rapidly evolving research area, so here is a little background and a few disorganized thoughts. For a recent review article about AI and materials discovery, see here. There is a ton of work being done pursuing the grand goal of inverse design - name some d…

- Appropriators in Congress largely went against the FY26 presidential budget request, and various spending bills by and large slightly-less-than level-funded most US science agencies. A physics-oriented take is here. The devil is in the details. The AAAS federal R&D dashboard lets you explore this at a finer level. Nature has an interactive widget that visualizes what has been cut and what remai…

At present (or near-future) levels of technology, as far as I can tell this idea makes no sense. I will talk about physics reasons here, though there are also pragmatic economic reasons why this seems crazy. I've written before that I think some of the AI/data center evangelists are falling victim to magical thinking, because they come from the software world and don't in their heart of hearts ap…

After seeing this latest extremely good video from Veritasium, and looking back through my posts, I realized that while I've referenced it indirectly, I've never explicitly talked about the Aharonov-Bohm effect. The video is excellent, and that wikipedia page is pretty good, but maybe some people will find another angle on this to be helpful. The ultrabrief version: The quantum interference of ch…

A friend pointed out that, while I've written many posts that have to do with , I've never really done a concept post about it. Here's a try, as I attempt to distract myself from so many things happening these days. The superconducting state is a truly remarkable phase of matter that is hosted in many metals (though ironically not readily in the pure elements (Au, Ag, Cu) that are the best ordina…

The Kondo effect is a neat piece of physics, an archetype of a problem involving strong electronic correlations and entanglement, with a long and interesting history and connections to bulk materials, nanostructures, and important open problems. First, some stage setting. In the late 19th century, with the development of statistical physics and the kinetic theory of gases, and the subsequent disc…

This is a compilation of posts related to some basic concepts of the physics of materials and nanoscale physics. I realized the other day that I hadn't updated this since 2019, and therefore a substantial audience may not have seen these. Wikipedia's physics entries have improved greatly over the years, but hopefully these are a complement that's useful to students and maybe some science writers.…