Definitive Measurement of Spin-Triplet Superconductivity

I must be out of it, because I thought that there had already been a definitive measurement of such spin-triplet superconductivity before this. But based on this latest report, it appears that NMR measurement of such superconductivity has not been "definitive" until now.

To clarify, the Cooper pair states in most superconducting material are formed due to the pairing of electrons forming what is known as the singlet state. This is when the spin of one electron pairs with another electron that has an opposite direction of spin. Via Pauli Exclusion principle (or rules for fermions), these two electrons can be quite close to one another in space because they do not occupy the same spin states.

However, the physics also allows for the two electrons to pair up with their spins in the same direction. Unfortunately, again due to Pauli, because they have the same spin state, their spatial state cannot be the same, i.e. they can't be too close to one another. This is a more difficult way to sustain this pair. The reason why this is called the triplet state, as opposed to the single state of the more common pairing, is because quantum mechanics allows for three possible ways for these electrons to pair up (see figure below) when we make a measurement along a particular direction.

 

I think that this is a very good exercise to be included in an intro QM class because it is showing something very basic that could be used in such a class and it represents an application to a very important and advanced idea in condensed matter.

 

Zz. 

 

Imaging the Milky Way

If you missed it, I posted how I have gotten into astrophotography lately ever since I got a smart telescope earlier this year.

One of the things that I've always wanted to image is our Milky Way galaxy. Unfortunately, living in the suburbs of Chicago and with the light pollution (Bortle 9), it was almost impossible. I've been waiting for an opportunity to go elsewhere and attempt this. Well, that opportunity came last week when I got to spend a couple of week out in Hawaii (Kauai and Oahu, which BTW have been constantly on my mind the past couple of days due to Hurricane Lala). I brought the telescope with me with the intention of trying to see if I can do something. Didn't get clearly skies in Kauai, and didn't have clear skies in Oahu either until 3 days before we left.

On the beaches of Ko Olina in Oahu, we managed to finally capture the image of the center of the Milky Way using our Dwarf Mini telescope:

It turned out better than I expected. It took about half an hour of stacking to get this image. I wish we had more time to be able to do a mosaic because I wanted to try an image above and below the enter, but the clouds were already moving in. Still, we were pleased that we managed to accomplish our main goal.

And yes, you can bet that I'll be showing this in my astronomy class this Fall! 😊

Zz.
 

Are Quasiparticles Real?

I'm posting this because someone here (@dougnatelson) can respond to this. This is based on this article that asks if quasiparticle are real.

In much the same way, "quasiparticles can only exist within some medium or material, because they are built up from the response of that material's constituents or building blocks," Natelson said; in contrast, particles such as electrons and protons "can exist in free space."

In other words, quasiparticles can't exist in a vacuum and they can't exist on their own. They're reliant on particles acting together and being in a material where they can emerge, just as a wave carried out in a stadium can only exist when there is a group of people there who can perform it.

As a condensed matter physicist, I'm quite familiar with the concept of "quasiparticles", since we deal with electrons, "holes", etc. that undergo many-body interactions. It is why, for example, charge carriers in solids have "effective mass", which is typically not the "bare mass" of the charge carrier, but the "normalized" mass due to such many-body interactions. In essence, we have reduced one many-body problem into many one-body problem by lumping the complicated many-body interactions into this new particle's mass. This particle is often called the "quasiparticle".

But the above is a highly simplified picture. Some people would say that this is the Fermi Liquid model of quasiparticles where the strength of the coupling between the particle and the many-body interactions are "weak", allowing for such simplification. This is no longer true for particles with strong interactions where the Fermi Liquid model breaks down (marginal Fermi Liquid and so on). Therefore, it can get very complicated, especially when you add particles in reduced dimensions (2D and 1D).

I like this article because it highlights a very basic concept in condensed matter physics that does not get the appropriate publicity. However, the one issue that is missing is the explanation on what we mean by "real". Is an electron "real" based on what we measured the "bare electron" properties? After all, if we buy into the idea of quantum field theory, even a bare electron has its own vacuum interactions. This leads to the crazy idea that particles actually are all the result of some kind of many-body interactions themselves, i.e. they are quasiparticles!

Instead of worrying whether something is "real", whatever that means, we should be focusing on fact that we can measure such-and-such properties of such-and-such a thing. The measurements, or rather, the outcome of the measurements are real for they can be reproduced. The measurements represent the characteristics and properties of the entity that we are measuring. Maybe this is carrying empiricism to the extreme, but it beats trying to convince people that it is "real".

😊

Zz. 

 

Entanglement and Experiment

The AIP has produced one of the most informative historical account of the history of quantum entanglement after EPR, especially on its development before Bell came up with his infamous inequality test. It is a two-parter, so you definitely want to read both.

Entanglement and experiment, part 1: Before Bell

Entanglement and experiment, part 2: Oral history of the first Bell tests

What I was not aware of was the early experiment by Chien-Shiung Wu in this area. She is definitely one of the giants of physics that should have been awarded the Nobel Prize. I'm glad this article finally gives her the recognition that she deserves, and it certainly gives me even more reason to admire her accomplishments.

Zz. 

ChatGPT Is Still Not Very Good With Sketching

I gave this prompt to ChatGPT:

Sketch an object moving in a circular path, showing the tangential velocity at 4 different points along its path.

This was the image that it gave me:

 

I then gave what I thought a simpler prompt:

sketch an object moving in a circular path having a centripetal force

... and this was what I got:

 

 

I guess it is worth a giggle.

Zz. 

Astrophotgraphy - As If I Need A New Hobby

I got the new Dwarf Mini smart telescope for my birthday this year. I never had a desire for a telescope before even though images of these remote places in our universe had always fascinated me. It also helps that I teach basic Astronomy for students wanting a GED science credits.

However, when I came across videos of the Dwarf Mini and saw how compact and stylish it was, I made a mistake of expressing my fascination to it to the people around me and voila! It showed up as a birthday present!

Ever since a month ago, I have been fiddling around with it and have really gotten into this astrophotography thing. I must say, it has been quite fascinating and educational, because I ended up reading about the stuff that I photographed.

Anyhow, here are a few pictures that I've taken so far. Mind you, we have not been getting a lot of clear skies so far, and on days that we do have them, they have been rather chilly except for a few days. I'm hoping this will change soon now that this is the first day of Spring.

The telescope came with a solar filter which allows me to take a snapshot of the Sun. Here comes the Sun, with a few sun spots!

 

Next comes the closest spiral galaxy to the Milky Way, the Andromeda galaxy (M31), which Edwin Hubble discovered to be at a location much further than the size of the Milky Way and thus, proving that this not not part of our galaxy. I've removed the stars in the photo, but you'll notice that the image kept two additional galaxies.

This next one is the one that was at the top of my list. This is the Orion Nebula (M42), a star nursery in the Orion constellation. This is a popular shot because it is one of the brightest nebula for astrophotography. I was quite impressed by what the Dwarf Mini was able to do.

Finally, this was obtained just last night. We had clear skies, and so I wanted to see if we could capture the Rosette Nebula (NGC 2237). We got it, but I think we needed to go twice as long to get a better and clearer image.

Except for the Sun, each one of these images took about 1 hour and 15 minutes to complete. The telescope basically tracked and stacked a series of images that it took. Each image had about 15-30-second exposure time. I left it up to the telescope auto settings for each of the items store in its library.

My next goal is to capture a few more galaxies, maybe an elliptical one, or even the Magellenic cloud (LMC) and see how that looks.

Zz. 

 

ChatGPT and Gemini Can't Do Real Physics Research

A rather interesting post on AI's ability to actually do real physics research that beginning graduate students are expected to do.

More than 50 physicists from over 30 institutions built the "CritPt" benchmark ..... The benchmark asks models to solve original, unpublished research problems that resemble the work of a capable graduate student starting an independent project.

Google's "Gemini 3 Pro Preview" reached just 9.1 percent accuracy while using 10 percent fewer tokens than OpenAI's "GPT-5.1 (high)," which placed second at 4.9 percent. Even at the top of the leaderboard, the systems miss the vast majority of tasks.

It is fascinating to note that, based on this, the current AI engines do not seem to exhibit a clear ability for creativity and creative thinking that is not based on existing knowledge that they can refer to. They are "good" at stitching and pasting together information from various sources to come up with an answer, but not when there is nothing existing in the first place.

I actually had a chuckle when I read this part:

The models often produce answers that look convincing but contain subtle errors that are difficult to catch, which can easily mislead researchers and require time-consuming expert review.

If you have followed this blog for some time, you would have noticed my posts on my battles with ChatGPT when I gave it basic physics questions that my first-year physics students encounter. See here, here, and here. In many other cases, I find that it gives me the wrong answer but with the correct explanation, or it gives me the correct answer but the explanation simply doesn't match. As the article said, often times the errors are subtle, something that a student learning about the material will probably not catch.

Zz. 

2025 Nobel Prize in Physics

It's unusual that a Nobel Prize in Physics is given to physicists working in the field that was the same as my PhD research work. It finally happened this year.

I did research work in tunneling spectroscopy in cuprate superconductors, and we did both superconductor-insulator-normal metal and superconductor-insulator-superconductor tunnel junctions, the latter of which is where we observe the Josephson tunneling current. Therefore, the work cited here is something that I'm quite familiar with. I just never realized till now that it was such a major discovery to be awarded a Nobel Prize. I know that one of my colleagues had John Clarke as his PhD advisor at Berkeley.

Interesting that this is such an old and well-established phenomenon and technique that is only now being recognized.

Zz. 

A Century of Quantum Mechanics

CERN Courier has a special issue this month celebrating what they consider as the 100th anniversary of Quantum Mechanics.

Of course, the focus here is predominantly on elementary/particle physics. And yet, many of the most obvious demonstration and manifestation of quantum mechanics can be found not in particle physics, but in condensed matter physics. The Schrodinger-Cat type demonstration using SQUIDs, and the clearest manifestation of the effect of coherence can be seen in condensed matter experiment. To quote Carver Mead's article[1]:

Although superconductivity was discovered in 1911, the recognition that superconductors manifest quantum phenomena on a macroscopic scale (4) came too late to play a role in the formulation of quantum mechanics. Through modern experimental methods, however, superconducting structures give us direct access to the quantum nature of matter. The superconducting state is a coherent state formed by the collective interaction of a large fraction of the free electrons in a material. Its properties are dominated by known and controllable interactions within the collective ensemble. The dominant interaction is collective because the properties of each electron depend on the state of the entire ensemble, and it is electromagnetic because it couples to the charges of the electrons. Nowhere in natural phenomena do the basic laws of physics manifest themselves with more crystalline clarity.

Zz 

 [1] C.A. Mead, PNAS v.94, p.6013 (1997); or you may be able to access it here.

Another Sighting of a Possible Fifth Force?

First of all, I'm old! I started being in a student in physics since the early 1980's (do your own math). During all of that time when I have paid attention to physics, I've seen a lot of major milestones, including the discovery of High-Tc superconductors, discovery of exoplanets, the cold-fusion debacle, etc...etc.

The one thing that pops up every now and then is the claim of the possible discovery of this "fifth force". Honestly, even back in the 1980's, there were already such claims being made. None of the have amounted to anything as far as I can tell. Therefore, you can understand my "Oh no, this again?" reaction when I read the latest claim of the possible detection of the Yukawa particle as an indication of the existence of this fifth force (that article contains a link to the actual PRL paper that you can download).

This is not a knock on this work, heavens no. But the publicity surrounding this makes it sound as if this has not happened before. I guess it is not surprising that people have short memory, which is why mistakes are often repeated.

I'm going to wait a year and revisit this post and see if we have gone beyond first based on this discovery.

Zz. 

A Century of Bose-Einstein Condensation

Nature has published a wonderful review of the discovery and progress that we have made in understanding BE condensation since its discovery. It is an open access article and you can download the full article. I definitely like the figure that shows the major milestone in its development, but it would be nice if that is expanded even more to include references, or at least citation numbers so that I don't have to go hunting for them. 

Scanning through the article, I actually did a quick headcount on how many of the names mentioned in the article that I had met personally: Schrieffer, Leggett, Anderson, and Abrikosov. I believe Leggett is the only one still around as of this writing.

I didn't get too much into BE condensation even though I was working in superconductivity at that time. I was transitioning out of that field of study when the big BEC-BCS connection was experimentally established. Still, it was, and still, an exciting field to follow even on the peripheral.

Zz. 

Did I Expect Too Much?

In one of my exam questions, I gave the students the average radius of Earth's orbit around the Sun at 150 million km. I told them that we can assume that the orbit is circular. I even gave them the formula for the circumference of a circle.

The question then asked them to find the speed of the Earth as it moves around the Sun.

After the exam and after the results were published, a number of students told me that I did not give them enough information to solve the problem. They said that they could figure out the circumference of the circle to correspond with the distance that the Earth has traveled, but they don't have any information on the time of travel and thus, can't find the speed.

I argued that they should know this because it is common knowledge.

Did I expect too much? Did I make the wrong assumption that everyone (especially 1st and 2nd year university students) knows that it takes the Earth one year to make one complete orbit around the Sun? Was this something I should have given them?

Zz.