Physics and Physicists

Definitive Measurement of Spin-Triplet Superconductivity

2026-08-20T10:47:29.105-05:00

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

2026-08-16T06:51:48.978-05:00

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?

2026-07-26T10:47:39.221-05:00

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

2026-03-25T09:47:00.005-05:00

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

2026-03-20T12:40:58.719-05:00

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

2026-03-20T08:40:38.927-05:00

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

2025-11-25T11:09:00.000-06:00

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

2025-10-08T14:21:00.002-05:00

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

2025-07-09T13:18:00.007-05:00

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.

[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?

2025-07-08T10:30:00.003-05:00

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

2025-07-01T10:59:00.005-05:00

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?

2025-02-23T09:50:00.004-06:00

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.

100 Years of Quantum Mechanics

2025-02-05T09:15:00.007-06:00

I mentioned earlier of an article on the Davisson-Germer's experiment as part of the commemoration of 100 anniversary of Quantum Mechanics (QM). This is an article describing a bit more of the celebration and the importance of QM. Hint: without QM, none of your modern electronics (computers, smartphones, etc.) will work.

Zz.

The Davisson-Germer Experiment

2025-02-04T09:30:00.005-06:00

As we continue to celebrate 100 years of Quantum Physics, this is a fun account of the famous Davisson-Germer experiment that was the first to demonstrate the wave-like nature of electrons.

It's interesting that, at the end of the article, it was pointed out that this experiment did not originally was set out to seek the experimental evidence for the wave-like nature of electrons. They were intended to do something else, and then learned about something, and adapted it later. This is not really that unusual. The first thing that popped into my head was the discovery of the cosmic microwave background (CMB) by Wilson and Penzias. They certainly were not looking for the CMB with their microwave antenna. It was a serendipitous discovery. In fact, one can even say that the discovery of superconductivity also came out of an experiment that was not designed to look for it, because no one knew at that time that such a thing could exist.

One could say that this is another one of those "Who Ordered That" scenario.

Zz.

5 Physics Equations Everyone Should Know

2025-01-24T09:52:00.000-06:00

Rhett Allain posted this article on Wired on the 5 physics equation that "everyone" should know. They are, in the order that was presented:

Newton's 2nd Law of motion
The wave equation
Maxwell's equations (he cheated a bit because this is a set of 4 equations)
Schrodinger's equation (natch!)
Einsten's energy-mass equivalence equation

You can read the article to see what he has to say about each. I'm going to show this article to my students and see what they think, or maybe ask the how many of these do they think we will encounter in the course.

Zz.

Double Slit Ahead of Single Slit?

2024-04-18T13:24:00.004-05:00

This is similar to my earlier query regarding the sequence of topics that are introduced. My earlier post was the order of introducing the concept of energy and the concept of momentum. In this post, it is the issue of the sequence of introducing the double slit interference ahead of the single-slit diffraction.

This sequence is done in Knight's text "Physics for Scientists and Engineers". I don't follow that sequence because I prefer to introduce the single-slit diffraction first, show the diffraction pattern, and then introduce the double slit. The fact that the double slit pattern has interference pattern inside a single-slit diffraction envelope is easier to explain after the students already know about the single-slit diffraction.

What do you think? How did you teach this topic, or how did you learn this topic?

Zz.

Livestream of Total Solar Eclipse 2024

2024-04-06T09:00:00.007-05:00

The US National Science Foundation (NSF) will be livestreaming the total Solar Eclipse of 2024. Here is the blurb from them:

Don't just watch the eclipse — explore it. On April 8, the U.S. National Science Foundation and the NSF National Solar Observatory are hosting an educational livestream all about the science of the sun.

The livestream is a free resource that educators can use in their classrooms to share the excitement of science.

You'll hear from scientists about the unique experiments happening during the eclipse. As we count down to the moment of totality, you'll learn about:

The different layers of the sun, from the core to the corona.
The world's largest, most advanced solar telescope.
How massive solar eruptions generate space weather.

It all happens on YouTube on April 8 starting around 11 a.m. PDT/noon MDT/1 p.m. CDT/2 p.m. EDT.

https://www.youtube.com/live/qAZmtbTTQAE?si=AKttYJOJT32g-Q3O

Doppler Ultrasound Uses Confusing Color Scheme

2024-04-05T08:56:00.001-05:00

In my algebra-based General Physics courses, I get many Biology/Pre-med/Life Science majors, so of course many of the examples that I choose tend to be related to those areas. When we cover traveling waves and Doppler effect, I dive into medical diagnostics to show a few of the applications of Doppler effect in that area.

Interestingly enough, in Doppler Ultrasound, the color scheme that they use tend to be a bit confusing with what we use in physics. In the Doppler effect, when the source of a wave, or the source that is reflecting the wave, is moving away from the observer, the wavelength will be longer than the original wave. We popularly say that the wave has been "redshifted". This is because in the visible spectrum, the longest wavelength is toward the red color.

Conversely, if the object is moving toward the observer, then the wavelength will be shortened, and thus, "blueshifted", since blue (or violet) is the shortest wavelength in the visible spectrum.

But this is not the color scheme adopted in the field of Doppler Ultrasound, as represented in this video:

It seems that if the flow is toward the transducer, it is given the red color while if the flow is going away from the transducer, it is given a blue color.

Obviously, this is not a source of confusion for people in that field since they don't normally encounter those color-shifted lexicon, but for students who are studying this topic for the very first time, this takes a bit of an effort to make sure they do not become confused with the contradicting color scheme. The first time I used the Doppler ultrasound example was, unfortunately, right after I discussed an example from astronomy where I indicated that most of the light from the galaxies are redshifted and thus, a strong evidence that the universe is expanding since those galaxies are moving away from us. You can imagine that the students who were paying attention got a bit confused because the blood flowing away from the transducer is now being labeled with blue color instead of red.

Does anyone know why this field adopts this color scheme?

Zz.

AI Will Pick Nobel Prize Winners in Physics

2024-04-01T10:19:00.003-05:00

Please read the article carefully before you freak out. Hint: look at the date.

Zz.

What's In A Physics Word?

2024-04-01T10:14:00.004-05:00

This is a rather fun article in this week's Nature. It reveals some of the fascinating origin of words used in Physics and how they may not match the more common usage of the word.

All of us in physics (and in science) know of this, where we may use the same words that are used in everyday language, but they have very different meanings in physics. Unfortunately, for many people outside of physics, this can lead to a lot of confusion or misuse if they do not investigate or understand the meanings of those words as used in the context of physics. The word "spin" comes to mind when talking about the quantum spin of elementary particles.

My Favorite Web Application - Part 8

2024-03-29T10:13:00.004-05:00

My favorite web applications - Part 1

My favorite web applications - Part 2

My favorite web applications - Part 3

My favorite web applications - Part 4

My favorite web applications - Part 5

My favorite web application - Part 6

My favorite web application - Part 7

This is another one of my favorite web application because it has a ability to assign random values to various parameters in the problem.

This is a simulation of a motional emf in the form of a rail gun. It actually is a straight-forward application of magnetic force acting on a straight current. One may also solve this using Faraday's law, but it is not as straight-forward to solve because the magnetic flux (or rather, the area) does not change uniformly since the rod is accelerating.

What I also like about this simulation is that one can also tie in with what the students learned in Physics 1, i.e. they may verify their answer using kinematics, since we know the rod's mass, and it starts moving from rest. Knowing how far it travels and a good estimate of the time of travel gives us the value of the acceleration, and thus, the force acting on the rod. This should match with the magnetic force.

Zz.

I Baked Cookies For My Students

2023-09-26T15:24:00.002-05:00

A while back, I wrote an article on how to impress upon the students of the need have units in most of the numbers that they write in physics. I gave them a recipe for a banana bread, but I left out all the units of measure. It was the students themselves who noticed what was wrong with the recipe, so in the process, I managed to convey to them that (i) without units, these numbers are meaningless and (ii) this is not just something in physics (or science) but rather something common that we encounter and take for granted.

Over the Summer, I did the same thing but I showed them a recipe for my often-requested Chewy Oatmeal Cranberry cookies. Same reaction. But the difference happened at the end of the arduous and intense 8-week summer session. On the 2nd to last day of the class (last day was the final exam), after we did our review, I showed them again the cookie recipe and asked them if they remembered why I was showing them the recipe. All of them did.

I then whipped out a container that had the very same cookies, from the recipe, that I had baked the day before. Oh yeah, they were pleasantly surprised! We basically came full circle, and had a lovely time the last 15 minutes of class time as we sat around chatting and munching on the cookies. Even the coffee machine was nearby and a few of us got some coffee to go along with the cookies.

It was a wonderful end to the class, in my opinion. I am considering this Fall semester if I want to do that again. I just might, if I can find the time.

Zz.

The Unseen Impact of Physics In Healthcare

2023-07-28T07:57:00.007-05:00

This is a nice news article that provides a basic summary of the applications of physics in healthcare and medicine. It's another one of those where if someone thinks physics only deals with esoteric and useless ideas, show him/her this. I've mentioned many examples of similar medical/health/etc. applications and concepts that came directly from physics, such as this one.

As someone who often teaches general physics to life science/premed/bio/kinesiology major, this is definitely another useful evidence to get them to realize that the physics class they are taking has a direct relevance to their area of study.

Zz.

Since When Does A "Proposal" Become "Evidence"?

2023-07-14T06:49:00.002-05:00

It's one of the reasons why I groan at popular media's reporting of science.

This article is reporting on a paper that proposes a possibility of finding evidence of large-scale symmetry breaking from the data ".. in current and upcoming surveys such as those undertaken by Dark Energy Spectroscopic Instrument, the Euclid satellite, and the Vera C. Rubin Observatory.... ". Yet, the article is trumpeting the "Incredible new evidence...." as if it has been found. This is similar to accepting speculation as the truth.

Over-selling and over-hyping science does no one any good, other than making it a click-bait.

The First 12 Months of the James Webb Space Telescope

2023-07-14T06:28:00.003-05:00

Many of us knew that it would be a significant instrument. We just didn't know that in its early days, it would make this many discoveries.

In case you were asleep for most of the past 12 months, here is an article that will highlight some of the groundbreaking discoveries made by the JWST. It will not be hard to guess that there will be more earth-shattering (universe-shattering?) discoveries to be made in the next 12 months.

Zz.