Since the beginning of this month, I have been in Zürich for visiting the group of Prof. Pietro Gambardella at ETH Zürich, and I am going to stay until the end of the month. The main purpose of the visit is to have in-depth discussion on the orbital transport effects in magnetic heterostructues and interfaces. For this purpose, I plan to give a serious of lectures that introduce basic concepts in this topic of research.

I already gave the first lecture on the last Friday. I covered how the atomic orbital information is described as an internal degree of freedom of Bloch states, how the crystal field potential splits the bands of Bloch states with differnet orbital characters in a specific way depending on the crystal symmetry, and what are often misunderstood regarding the orbital quenching. I also introduced minimal models for describing the orbital physics in the bulk and at the surface/interface, for which we discussed the properties of the eigenstates and eigenvalues in detail.

The lecture took more than 2 hours with lots of questions and discussions. My intention was to give a message that we need to start from fundamental principles rather than relying on our intuition which is quite bad in the orbital physics; the orbital physics has been largely overlooked because most people simply took orbital quenching from the intuition that the crystal field potential merely suppresses the orbital motion of electrons. I think my approach was quite effective, seeing the level of questions, and I hope I triggered inspirations.

The second lecture is going to be in this week, and I plan to explain the physics of orbital Hall effect. The last lecture, which is going to take place a week after, will be about how the nonequilibrium orbital angular momentum interacts with local magnetic moments.

Apart from science, I also enjoy my stay in Zürich. I find it nice to get to know new people, including those whom I have worked with in the last years, and hang out with them after work and out of the office. On the weekend, I enjoy walking along the walking trail right behind my apartment. The trail leads to the top of the hill, and from there I can see a beautiful view of the city and the lake. On this weekend, there was snow in Zürich, and it was so nice to walk under the snow. If it doesn’t snow or rain in the next weekend, I will try to go to another place in Switzerland such as Luzern.

Every week is very precious because I stay only one month. Unfortunately, I have been very busy with other works that I could not discuss as much with other colleagues as I wished. As my other works and responsibilities are getting cleared, I hope I can spend more time to discuss with others.