Weblog Yuli Nazarov
Fifth lecture Advanced Quantum Mechanics
I took time slot of a Thursday problem-solving session. This was mostly to achieve a better synchronization between the lectures and PPS. Unfortunate effect on this is that the students are bored with my face since I show up too often. So I was told by my colleagues. I have to believe in this since I myself is seldom bored with my own face.
Anyway, this was my favorite topic(s): superconductivity and superfluidity. I enjoyed talking and told at least three “side” stories, in particular, the legend about Leiden street boy. I think I could do all important things on time.
There was a question about some skipped algebra in the break. I always get confused with such questions and perhaps did not react adequately. Actually, for all twenty years I’m giving the lectures I never managed to derive for myself a golden rule that would automatically tell me how much derivations I need to hide. So I always remain in a stressfull balance between “…substitute zis to zis and see how beautiful is the cancellation of factors of 2 in the numerator and denominator…” and “as, you know, you can easily see …” Between Scylla and Charybdis is my endless way 🙂
Fourth lecture Advanced Quantum Mechanics
We got through the formal part of the course – and started enjoying the examples! Magnetism, the puzzle of centuries:) I’ve put quite some new material I’ve never taught before. This was about magnons and other excitations in a magnet. I was not sure I could do it in time from the first attempt and warned the students in the beginning that perhaps I will have to skip this part.
Well, it went better than expected, though I had to skip a couple of slides. Moreover, it looks I could catch an attention provoking questions. The idea of the energy splitting of two spin subbands has spontaneously originated in the audience, a way before I was planning to talk about it. Nice 🙂
Anyway, there is room for improvement for the next time.
Third lecture Quantum Transport
was half-inteference, half-restoration of Ohm’s law – I still keep half-lecture shift. The advantage of this was that I could repeat the double junction that plays a key role in both topics. It occurred to me that the audience was more active than in former years at the interference part – good, but less active for Ohm’s law. Was I too monotonic for the second half of the lecture or the student’s tastes fluctuate from year to year?
Exact correspondence
Me and Mohammad Ansari have submitted a paper that concludes a nice piece of research on Renyi entropies. We have found an exact relation, like fluctuation-dissipation theorem, that relates physical and unphysical quantities: you can guess the implications:))))
Exact correspondence between Renyi entropy flows and physical flows
Mohammad H. Ansari, Yuli V. Nazarov
We present a universal relation between the flow of a Renyi entropy and the full counting statistics of energy transfers. We prove the exact relation for a flow to a system in thermal equilibrium that is weakly coupled to an arbitrary time-dependent and non-equilibrium system. The exact correspondence, given by this relation, provides a simple protocol to quantify the flows of Shannon and Renyi entropies from the measurements of energy transfer statistics.
Problem-solving session AQM
Neither Michael nor Albert could help me on this day: I had to do PSS myself. Fortunately all students were in place with the presentations and spoke sense. I also gave some practical advices on second-quantization calculations: hope it works. Besides, I asked students to fill in a survey about the course. I will investigate the data collected and present the results on next week.
Isaiah 2:4
read this on Wednesday in attempts of improving my spiritual life 🙂
And he shall judge among the nations, and shall rebuke many people: and they shall beat their swords into plowshares, and their spears into pruning hooks: nation shall not lift up sword against nation, neither shall they learn war any more.
Well, this hardly worked. Instead of enlightening, I felt irritation and anger. Say, 20 years ago this citation seemed to be not far from the realization. Nowadays Evil rises head again: it does so in most stupid, shameless and hypocritical fashion. Who is sillier: people raging for arms or me with my optimistic beliefs?
Third lecture Advanced Quantum Mechanics
was the core of the course: second quantization. It was pretty formal, though I did my best to outline the logics and motivation behind the formulas. The students were warned that it will be boring, so they remain rather accepting. I went slower trying to establish better contact. This resulted in a time problem: in fact, I said only few most important things about fermion quantization. Luckily, it is almost the same as for bosons.
Second lecture Quantum Transport
was on Friday. I was supposed to start with the interference. However, there was a sweet topic of counting statistics left from the first lecture. Since I liked the topic, and since one needs to brush some probability analysis to understand the issue, it went slower than expected. So I’ve managed to do only a half of the interference lecture. Well, this is rather inconvenient – to have a half-lecture shift, but I do not want at the moment to make the shift integer 🙂
Charles Markus
from Copenhagen, a brilliant experimentalist who has now mostly concentrated on Majoranization of semiconducting nanowires by connecting those to superconductors – has given a talk on Thursday.
He started with reporting successes in nanowire growth: nanowires can be better contacted with superconductors, and can be made in t and h shapes. He has shown “hard gap” – looked good, finally in place after years of technological search.
Then we got the report on experimental results – some fresh, right from the oven. The results in “Delft geometry” seemed clean but I did not quite see the gap as hard as promised. The results in “Copenhagen geometry” were a superconducting island has been attached to the nanowire seemed more fun – I will have to revise those carefully.
Wilfred van der Wiel
from Twente University gave a Nanoscience seminar on Wednesday. I vividly remember him as an outstanding PhD student, have not seen him for years and was delighted to see no significant change: in the position of full professor, he reminds sharp, handsome, nice and does outstanding research.
There were two topics. First one: Wilfred has investigated the conductance (well, if you can call inverse GigaOhm a conductance) of molecular wires thread in zeolyte crystal. The conductance could be changed by order of magnitude by tiny magnetic field in millitesla range. The mechanism of the effect must be related to nuclear spins and as such is the same as for the spin-blockade lifting in double quantum dots. The details remain unclear for me: yet the effect is there and is a record-strong.
The second topic has fascinated me even more. The physics was rather simple: Coulomb blockade in a pile of gold nanoparticles carelessly collected between a multitude of electrodes. A neat physical realization of complete and hopelessly incomprehensible mess. Yet it appears that that it is the mess that motivated the researcher. Wilfred managed to demonstrate that with the proper tuning (based on genetic algorithm) the pile can work as any of the logical gates! I reckon this work will have a big philosophical impact (seriously). It proves that electronic components can be made from anything (substitute “anything” with a stronger word if you like).