This blog contains thoughts and observations on a wide range of physics related topics that I find interesting and which I believe are worthwhile sharing. My goal is to create one new entry every month. Some of the entries are rather opinionated and I'm always happy to discuss them in more depth. Feel free to send me an email for further discussion, and of course also if you find any mistakes: stefan.kehrein@theorie.physik.uni-goettingen.de

There is a remarkable connection between geophysics, namely so called Kelvin and Yanai waves, and topological materials. Kelvin and Yanai waves are regular and stable, always travel eastward around the equator and are important for weather phenomena like El Niño. In two papers Delplace et al. and Xu et al. show that the equator as the boundary between the northern and southern hemisphere plays the role of a boundary in a topological material: The Coriolis force acts like the magnetic field in a quantum Hall device and the equatorial waves are the topologically protected currents at the boundary. The stability of Kelvin and Yanai waves is therefore rooted in nontrivial topological winding numbers that can be defined in frequency-wavevector space, and have actually been experimentally confirmed after their theoretical prediction. Truly remarkable.

The Ranga Dias scandal is a disturbing tale of scientific misconduct. Starring prominently is Nature and its publishing policies. At the center of this scandal are experiments done in Ranga Dias' lab at the University of Rochester on high-temperature high pressure superconductivity. This is an established (experimentally very challenging) field with the ultimate goal of realising superconductivity at room temperature under high pressure. In 2020 the Dias group published a Nature article claiming room temperature superconductivity at 270 GPa in carbonaceous sulfur hydride (CSH). There were immediate concerns regarding the validity of the experimental data, and after significant back and forth the paper was retracted by Nature in 2022 against the express will of its authors. Against this background Dias et al. submitted another even more spectacular manuscript to Nature in 2022, claiming room temperature superconductivity at just 10kbar in doped lutetium hydride (LuH). Under the veil of "decisions should be made on the basis of the scientific quality, not who the authors are" (quote from Magdalena Skipper, Nature’s editor-in-chief, source) the manuscript was accepted and published in 2023 in spite of the fact that only one out of four referees said that there was solid proof of superconductivity (source). Again there was immediate concern in the community, which led to numerous rounds of investigations at the University of Rochester. The first three rounds found no misconduct, until the genius decision was made to also interview the students involved in the experiment in round four. Then the whole thing fell apart because the students could not connect the published data with their actual measurements. Eventually the LuH manuscript was retracted by Nature in 2023.

One can learn some important lessons from this story. Like: Spectacular claims need spectacular proofs. And: If in doubt ask the students. It remains to be seen to what extent these lessons have been learned when they next collide with commercial interests.

For more background reading I recommend Physik Journal 23 (2024), p. 22 [german] and the investigation reports by Nature from 2024: Superconductivity scandal: the inside story and Exclusive: official investigation reveals how superconductivity physicist faked blockbuster results.