ABSTRACT
In 2020 a publication in Nature announced the discovery of room-temperature superconductivity in a carbonaceous sulfur hydride (CSH). The evidence for superconductivity was from resistivity and magnetic susceptibility measurements. In the figures showing the susceptibility, chi(T), "the background signal, determined from a non-superconducting CSH sample at 108 GPa, has been subtracted from the data" according to the description provided in the paper. The thus corrected susceptibility at 160 GPa (open data posted on arXiv), when displayed on an enlarged scale, exhibits a remarkable sawtooth profile which is composed of two components: chi(T) = q(T)+P(T). Here q(T) consists of integer multiples of q0 = 0.16555 nV and P(T) is a 15-node cubic spline with normal boundary conditions. These remarkable features are a shared property of the published background-corrected susceptibility data for all 6 reported pressures, however, since the160 GPa data has the biggest q0 it was noticed first for those data. Other than that, the background corrected data are completely noise-free, to the point that even the third temperature derivative of the 160 GPa data is still a smooth function. The underlying raw data (also posted on arXiv) contain considerable noise, as expected for experimental data.
In later communications some of the authors have claimed that they did not subtract a background signal at a different pressure, but used a different methodology to obtain the background corrected signal from the underlying raw data. While it is not clear how this could lead to the pathological features q(T)+P(T), it is interesting that a correlation analysis of the raw data for 160 GPa and 138 GPa indicates that those raw data also contain the steps of size q0 at the same temperatures as the background corrected data. For the other 4 pressures the noise amplitude of the raw data is too large to provide a statistically significant signature of this type.
Physics is about phenomena that can be reproduced under identical conditions. For this to be possible it is of crucial importance that scientific publications provide an accurate description of the methods of data acquisition and analysis, and of the data themselves. The issues pointed out above illustrate the importance of accurate reporting and, in view of the information reported in the paper and in later communications, motivates the question mark in the title of this presentation.
BIOGRAPHY
Prof. Dirk van der Marel received his PhD at the Univ. of Groningen in 1985. He was subsequently a Research Associate at Philips Research Eindhoven, a visiting scholar at Max Planck Institut Stuttgart (1 year) and Stanford University (1 semester), and an assistant professor at Delft University. He became a full professor at the Univ. of Groningen in 1992 and since 2003 at the Univ. of Geneva. He is now an Emeritus Professor since August 2021 after a brilliant research career in the thematics of High-Tc superconductors, Condensed Matter Physics, and infrared spectroscopy. He has been Chairman of the Condensed Matter Physics Dept., Univ. of Groningen, Director of the Condensed Matter Physics Dept., Univ. of Geneva, and President of the Physics school, Univ. of Geneva. He is also a member of the Research Council of the Swiss National Science Foundation. He is an outstanding referee of the Physical Review Journals and also received the Frank Isakson Prize of the American Physical Society.
Register in advance for this meeting:
After registering, you will receive a confirmation email containing information about joining the meeting.
*The information collected from you will be used solely for the purpose of processing your registration for the above online colloquium.
Date & Time
Venue
Chair