On Monday, December 18, at 11.00 AM, Jerzy Pniewski and Leopold Infeld Colloquium of the Faculty of Physics will be held in room 0.06.

The lecture entitled:

"On the way to quantum ampere and quantum kilogram"

will be delivered by:
prof. dr hab. Tomasz Dietl
International Research Centre MagTop, Institute of Physics, Polish Academy of Sciences, Warsaw, Poland

Prof. Tomasz Dietl is one of the most recognized Polish scientists. He specializes in the physics of semiconductors, spin phenomena, and magnetic materials; he is co-founder of the research domain known as spintronics.
The trend in recent decades has been to redefine the units of the International System of Units so that the units refer to physical constants. (E.g. the revised, current definition of the meter refers to a physical constant in the form of the speed of light, and no longer to a standard stored at Sevres). During the lecture, we will learn what contribution the study of spin phenomena in condensed matter can make to the new definitions of the basic SI units.

The lecture will be held in English.

On the way to quantum ampere and quantum kilogram

Tomasz Dietl
International Research Centre MagTop, Institute of Physics, Polish Academy of Sciences, Warsaw, Poland
dietl@MagTop.ifpan.edu.pl

In 2019, four of the seven SI base units specified in the International System of Quantities were redefined in terms of natural physical constants rather than human artifacts such as the standard kilogram. In particular, the kilogram and ampere are now defined by setting exact numerical values for the Planck constant h and the elementary electric charge e. That redefinition was prompted by the existence of the Josephson and quantum Hall effects, making it possible to connect directly quantum fundamental constants h and e to the lab practice.
In the talk, I will present recent progress in fabricating resistance quantum Hall standards working in magnetic fields low enough to allow for integration with superconducting Josephson junctions that constitute the voltage standard. Such an integrated device establishes the ampere standard and the kilogram standard via the Kibble balance. I will emphasize the role of dilute magnetic semiconductors and our experimental [1] and theoretical [2] contributions to the field of quantum Hall resistance standards.

[1] I. Yahniuk et al., npj Quant. Mater. 4 (2019) 13; arXiv:2111.07581 (2021).

[2] T. Dietl, Phys. Rev. Lett. 130 (2023) 086202; Phys. Rev. B 107 (2023) 085421.