IMPORTANT METROLOGY PRIZE AWARDED TO RESEARCH GROUPS FROM PTB AND FROM BERLIN/FREIBURG
From fundamental physics related to Einstein's special theory of relativity to fundamentals of metrological applications in the range of thousandths of micrometers (i.e. nanometers) – the bandwidth of this year's Helmholtz Prize is considerable. The Helmholtz Prize, which recognizes outstanding scientific and technological research in the field of "precision measurement in physics, chemistry and medicine", is awarded every second year. Three scientists have been awarded the prize in the category of “fundamental research” for their work at PTB. By means of a long-term comparison between two highly accurate clocks (optical ytterbium clocks) of PTB, Christian Sanner, Nils Huntemann and Richard Lange have succeeded in considerably improving the procedure to test the fundamental symmetry of space (Lorentz symmetry) for electrons. The Helmholtz Prize in the category of “applied metrology” has been awarded to a team consisting of nine researchers from the Humboldt-Universität zu Berlin and from the University of Freiburg (Albert-Ludwigs-Universität Freiburg) working with Saskia F. Fischer, a physicist, and Peter Woias, a microsystems expert. This group has also broken new ground by laying down the scientific and technical prerequisites to standardize the measurement of individual nanostructures. In metrology (the science of precise measurement), the Helmholtz Prize is considered one of the world’s most prominent distinctions. The prize is awarded in two categories – "fundamental research" and "applied metrology" – and includes 20 000 euros in prize money for each of the two categories.
Testing the symmetry of space-time by means of atomic clocks
The team from PTB has addressed a fundamental question of physics. One of the basic assumptions of Einstein’s special theory of relativity is that the speed of light is always the same, independent of its direction of propagation. Now we may ask ourselves: How universal is this symmetry of space, also known as Lorentz symmetry? Does it apply equally to the motion of particles of matter like electrons, or are there any directions along which these particles move faster or more slowly at the same energy? In particular, for high energies of the particles, theoretical models of quantum gravitation predict a violation of Lorentz symmetry. These models are designed to provide a unified description of the smallest (i.e. the quantum) world, with gravity that we typically observe between celestial bodies. Optical spectroscopy of atomic transitions, which is the study of the interaction between light and atoms, offers a unique level of precision. This enables stringent tests of the fundamental assumptions and predictions of the theory of relativity. In 2016, PTB physicists presented a clock based on the interaction of high-precision laser light with a single Yb+ atom and achieved a relative accuracy of 3 × 10-18. If this clock had started ticking at the time of the Big Bang (13.7 billion years ago), it would now be one second out of sync. Two versions of this optical Yb+ clock in different spatial orientations are being used to test Lorentz symmetry with unprecedented accuracy.
In a universe that obeys the laws of Lorentz symmetry (as assumed in the theory of relativity), a physical experiment must always yield the same result, independent of its orientation in space or its uniform motion. But can we be sure that this symmetry is maintained up to the limits of what Yb+ clocks can measure? Building on the tradition of the Michelson-Morley experiments (first performed more than 100 years ago), Christian Sanner, Nils Huntemann and Richard Lange succeeded in improving the limits for a violation of Lorentz symmetry for electrons by two orders of magnitude. As a “side-effect” (but an important one), their long-term comparison has confirmed the extremely small systematic uncertainty of the two optical Yb+ clocks, which amounts to less than 4 × 10-18. The results were published in Nature.
A new path to standardized nanometrology
The 2020 Helmholtz Prize in the category of "applied metrology" was awarded to a team of scientists from the Humboldt-Universität zu Berlin and from the University of Freiburg. Maximilian Kockert, Danny Kojda, Rüdiger Mitdank, Anna Mogilatenko and Saskia F. Fischer (Humboldt-Universität Berlin), and Zhi Wang, Johannes Ruhhammer, Michael Kröner and Peter Woias (University of Freiburg) have succeeded in developing the first standardizable procedure to measure structures in the nanometer range (thousandths of micrometers).
The problem with nanostructured materials is that they often have properties that are completely different from those of macroscopic materials. In the nanometer range, besides the type of material, the form of surfaces – i.e., their geometric dimensions and surface texture – plays a key role. The motto for industrial design and architecture coined a hundred years ago in connection with the Bauhaus school – “form follows function” – no longer applies in the nanometer range. Often, this motto must even be turned on its head for parameters of nanostructured materials – “form defines function”. This allows the material properties to be customized in terms of their shape. It is therefore even more important to be able to measure these material parameters accurately and reliably, which presents metrology with a challenge.
In their work, the team of researchers presented standardizable precision measurements of the Seebeck coefficient; the scope of these measurements can be extended from their model system (silver wires with a diameter in the nanometer range and a single-crystalline structure) to cover other nanostructures and additional parameters. The researchers have thus demonstrated that standardized high-precision measurements over a wide temperature range are possible for comprehensive thermoelectric characterization (i.e., when measuring electrical conductivity, thermal conductivity and the Seebeck coefficient), even for metallic nanomaterials. Their results were published in Scientific Reports.
The Helmholtz Prize is awarded by the Helmholtz Fund for outstanding scientific and technological research in the field of "precision measurement in physics, chemistry and medicine" in the categories of "fundamental research" and "applied metrology".
2020 Helmholtz Prize for precision measurement in fundamental research
Dr. Christian Sanner (PTB, currently working at JILA in Boulder, CO, USA), Dr. Nils Huntemann and Richard Lange (both from PTB)
for their work titled "Single-atom spectroscopy with eighteen-digit accuracy to measure the symmetry of space-time"
Christian Sanner, Nils Huntemann, Richard Lange, Christian Tamm, Ekkehard Peik, Marianna S. Safronova, Sergey G. Porsev: Optical clock comparison for Lorentz symmetry testing. Nature 567, 204 (2019)
Dr. Nils Huntemann, Working Group 4.43 "Optical Clocks with Trapped Ions", Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany, phone: +49 531 592-4430, e-mail: firstname.lastname@example.org
2020 Helmholtz Prize for precision measurement in applied metrology
Maximilian Kockert, Dr. Danny Kojda, Dr. Rüdiger Mitdank, Dr. Anna Mogilatenko and Prof. Dr. Saskia F. Fischer (contributed research from the Humboldt-Universität zu Berlin), and Dr. Zhi Wang, Dr. Johannes Ruhhammer, Dr. Michael Kröner and Prof. Dr. Peter Woias (contributed research from the University of Freiburg) for their work titled "Nanometrology: Absolute Seebeck coefficient of individual silver nanowires".
M. Kockert, D. Kojda, R. Mitdank, A. Mogilatenko, Z. Wang, J. Ruhhammer, M. Kroener, P. Woias, S. F. Fischer: Nanometrology: Absolute Seebeck coefficient of individual silver nanowires. Scientific Reports 9, 20265 (2019)
Prof. Dr. Saskia F. Fischer, Humboldt-Universität zu Berlin, Department of Physics, WG Novel Materials, Newtonstraße 15, 12489 Berlin phone: +49 30 2093-8044, e-mail: email@example.com
Prof. Dr. Peter Woias, University of Freiburg, Department of Microsystems Engineering (IMTEK), Laboratory for the Design of Microsystems, Georges-Köhler-Allee 102, 79110 Freiburg, phone: +49 761 203-7490, e-mail: firstname.lastname@example.org