Terahertz Spectroscopy and Low Temperature Physics research (http://kbfi.ee/thz) leader is Dr. Toomas Rõõm and current projects are as follows:
1.How do chiral superconductors break time-reversal symmetry? – Kerr spectroscopy study. ERC885413
Project duration: 01.07.2021-30.06.2026
PI: dr Girsh Blumberg
Unconventional superconductivity is extensively sought for in contemporary research. Of particular interest are chiral superconductors which possess non-trivial topological properties resulting in superconducting (SC) order parameters (OPs) that may break time-reversal symmetry (TRS). The possibility of applications to topological quantum computation have placed such materials at the forefront of condensed matter research. Recent measurements of the polar Kerr effect (PKE), in which a rotation of polarization is detected for a beam of light reflected from the surface of a superconductor, have emerged as a key experimental probe of TRS breaking. Here we propose the development of a new generation of spectroscopic instrumentation for the PKE spectroscopy in the sub-THz frequency range, the energy scale that is comparable with the SC gap magnitude of unconventional superconductors. The THz range PKE spectroscopy will enable to study the broken symmetries, the origin of unconventional pairing, the in-gap collective modes, and the structures of the SC OPs. We plan to measure the PKE at sub-THz frequencies and with sub-milli-radian angular resolution from a variety of unconventional superconductors that are cooled to 100 mK, deep into SC state. The aim is to understand the basic mechanisms leading to unconventional superconductivity in these systems in order to find answers to the fundamental questions, such as: What is the structure of the SC gap in Sr2RuO4, URu2Si2, and UPt3? Is the TRS broken in (a) the Hidden Order state and in (b) SC state of URu2Si2? Which symmetries are broken at the transition from the HO state into the unconventional SC state? – and to elucidate the microscopic origin of superconductivity in the new families of unconventional superconductors. In a broader view, the project will keep Estonian physics on the forefront of science through new scientific contacts and will promote physics education by engaging students and postdocs in the research.
2. Sub-THz range polar Kerr spectroscopy of chiral superconductors, PRG736
Project duration: 01.01.20 – 31.12.24
Principal Investigator: Dr. Urmas Nagel
We propose the development of a new generation of spectroscopic instrumentation for the polar Kerr angle spectroscopy in the sub-THz frequency range that is comparable to the gap magnitude of many unconventional superconductors. Unconventional superconductivity is an active field of condensed matter research, where the theoretical models can be experimentally differentiated by the predictions they make for the symmetries of the superconducting order parameter. Interesting to us chiral superconductors possess non-trivial topological properties resulting in superconducting order parameters that may break time-reversal symmetry, and that can experimentally detected by measuring the polar Kerr angle. The samples will be cooled to about 0.1K.
Link to ETIS here.
3. Emerging orders in quantum and nanomaterials (EQUiTANT), Centre of Excellence TK134
Project duration: 01.08.15 – 31.08.23
Principal Investigator: Dr. Urmas Nagel
This CER aims to explore the new materials of various ferroic materials and their potential applications in a comprehensive way in collaboration of research groups from two universities and a research institute. Each group has PhD students who will benefit from the collaboration in the CER, by being able to set more advanced and complicated research targets, by gaining access to different experimental techniques, including large scale facilities like the European Magnet Lab or neutron facilities, but also making better use of the Estonian Magnet Lab and the Laboratory of Thin Film Technology at the University of Tartu. The high level of existing research groups will be enhanced by joint research on complex topics and thus the Estonian academic community will be stronger and more visible, both in the country and also worldwide. We will obtain the ability and skills to synthesize magnetoelectric nanomaterials that will open new possibilities for science and technology in Estonia.
Link to ETIS here.
Finished projects here.
