Master Topics 2021/2022

1) Study of molecular quantum bits by high-frequency electron paramagnetic resonance

In quantum computation the classic binary digit (bit) is replaced by a so-called quantum bit (qubit). Molecular spins are potential candidates for qubits depending on the lifetime (relaxation time) of their spin states. This property can be chemically engineered by changing organic ligands around the central metal atom. The goal of this work is the characterization of several molecular spin systems based on cobalt with different ligands using high-frequency electron paramagnetic resonance (HF-EPR) spectroscopy. This tool enables direct observation of spin transitions, and the simulation of EPR absorption spectra provides the intrinsic molecular magnetic parameters and relaxation times.

Supervisor: Dr. Vinicius Santana

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2) Digital processing of high-resolution electron paramagnetic resonance maps

In the conventional electron paramagnetic resonance (EPR) one uses the microwave excitation at a fixed frequency and sweeps the magnetic field to match the resonance condition. Modern superconducting magnets can perform slow sweeps only (0.2 – 1 T/min). In our group, we take another approach – sweeping the microwave frequency instead of the magnetic field. It allows us to acquire EPR spectra a thousand times faster. Consequently, we perform fast frequency scans during the slow sweep of the magnetic field and obtain very detailed two-dimensional (field and frequency) resonance maps (≈50000×1000 points). Unfortunately, the frequency sweeps bring undesired strong background signals and other artefacts. In this Master topic, the student will work on the digital processing of such maps to remove the background and other undesired signals.

Supervisor: Dr. Oleksii Laguta

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3) Background removal in rapid-scan electron paramagnetic resonance spectra

Investigation of electron spin dynamics is usually performed by the well-established method of pulsed electron paramagnetic resonance (EPR). However, this technique struggles from several technical difficulties when performed at the microwave frequencies above 100 GHz. In this regard, we develop a special regime of EPR which utilizes fast frequency sweeps – rapid-scan EPR. The only obstacle on the way of efficient use of rapid-scan EPR is a strong background signal which can completely bury the EPR signal. This Master topic will be devoted to the developing of algorithms for removal of this background.

Supervisor: Dr. Oleksii Laguta

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4) Investigation of impurities in semiconductor materials via frequency rapid scan electron paramagnetic resonance method

Frequency rapid scan is one of the novel methods in EPR spectroscopy, which can be used to determine relaxation time of a spin system. Unlike pulsed methods, rapid scan is not limited by dead time of detector and does not require high power microwave sources. Aim of this project is to apply a rapid scan method on high frequency EPR spectrometer to investigate impurities in semiconductors, with focus of silicon carbide.

Supervisor: doc. Petr Neugebauer

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