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Colloquium – Marzieh Kavand – Spin Physics for Quantum Systems Applications
April 6 @ 3:30 pm - 5:00 pm
Speaker: Dr. Marzieh Kavand of Ohio State University
Title: “Studying Spin Physics in 2D Materials and Organic Semiconductors for Spintronics and Quantum Systems Applications”
Atomic size defects in solid-state materials are a material platform for spin qubits. Electrical activation of atomic size defects offers more flexibility in quantum spin devices. Tunnelling current in tunnel junction devices can be utilized as a sensitive probe of the charge and spin states. In the first part of the talk, I will introduce a tunnel junction device with an insulating layer of a hexagonal Boron Nitride (hBN). The differential current of the hBN tunnel junction devices probe signatures of the defect-assisted tunnelling in different hBN sources. These native defect states are due to lattice deformation and quality of hBN materials. Doping hBN with Carbon intentionally during its growth introduces specific atomic defects in hBN, which are then observed in the differential current response of the device. The line-shape of the peaks in the differential tunnelling current spectra broadens with the temperature increase, which is consistent with tunnelling through atomic defects.
In the second part of my talk, I will introduce pulsed electrically detected (pEDMR), and optically detected (pODMR) magnetic resonance spectroscopy techniques to study spin-dependent electronic processes in organic electronic devices. In an organic light emitting diode (OLED), there are two types of processes that control the current and electroluminescence. One type is pure single-carrier spin-dependent transport processes. The other type is spin-dependent electron-hole recombination which determines the electroluminescence yield and modulates the current. It is not straightforward to differentiate between these two types. I will discuss the correlation between the dynamics of spin-dependent electric current and spin-dependent electroluminescence in an OLED using simultaneously measured pEDMR and pODRM. This experimental approach requires careful analysis of the transient response functions under optical and electrical detection. At room temperature and under bipolar charge-carrier injection conditions, a correlation of the pEDMR and the pODMR signals is observed, consistent with the hypothesis that the recombination currents involve spin-dependent electronic transitions.