arXiv subjects

K. Saeedi

Publications and source records attributed to K. Saeedi.

3 recordsLinked to original sources

arXiv2026

FIR transmission and resistively detected cyclotron resonances in InSb

We have developed an experimental setup to simultaneously acquire magneto-transmission spectra and measure the photoconductive response. The low-temperature ($T$=4.2 K) magneto-transmission data for weakly doped InSb in the frequency range 3-15 THz and magnetic fields up to 25 T, shows that the AC conductivity is governed by the classical Drude response. Moreover, the resulting light-induced voltage in this system, consisting of thermoelectric and resistive contributions, both contain features that are related to cyclotron resonances. The frequency dependence of this resonance is in good agreement with $\mathbf{k\cdot p}$ perturbation theory and corresponds to transitions between the first and second Landau level with spin-up electrons. The obtained effective mass $m^{*}(B=0)=0.014m_{e}$, is in line with the value extracted from magneto-transmission experiments. Additionally, we can observe evidence of a fluence-dependent metal-insulator transition in the thermoelectric signal, which suggest that the electronic system becomes less sensitive to the light at higher frequencies.

cond-mat.mtrl-sci↗

arXiv2011

Optically detected NMR of optically hyperpolarized 31P neutral donors in 28Si

The electron and nuclear spins of the shallow donor 31P are promising qubit candidates invoked in many proposed Si-based quantum computing schemes. We have recently shown that the near-elimination of inhomogeneous broadening in highly isotopically enriched 28Si enables an optical readout of both the donor electron and nuclear spins by resolving the donor hyperfine splitting in the near-gap donor bound exciton transitions. We have also shown that pumping these same transitions can very quickly produce large electron and nuclear hyperpolarizations at low magnetic fields, where the equilibrium electron and nuclear polarizations are very small. Here we show preliminary results of the measurement of 31P neutral donor NMR parameters using this optical nuclear hyperpolarization mechanism for preparation of the 31P nuclear spin system, followed by optical readout of the resulting nuclear spin population after manipulation with NMR pulse sequences. This allows for the observation of single-shot NMR signals with very high signal to noise ratio under conditions where conventional NMR is not possible, due to the low concentration of 31P and the small equilibrium polarization.

physics.atom-ph↗

arXiv2010

Hyperfine structure and nuclear hyperpolarization observed in the bound exciton luminescence of Bi donors in natural Si

As the deepest group V donor in Si, Bi has by far the largest hyperfine interaction, and also a large I=9/2 nuclear spin. At zero field this splits the donor ground state into states having total spin 5 and 4, which are fully resolved in the photoluminescence spectrum of Bi donor bound excitons. Under a magnetic field, the 60 expected allowed transitions cannot be individually resolved, but the effects of the nuclear spin distribution, -9/2 <= I_z <= 9/2, are clearly observed. A strong hyperpolarization of the nuclear spin, with sign opposite to the expected equilibrium polarization, is observed to result from the nonresonant optical excitation. This is very similar to the recently reported optical hyperpolarization of P donors observed by EPR at higher magnetic fields. We introduce a new model to explain this effect, and predict that it may be very fast.

quant-ph↗