Observation of novel nuclear spin dynamics of phosphorus-doped silicon : $^{31}P$ NMR = 인이 첨가된 실리콘에서 새로운 핵스핀 동역학 관찰 : 인 핵자기공명$^{31}P$ NMR

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Phosphorus-doped silicon (Si:P) has attained renewed interest as a material system candidate for a solid-state quantum computer where the P donor nuclear spins with bound electrons in a magnetic field serve as qubits. To understand the mechanism how the information encoded in the qubits is preserved or lost is important to forsee a feasibility of the quantum computer or to operate the quantum computer if once built. It is essentially to understand how the nuclear and electrons spins relax and dephase through various interactions among themselves and with environment. The silicon quantum computer requrires an extreme condition of very low temperature and high magnetic field, typically below 100 mK and above 2 T, for proper initialization and operation. The study of local magnetic properties of both nuclei and electrons at the extreme comdition has thus become of great interest. The present thesis presents novel features of nuclear spin dynamics in metallic Si:P at very low temperature and high magnetic field observed by $^{31}P$ NMR method and provides some possible interpretation. The experiments have been carried out for two Si:P samples of different concentrations, $n = 1.8 \times 10^{19} cm^{-3}$ and $5.6 \times 10^{19} cm^{-3}$, at temperatures between 45 mK and 5 K in a magnetic field of 7 T. Longitudinal nuclear magnetization below 1 K when inverted by rf pulses recovers the thermodynamic equilibrium following a double-exponential function rather than a single-exponential one as usual in metals and as observed above 1 K. Two distinctive time-constants for the relaxtion can be defined, the short $T_1$ and long $T_1$. The short $T_1$ with temperature follows the Korringa`s relation for an electron gas down to 0.2 K, below which, however, it gradually deviates from the relation. These unusual relaxation behaviors can be well accounted for by considering a large nuclear Zeeman specific heat at low temperature and high field. The slow stage of the ...
Lee, Soon-Chilresearcher이순칠researcher
한국과학기술원 : 물리학과,
Issue Date
327705/325007  / 020035272

학위논문(박사) - 한국과학기술원 : 물리학과, 2009. 8., [ viii, 67 p. ]


Silicon; Quantum Computer; NMR; Spin Relaxation; Decoherence; 실리콘; 양자컴퓨터; 핵자기공명; 스핀 완화; 결흩어짐

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