同位素富集硅-28晶体中光学超极化磷施主核的感应测量
Inductive measurement of optically hyperpolarized phosphorous donor nuclei in an isotopically-enriched silicon-28 crystal
摘要：
我们在实验上证明了在同位素富集的硅-28晶体中的光学超极化磷-31供体核自旋的感应读出。晶体中磷供体的浓度为1.5 × 10 $^{15}$ cm $^{-3}$，比先前通过直接感应检测检测到的低三个数量级。在来自1 cm $^3$样品（$\approx 10^{15}$自旋）的单个自由感应衰减中测量的信噪比为113。通过将样品转移到X波段ESR谱仪，我们能够获得在1.7 K的64%的核自旋极化的下限。在1.7 K下，用Hahn回波序列测量的$^{31}$ P-T $_{2}$为420 ms，用Carr Purcell循环将其延长至1.2 s。$^{31}$ P核自旋在1.7 K时的T $_1$非常长，无法确定，因为即使在4.5小时的时间尺度上也没有观察到衰变。用1047 nm激光器进行光激发，其提供硅的带隙以上激发。在4.2 K下的超极化的建立遵循单指数的特征时间为577 s，而在1.7 K下的建立表现出双指数行为的特征时间常数为578 s和5670 s。
英文摘要：
We experimentally demonstrate the inductive readout of optically hyperpolarized phosphorus-31 donor nuclear spins in an isotopically enriched silicon-28 crystal. The concentration of phosphorus donors in the crystal was 1.5 x 10$^{15}$ cm$^{-3}$, three orders of magnitude lower than has previously been detected via direct inductive detection. The signal-to-noise ratio measured in a single free induction decay from a 1 cm$^3$ sample ($\approx 10^{15}$ spins) was 113. By transferring the sample to an X-band ESR spectrometer, we were able to obtain a lower bound for the nuclear spin polarization at 1.7 K of 64 %. The $^{31}$P-T$_{2}$ measured with a Hahn echo sequence was 420 ms at 1.7 K, which was extended to 1.2 s with a Carr Purcell cycle. The T$_1$ of the $^{31}$P nuclear spins at 1.7 K is extremely long and could not be determined, as no decay was observed even on a timescale of 4.5 hours. Optical excitation was performed with a 1047 nm laser, which provided above bandgap excitation of the silicon. The build-up of the hyperpolarization at 4.2 K followed a single exponential with a characteristic time of 577 s, while the build-up at 1.7 K showed bi-exponential behavior with characteristic time constants of 578 s and 5670 s.
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