Chen Shao-Wen, Liu Ren-Bao
Department of Physics, Centre for Quantum Coherence, & Institute of Theoretical Physics, The Chinese University of Hong Kong, Hong Kong, China.
Sci Rep. 2014 Apr 15;4:4695. doi: 10.1038/srep04695.
Central spin decoherence is useful for detecting many-body physics in environments and moreover, the spin echo control can remove the effects of static thermal fluctuations so that the quantum fluctuations are revealed. The central spin decoherence approach, however, is feasible only in some special configurations and often requires uniform coupling between the central spin and individual spins in the baths, which are very challenging in experiments. Here, by making analogue between central spin decoherence and depolarization of photons, we propose a scheme of Faraday rotation echo spectroscopy (FRES) for studying quantum fluctuations in interacting spin systems. The echo control of the photon polarization is realized by flipping the polarization with a birefringence crystal. The FRES, similar to spin echo in magnetic resonance spectroscopy, can suppress the effects of the static magnetic fluctuations and therefore reveal dynamical magnetic fluctuations. We apply the scheme to a rare-earth compound LiHoF4 and calculate the echo signal, which is related to the quantum fluctuations of the system. We observe enhanced signals at the phase boundary. The FRES should be useful for studying quantum fluctuations in a broad range of spin systems, including cold atoms, quantum dots, solid-state impurities, and transparent magnetic materials.
中心自旋退相干对于探测环境中的多体物理是有用的，此外，自旋回波控制可以消除静态热涨落的影响，从而揭示量子涨落。然而，中心自旋退相干方法仅在某些特殊配置下可行，并且通常需要中心自旋与热库中各个自旋之间的均匀耦合，这在实验中极具挑战性。在此，通过建立中心自旋退相干与光子退极化之间的类比，我们提出一种用于研究相互作用自旋系统中量子涨落的法拉第旋转回波光谱（FRES）方案。光子偏振的回波控制通过用双折射晶体翻转偏振来实现。FRES与磁共振光谱中的自旋回波类似，可以抑制静态磁涨落的影响，从而揭示动态磁涨落。我们将该方案应用于稀土化合物LiHoF4并计算回波信号，该信号与系统的量子涨落有关。我们在相边界处观察到增强的信号。FRES对于研究包括冷原子、量子点、固态杂质和透明磁性材料在内的广泛自旋系统中的量子涨落应该是有用的。
