von Witte Gevin, Kozerke Sebastian, Ernst Matthias
Institute for Biomedical Engineering, University and ETH Zurich, 8092 Zurich, Switzerland.
Institute of Molecular Physical Science, ETH Zurich, 8093 Zurich, Switzerland.
Sci Adv. 2025 Jan 3;11(1):eadr7168. doi: 10.1126/sciadv.adr7168.
Dynamic nuclear polarization (DNP) and emerging quantum technologies rely on the spin transfer in electron-nuclear hybrid quantum systems. Spin transfers might be suppressed by larger couplings, e.g., hyperfine couplings suppressing nuclear dipolar flip-flops ("spin diffusion barrier"). We apply the Schrieffer-Wolff transformation to a two-electron two-nucleus spin system involving dipolar and hyperfine couplings in their tensorial form and study possible polarization-transfer processes. Among the different effective Hamiltonian matrix elements investigated is an energy-conserving electron-nuclear four-spin flip-flop, which combines an electronic with a nuclear dipolar flip-flop. The relevance of this electron-nuclear four-spin flip-flop for nuclear spin diffusion close to electrons is supported by model fits of HypRes-on experimental data. We connect the closely related fields of magnetic resonance and quantum information and provide a model that explains how all nuclear spins can contribute to the hyperpolarization of the bulk without a spin diffusion barrier in DNP.
动态核极化（DNP）和新兴量子技术依赖于电子 - 核混合量子系统中的自旋转移。自旋转移可能会被更强的耦合所抑制，例如超精细耦合抑制核偶极翻转（“自旋扩散屏障”）。我们将施里弗 - 沃尔夫变换应用于一个包含张量形式的偶极和超精细耦合的双电子双核自旋系统，并研究可能的极化转移过程。在所研究的不同有效哈密顿矩阵元中，有一种能量守恒的电子 - 核四自旋翻转，它将电子偶极翻转与核偶极翻转结合在一起。HypRes-on实验数据的模型拟合支持了这种电子 - 核四自旋翻转对靠近电子处核自旋扩散的相关性。我们将磁共振和量子信息这两个密切相关的领域联系起来，并提供了一个模型，该模型解释了在DNP中所有核自旋如何在没有自旋扩散屏障的情况下对整体的超极化做出贡献。
