Institut für Theoretische Festkörperphysik, JARA-FIT and JARA-HPC, RWTH Aachen University, 52056 Aachen, Germany.
Phys Rev Lett. 2014 Jan 31;112(4):046601. doi: 10.1103/PhysRevLett.112.046601. Epub 2014 Jan 29.
It is argued that the subtle crossover from decoherence-dominated classical magnetism to fluctuation-dominated quantum magnetism is experimentally accessible in graphene nanoribbons. We show that the width of a nanoribbon determines whether the edge magnetism is on the classical side, on the quantum side, or in between. In the classical regime, decoherence is dominant and leads to static spin polarizations at the ribbon edges, which are well described by mean-field theories. The quantum Zeno effect is identified as the basic mechanism which is responsible for the spin polarization and thereby enables the application of graphene in spintronics. On the quantum side, however, the spin polarization is destroyed by dynamical processes. The great tunability of graphene magnetism thus offers a viable route for the study of the quantum-classical crossover.
有人认为，在实验上可以通过石墨烯纳米带从退相干主导的经典磁性到涨落主导的量子磁性的微妙转变来实现。我们表明，纳米带的宽度决定了边缘磁性是处于经典侧、量子侧还是两者之间。在经典范围内，退相干占主导地位，导致在边缘产生静态自旋极化，这可以用平均场理论很好地描述。量子扎诺效应被确定为基本机制，它负责自旋极化，从而使石墨烯能够应用于自旋电子学。然而，在量子侧，自旋极化被动力学过程破坏。因此，石墨烯磁性的高度可调性为研究量子-经典转变提供了可行的途径。
