Autti S, Heikkinen P J, Nissinen J, Mäkinen J T, Volovik G E, Zavyalov V V, Eltsov V B
Low Temperature Laboratory, Department of Applied Physics, Aalto University, POB 15100, FI-00076, Aalto, Finland.
Department of Physics, Lancaster University, Lancaster, LA1 4YB, UK.
Nat Commun. 2022 Jun 2;13(1):3090. doi: 10.1038/s41467-022-30783-w.
A time crystal is a macroscopic quantum system in periodic motion in its ground state. In our experiments, two coupled time crystals consisting of spin-wave quasiparticles (magnons) form a macroscopic two-level system. The two levels evolve in time as determined intrinsically by a nonlinear feedback, allowing us to construct spontaneous two-level dynamics. In the course of a level crossing, magnons move from the ground level to the excited level driven by the Landau-Zener effect, combined with Rabi population oscillations. We demonstrate that magnon time crystals allow access to every aspect and detail of quantum-coherent interactions in a single run of the experiment. Our work opens an outlook for the detection of surface-bound Majorana fermions in the underlying superfluid system, and invites technological exploitation of coherent magnon phenomena - potentially even at room temperature.
时间晶体是一种处于基态周期性运动的宏观量子系统。在我们的实验中，由自旋波准粒子（磁振子）组成的两个耦合时间晶体形成了一个宏观二能级系统。这两个能级随时间演化，由非线性反馈内在地决定，使我们能够构建自发的二能级动力学。在能级交叉过程中，磁振子在朗道 - 齐纳效应与拉比布居振荡的共同作用下，从基态能级跃迁到激发态能级。我们证明，磁振子时间晶体能够在单次实验运行中展现量子相干相互作用的各个方面和细节。我们的工作为探测基础超流体系统中的表面束缚马约拉纳费米子开辟了前景，并促使对相干磁振子现象进行技术开发——甚至可能在室温下实现。
