Ning H, Mehio O, Buchhold M, Kurumaji T, Refael G, Checkelsky J G, Hsieh D
Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125, USA.
Department of Physics, California Institute of Technology, Pasadena, California 91125, USA.
Phys Rev Lett. 2020 Dec 31;125(26):267602. doi: 10.1103/PhysRevLett.125.267602.
In the presence of electron-phonon coupling, an excitonic insulator harbors two degenerate ground states described by an Ising-type order parameter. Starting from a microscopic Hamiltonian, we derive the equations of motion for the Ising order parameter in the phonon coupled excitonic insulator Ta_{2}NiSe_{5} and show that it can be controllably reversed on ultrashort timescales using appropriate laser pulse sequences. Using a combination of theory and time-resolved optical reflectivity measurements, we report evidence of such order parameter reversal in Ta_{2}NiSe_{5} based on the anomalous behavior of its coherently excited order-parameter-coupled phonons. Our Letter expands the field of ultrafast order parameter control beyond spin and charge ordered materials.
在存在电子 - 声子耦合的情况下，激子绝缘体具有由伊辛型序参量描述的两个简并基态。从微观哈密顿量出发，我们推导了声子耦合激子绝缘体Ta₂NiSe₅中伊辛序参量的运动方程，并表明使用适当的激光脉冲序列可以在超短时间尺度上可控地反转它。通过理论与时间分辨光反射率测量相结合，我们基于其相干激发的序参量耦合声子的反常行为，报告了Ta₂NiSe₅中这种序参量反转的证据。我们的论文将超快序参量控制领域扩展到了自旋和电荷有序材料之外。
