Juraschek D M, Fechner M, Spaldin N A
Materials Theory, ETH Zurich, CH-8093 Zürich, Switzerland.
Phys Rev Lett. 2017 Feb 3;118(5):054101. doi: 10.1103/PhysRevLett.118.054101. Epub 2017 Jan 31.
We describe a mechanism by which nonlinear phononics allows ultrafast coherent and directional control of transient structural distortions. With ErFeO_{3} as a model system, we use density functional theory to calculate the structural properties as input into an anharmonic phonon model that describes the response of the system to a pulsed optical excitation. We find that the trilinear coupling of two orthogonal infrared-active phonons to a Raman-active phonon causes a transient distortion of the lattice. In contrast to the quadratic-linear coupling that has been previously explored, the direction of the distortion is determined by the polarization of the exciting light, introducing a novel mechanism for nonlinear phononic switching. Since the occurrence of the coupling is determined by the symmetry of the system we propose that it is a universal feature of orthorhombic and tetragonal perovskites.
我们描述了一种机制，通过该机制非线性声子学能够对瞬态结构畸变进行超快相干和定向控制。以ErFeO₃作为模型系统，我们使用密度泛函理论来计算结构性质，并将其作为输入，用于描述系统对脉冲光激发响应的非简谐声子模型。我们发现，两个正交的红外活性声子与一个拉曼活性声子的三线性耦合会导致晶格的瞬态畸变。与之前研究的二次 - 线性耦合不同，畸变的方向由激发光的偏振决定，这引入了一种用于非线性声子开关的新机制。由于耦合的发生由系统的对称性决定，我们提出这是正交和四方钙钛矿的普遍特征。
