腾讯会议ID：679-795-660

会议密码：0506

主  持  人：任新国   特聘研究员

联  系  人：傅琦   (fuqi@iphy.ac.cn)

Abstract:
How electron spins exchange angular momentum with lattice vibrations remains a central open question, with broad implications for spin transport, decoherence, and the control of quantum states in solids. Chiral phonons, which carry angular momentum through circular or elliptical atomic motion, offer a distinct route to generate and manipulate spin polarization without magnetic fields, potentially even in materials with weak intrinsic spin–orbit coupling.

In this talk, I will present my recent first-principles theoretical work on chiral phonons in a chiral hybrid organic–inorganic perovskite and their role in nonequilibrium spin transport. Using ab initio phonon calculations and phonon angular momentum analysis, we show that low-symmetry chiral perovskites support strongly polarized acoustic chiral phonons whose net angular momentum becomes finite under a temperature gradient.

We further show that this nonequilibrium phonon angular momentum can induce measurable responses, including rigid-body rotation, weak magnetization, and spin current generation at a metal/perovskite interface. While the chiral-phonon-induced magnetic field is too weak to explain the observed spin current, we propose a microscopic Barnett effect: chiral phonon angular momentum shifts the spin-dependent chemical potential, creating an interfacial spin chemical potential gradient that drives spin current into an adjacent Cu layer. The estimated spin current is consistent with experimental observations of the chiral-phonon-activated spin Seebeck effect. Beyond interface-driven spin transport, we also show that nonlinear temperature profiles can generate intrinsic spin currents in the chiral bulk.

These results provide a microscopic picture of angular momentum transfer from chiral lattice motion to electronic spins and suggest new strategies for designing chiral materials for spin caloritronics and nonequilibrium quantum materials applications.

Brief CV of Dr. Xixi Qin:
秦茜茜现为斯坦福大学和SLAC国家加速器实验室博士后研究员，于2023年获得杜克大学博士学位。她是一名计算凝聚态理论和材料科学研究者，主要从事量子材料中非平衡电子–声子和自旋–声子动力学的第一性原理模拟研究。她的代表性工作包括以第一作者和通讯作者身份发表于 PRL，以及以共同第一作者或主要理论作者身份发表于 Nature、AFM 和 PRX Energy 等期刊。她的长期研究目标是发展可预测的第一性原理方法，建立微观电子、声子和自旋动力学与实验可观测材料响应之间的联系。