Lattice Dynamics involving Nuclear Tunneling in 2D Materials

Objective

Lattice dynamics plays a fundamental role in determining electrical and thermal conductivities, which are key physical properties closely associated with energy utilization mechanisms. Nuclear tunneling motion in crystals results in lattice dynamics that differ from conventional phonons, potentially giving rise to novel transport properties. In this fellowship, I will unravel the quantum many-body nature of lattice degrees of freedom and develop computational methods to describe lattice dynamics involving nuclear tunneling, with a focus on 2D materials. Among these novel properties, low thermal conductivity coupled with high electrical conductivity is the defining feature of high-performance thermoelectric materials. These materials enable direct conversion of waste heat into electricity and hold revolutionary potential for applications in energy harvesting, electronics, and aerospace. The Holy Grail in thermoelectrics is a single crystal that combines high electrical conductivity with ultra-low thermal conductivity. Although many crystals with low thermal conductivity have been discovered, a complete microscopic understanding of the underlying mechanisms remains elusive. Spectroscopic and transport measurements have provided growing evidence of nuclear tunneling in crystals, suggesting a departure from phonon-based lattice dynamics. However, the theoretical framework describing these dynamics remains underdeveloped. In this fellowship, I will develop a computational method for lattice dynamics involving nuclear quantum tunneling to unravel its quantum many-body nature, explore the novel quantum disordered phase in ice monolayer, and investigate the origin of anomalous thermal conductivity and the influence of quantum tunneling on thermal and electrical conductivities in 2D systems. This project will uncover the fundamental physics and open new pathways for designing next-generation high-performance materials.