The ultra-low lattice thermal conductivity dominated by the quartic anharmonicity in Bi-based binary compounds A₃Bi (A = K, Rb)

¹ Department of Physics, Yantai University - Yantai 264005, PRC
² Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences Beijing, 100190, PRC
³ Collaborative Innovation Center of Quantum Matter - Beijing 100084, PRC

^(a) y.zhao@ytu.edu.cn
^(b) smeng@iphy.ac.cn
^(c) zhdai@ytu.edu.cn (corresponding author)

Received: 15 December 2021
Accepted: 24 May 2022

Abstract

In this article, by using self-consistent phonon (SCP) theory, compressed sensing (CS) technology and Boltzmann transport equation (BTE), we studied the role of quartic anharmonicity in the lattice dynamics and thermal transport characteristics of Bi-based binary compounds A₃Bi (A = K, Rb), with a particular focus on unraveling the impacts of quartic anharmonicity on lattice thermal conductivity . By analyzing the phonon dispersion curve and the phonon density of states, we found that the strong quartic anharmonicity, which is mainly caused by the alkali metal atoms A1 in A₃Bi (A = K, Rb), hardens the vibration frequency of the low-lying phonon branch and ensures the lattice dynamic stability. Through the relaxation time approximation of the Boltzmann transport equation, the calculated considering the three-phonon (3ph) and four-phonon (4ph) scattering process shows an ultra-low value. In addition, we also conducted a detailed analysis of the normalized lattice thermal conductivity, phonon group velocity, phonon scattering rate, and scattering phase space, revealing that the extremely low in A₃Bi is mainly due to its relatively strong 4ph scattering process. Our research proves the existence of strong quartic anharmonicity in A₃Bi, and we have studied in detail the influence of 3ph and 4ph scattering processes on the thermal transport properties of A₃Bi, which has never been reported before.