Identifying Key Descriptors in ZrSe2/HfSe2-based Heterostructure and Superlattice for Enhancing Thermoelectric Performance

Abstract

Engineering heterostructure (HS) and superlattice monolayer (SLM) with trigonal symmetry not only provide versatile platforms for exploring material chemistry, it also furnish avenues to thoroughly examine carrier transport mechanisms in achieving high-performance thermoelectric materials. In this context, our study encompasses a comprehensive understanding on structural stability and, especially, the role of interface coupling resulting in thermal transport and thermoelectric properties of ZrSe2/HfSe2 in HS and SLM form. Here, we apply different approaches such as Debye-Callaway, Slack, relaxation time approximation (RTA), iterative methodology to obtain phonon transport coefficients and critically analyse the suitability of these approaches in computing lattice thermal conductivity for HS and SLM. The thermal properties study revealing the appearance of soft optical mode at zone-centre in HS, plays a driving role in controlling the phonon transport by enhancing the three phonon scattering rates especially prominent AAO and AOO scattering processes, while the scattering mechanism is completely non-identical in SLM. Other side, the SLM structure depicts staircase-like two-dimensional (2D) density of states, particularly beneficial to enhance electronic transport and exhibits competitive thermoelectric performance. We also carefully recognise useful descriptors such as phonon group velocity, scattering rates, Grüneisen parameters, phase-space volume, that identify HS and SLM. Overall, our work demonstrates new insights into the materials chemistry perspectives involved in phonon and electronic transport phenomenon for HS & SLM and provides also a broad aspect on interface coupling in assessing carrier transport properties in the field of thermoelectricity.