Strong Intra- and Interchain Orbital Coupling Leads to Multiband and High Thermoelectric Performance in Na$_2$Au$X$ ($X$ = P, As, Sb, and Bi)
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2025
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| _version_ | 1866918175103254528 |
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| author | Xia, Zhonghao Yang, Zhilong Yang, Yali Ren, Kaile He, Jiangang |
| author_facet | Xia, Zhonghao Yang, Zhilong Yang, Yali Ren, Kaile He, Jiangang |
| contents | The intrinsic coupling among electrical conductivity ($σ$), Seebeck coefficient ($S$), and lattice thermal conductivity ($κ_{\mathrm{L}}$) imposes a fundamental limit on the dimensionless figure of merit $ZT$ in thermoelectric (TE) materials. Increasing band degeneracy can effectively balance $σ$ and $S$, enabling a high power factor (PF, $S^{2}σ$). However, compounds with intrinsically large band degeneracy are scarce. Here, we present an unconventional strategy to realize elevated band degeneracy in zigzag-chain Na$_2$Au$X$ ($X$ = P, As, Sb, Bi) compounds by harnessing strong intra- and interchain orbital coupling. Pronounced hybridization between Au-$d_{z^{2}}$ and $X$-$p_{z}$ orbitals along the Au--$X$ zigzag chains, together with unexpectedly strong interchain $X$-$p_{x}/p_{y}$ coupling, produces a highly dispersive, multivalley valence band structure that supports an exceptional PF. Concurrently, the intrinsically weak interchain interactions arising from the quasi-one-dimensional framework, together with the weakened Au--$X$ and Au--Au bonds within the chains due to filling of $p$-$d^{*}$ antibonding states, result in an ultralow $κ_{\mathrm{L}}$. First-principles calculations combined with Boltzmann transport theory predict that $p$-type Na$_2$AuBi achieves a PF of $63.9\,μ\mathrm{W}\,\mathrm{cm}^{-1}\,\mathrm{K}^{-2}$, an ultralow $κ_{\mathrm{L}}$ of $0.49\,\mathrm{W}\,\mathrm{m}^{-1}\,\mathrm{K}^{-1}$, and a maximum $ZT$ of $4.7$ along the zigzag-chain direction at $800\,\mathrm{K}$. This work establishes a new design paradigm for high-efficiency TE materials by exploiting substantial orbital overlap in structurally weakly bonded, quasi-one-dimensional systems, opening promising avenues for the discovery and engineering of next-generation high-performance TE materials. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2510_23983 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Strong Intra- and Interchain Orbital Coupling Leads to Multiband and High Thermoelectric Performance in Na$_2$Au$X$ ($X$ = P, As, Sb, and Bi) Xia, Zhonghao Yang, Zhilong Yang, Yali Ren, Kaile He, Jiangang Materials Science The intrinsic coupling among electrical conductivity ($σ$), Seebeck coefficient ($S$), and lattice thermal conductivity ($κ_{\mathrm{L}}$) imposes a fundamental limit on the dimensionless figure of merit $ZT$ in thermoelectric (TE) materials. Increasing band degeneracy can effectively balance $σ$ and $S$, enabling a high power factor (PF, $S^{2}σ$). However, compounds with intrinsically large band degeneracy are scarce. Here, we present an unconventional strategy to realize elevated band degeneracy in zigzag-chain Na$_2$Au$X$ ($X$ = P, As, Sb, Bi) compounds by harnessing strong intra- and interchain orbital coupling. Pronounced hybridization between Au-$d_{z^{2}}$ and $X$-$p_{z}$ orbitals along the Au--$X$ zigzag chains, together with unexpectedly strong interchain $X$-$p_{x}/p_{y}$ coupling, produces a highly dispersive, multivalley valence band structure that supports an exceptional PF. Concurrently, the intrinsically weak interchain interactions arising from the quasi-one-dimensional framework, together with the weakened Au--$X$ and Au--Au bonds within the chains due to filling of $p$-$d^{*}$ antibonding states, result in an ultralow $κ_{\mathrm{L}}$. First-principles calculations combined with Boltzmann transport theory predict that $p$-type Na$_2$AuBi achieves a PF of $63.9\,μ\mathrm{W}\,\mathrm{cm}^{-1}\,\mathrm{K}^{-2}$, an ultralow $κ_{\mathrm{L}}$ of $0.49\,\mathrm{W}\,\mathrm{m}^{-1}\,\mathrm{K}^{-1}$, and a maximum $ZT$ of $4.7$ along the zigzag-chain direction at $800\,\mathrm{K}$. This work establishes a new design paradigm for high-efficiency TE materials by exploiting substantial orbital overlap in structurally weakly bonded, quasi-one-dimensional systems, opening promising avenues for the discovery and engineering of next-generation high-performance TE materials. |
| title | Strong Intra- and Interchain Orbital Coupling Leads to Multiband and High Thermoelectric Performance in Na$_2$Au$X$ ($X$ = P, As, Sb, and Bi) |
| topic | Materials Science |
| url | https://arxiv.org/abs/2510.23983 |