Strain-Induced Half-Metallicity and Giant Wiedemann-Franz Violation in Monolayer NiI$_2$
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arXiv
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| Natura: | Preprint |
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2025
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| _version_ | 1866909958999638016 |
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| author | González, J. W. Rosales, L. |
| author_facet | González, J. W. Rosales, L. |
| contents | Reversible control of spin-dependent thermoelectricity via mechanical strain provides a platform for next-generation energy harvesting and thermal logic circuits. Using first-principles and Boltzmann transport calculations, we demonstrate that monolayer NiI$_2$ undergoes a strain-driven semiconductor-to-half-metal transition, enabled by the selective closure of its spin-down band gap while preserving a robust ferromagnetic ground state. Remarkably, this transition is accompanied by a giant, non-monotonic violation of the Wiedemann-Franz law, with the Lorenz number enhanced up to $7.17\,L_0$. This anomaly arises from a strain-sensitive hybridization between Ni-$d$ and I-$p$ orbitals, leading to spin-polarized transport channels and decoupling of heat and charge currents. These properties make NiI$_2$ a promising candidate for mechanically gated spin-caloritronic devices and thermal logic elements, where reversible control of heat and spin flow is essential. Our findings position NiI$_2$ as a model system for exploring non-Fermi-liquid transport and for realizing strain-tunable, energy-efficient functionalities in low-dimensional platforms. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2506_06855 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Strain-Induced Half-Metallicity and Giant Wiedemann-Franz Violation in Monolayer NiI$_2$ González, J. W. Rosales, L. Mesoscale and Nanoscale Physics Materials Science Reversible control of spin-dependent thermoelectricity via mechanical strain provides a platform for next-generation energy harvesting and thermal logic circuits. Using first-principles and Boltzmann transport calculations, we demonstrate that monolayer NiI$_2$ undergoes a strain-driven semiconductor-to-half-metal transition, enabled by the selective closure of its spin-down band gap while preserving a robust ferromagnetic ground state. Remarkably, this transition is accompanied by a giant, non-monotonic violation of the Wiedemann-Franz law, with the Lorenz number enhanced up to $7.17\,L_0$. This anomaly arises from a strain-sensitive hybridization between Ni-$d$ and I-$p$ orbitals, leading to spin-polarized transport channels and decoupling of heat and charge currents. These properties make NiI$_2$ a promising candidate for mechanically gated spin-caloritronic devices and thermal logic elements, where reversible control of heat and spin flow is essential. Our findings position NiI$_2$ as a model system for exploring non-Fermi-liquid transport and for realizing strain-tunable, energy-efficient functionalities in low-dimensional platforms. |
| title | Strain-Induced Half-Metallicity and Giant Wiedemann-Franz Violation in Monolayer NiI$_2$ |
| topic | Mesoscale and Nanoscale Physics Materials Science |
| url | https://arxiv.org/abs/2506.06855 |