Photo-Induced Enhancement of Critical Temperature in a Phase Competing Spin-Fermion System
Fuente:
arXiv
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| Formato: | Preprint |
| Publicado: |
2025
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| _version_ | 1866908555825643520 |
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| author | Bakshi, Sankha Subhra |
| author_facet | Bakshi, Sankha Subhra |
| contents | Ultrafast optical excitation is known to destabilize long-range order in correlated systems, yet experiments have also reported the emergence of metastable phases, in some cases with enhanced critical temperatures. The microscopic origin of such light-induced stabilization remains unresolved. Here we investigate this problem within a minimal spin-fermion framework: a double-exchange model at half filling, augmented by ferromagnetic superexchange on a square lattice. In equilibrium, at half-filling the ordering temperature is set by the competition between kinetic-energy-driven antiferromagnetism and superexchange-induced ferromagnetism. Using quantum Landau-Lifshitz-Gilbert-Brown dynamics for localized spins combined with mean-field evolution of itinerant electrons, we demonstrate a nonthermal mechanism for stabilizing ordered phases. Photoexcitation creates a long-lived nonequilibrium carrier population that resists thermalization and reshapes the low-energy landscape, converting kinetic-energy-driven antiferromagnetism into ferromagnetism and enhancing the critical temperature. While model-specific, our results reveal a general microscopic pathway by which light can tip the balance between competing orders, suggesting routes toward optically engineered magnetism, charge-density-wave order, and superconductivity. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2509_19262 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Photo-Induced Enhancement of Critical Temperature in a Phase Competing Spin-Fermion System Bakshi, Sankha Subhra Strongly Correlated Electrons Ultrafast optical excitation is known to destabilize long-range order in correlated systems, yet experiments have also reported the emergence of metastable phases, in some cases with enhanced critical temperatures. The microscopic origin of such light-induced stabilization remains unresolved. Here we investigate this problem within a minimal spin-fermion framework: a double-exchange model at half filling, augmented by ferromagnetic superexchange on a square lattice. In equilibrium, at half-filling the ordering temperature is set by the competition between kinetic-energy-driven antiferromagnetism and superexchange-induced ferromagnetism. Using quantum Landau-Lifshitz-Gilbert-Brown dynamics for localized spins combined with mean-field evolution of itinerant electrons, we demonstrate a nonthermal mechanism for stabilizing ordered phases. Photoexcitation creates a long-lived nonequilibrium carrier population that resists thermalization and reshapes the low-energy landscape, converting kinetic-energy-driven antiferromagnetism into ferromagnetism and enhancing the critical temperature. While model-specific, our results reveal a general microscopic pathway by which light can tip the balance between competing orders, suggesting routes toward optically engineered magnetism, charge-density-wave order, and superconductivity. |
| title | Photo-Induced Enhancement of Critical Temperature in a Phase Competing Spin-Fermion System |
| topic | Strongly Correlated Electrons |
| url | https://arxiv.org/abs/2509.19262 |