%0 Journal Article %1 PhysRevB.105.094419 %A Miao, Yuanyuan %A Chen, Liyuan %A Zhang, Guangping %A Wang, Chuankui %A Ren, Junfeng %A Timm, Carsten %A Hu, Guichao %D 2022 %I American Physical Society %J Phys. Rev. B %K b %N 9 %P 094419 %R 10.1103/PhysRevB.105.094419 %T Mechanism of length-induced magnetism in polyacene molecules %U https://link.aps.org/doi/10.1103/PhysRevB.105.094419 %V 105 %X Within the celebrated Su-Schrieffer-Heeger model including electron-lattice and electron-electron interactions, the electronic ground state of polyacene (n-acene) is studied as a function of molecular length n. The results demonstrate that the ground state exhibits a phase transition from a nonmagnetic state to an antiferromagnetic state at a critical length of n=7. The magnetism is explained by calculating the lattice distortion and the related average hopping rate of the π electrons. It is revealed that in polyacenes, there exist two competing mechanisms that minimize the molecular energy, namely the lattice dimerization and the formation of an antiferromagnetic spin density. Since the dimerization is restricted to the regions near the ends of the molecules the former mechanism is dominant for short molecules, which therefore assume a nonmagnetic state. When the length is increased beyond the critical value, the lattice dimerization in the middle of the molecule is reduced and a rapid drop of the average hopping rate occurs. This makes the second mechanism dominant and the associated antiferromagnetic state is stabilized. The effect of different interaction strengths and values of hopping integrals on the critical length is discussed. The results are confirmed by first-principles calculations. Suggestions for the design of organic antiferromagnets with a similar ladder structure are also given.

@article{PhysRevB.105.094419, abstract = {Within the celebrated Su-Schrieffer-Heeger model including electron-lattice and electron-electron interactions, the electronic ground state of polyacene (n-acene) is studied as a function of molecular length n. The results demonstrate that the ground state exhibits a phase transition from a nonmagnetic state to an antiferromagnetic state at a critical length of n=7. The magnetism is explained by calculating the lattice distortion and the related average hopping rate of the π electrons. It is revealed that in polyacenes, there exist two competing mechanisms that minimize the molecular energy, namely the lattice dimerization and the formation of an antiferromagnetic spin density. Since the dimerization is restricted to the regions near the ends of the molecules the former mechanism is dominant for short molecules, which therefore assume a nonmagnetic state. When the length is increased beyond the critical value, the lattice dimerization in the middle of the molecule is reduced and a rapid drop of the average hopping rate occurs. This makes the second mechanism dominant and the associated antiferromagnetic state is stabilized. The effect of different interaction strengths and values of hopping integrals on the critical length is discussed. The results are confirmed by first-principles calculations. Suggestions for the design of organic antiferromagnets with a similar ladder structure are also given.}, added-at = {2022-05-31T16:30:24.000+0200}, author = {Miao, Yuanyuan and Chen, Liyuan and Zhang, Guangping and Wang, Chuankui and Ren, Junfeng and Timm, Carsten and Hu, Guichao}, biburl = {https://www.bibsonomy.org/bibtex/2f19df917ab85be2574df139949a0fd10/ctqmat}, day = 14, description = {Phys. Rev. B 105, 094419 (2022) - Mechanism of length-induced magnetism in polyacene molecules}, doi = {10.1103/PhysRevB.105.094419}, interhash = {77357b4d42beda588bde6f0fe780fb5e}, intrahash = {f19df917ab85be2574df139949a0fd10}, journal = {Phys. Rev. B}, keywords = {b}, month = {03}, number = 9, numpages = {10}, pages = 094419, publisher = {American Physical Society}, timestamp = {2023-01-16T14:49:29.000+0100}, title = {Mechanism of length-induced magnetism in polyacene molecules}, url = {https://link.aps.org/doi/10.1103/PhysRevB.105.094419}, volume = 105, year = 2022 }