--- _id: '8587' abstract: - lang: eng text: Inspired by the possibility to experimentally manipulate and enhance chemical reactivity in helium nanodroplets, we investigate the effective interaction and the resulting correlations between two diatomic molecules immersed in a bath of bosons. By analogy with the bipolaron, we introduce the biangulon quasiparticle describing two rotating molecules that align with respect to each other due to the effective attractive interaction mediated by the excitations of the bath. We study this system in different parameter regimes and apply several theoretical approaches to describe its properties. Using a Born–Oppenheimer approximation, we investigate the dependence of the effective intermolecular interaction on the rotational state of the two molecules. In the strong-coupling regime, a product-state ansatz shows that the molecules tend to have a strong alignment in the ground state. To investigate the system in the weak-coupling regime, we apply a one-phonon excitation variational ansatz, which allows us to access the energy spectrum. In comparison to the angulon quasiparticle, the biangulon shows shifted angulon instabilities and an additional spectral instability, where resonant angular momentum transfer between the molecules and the bath takes place. These features are proposed as an experimentally observable signature for the formation of the biangulon quasiparticle. Finally, by using products of single angulon and bare impurity wave functions as basis states, we introduce a diagonalization scheme that allows us to describe the transition from two separated angulons to a biangulon as a function of the distance between the two molecules. acknowledgement: We are grateful to Areg Ghazaryan for valuable discussions. M.L. acknowledges support from the Austrian Science Fund (FWF) under Project No. P29902-N27 and from the European Research Council (ERC) Starting Grant No. 801770 (ANGULON). G.B. acknowledges support from the Austrian Science Fund (FWF) under Project No. M2461-N27. A.D. acknowledges funding from the European Union’s Horizon 2020 research and innovation programme under the European Research Council (ERC) Grant Agreement No. 694227 and under the Marie Sklodowska-Curie Grant Agreement No. 836146. R.S. was supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy – EXC-2111 – 390814868. article_number: '164302' article_processing_charge: No article_type: original author: - first_name: Xiang full_name: Li, Xiang id: 4B7E523C-F248-11E8-B48F-1D18A9856A87 last_name: Li - first_name: Enderalp full_name: Yakaboylu, Enderalp id: 38CB71F6-F248-11E8-B48F-1D18A9856A87 last_name: Yakaboylu orcid: 0000-0001-5973-0874 - first_name: Giacomo full_name: Bighin, Giacomo id: 4CA96FD4-F248-11E8-B48F-1D18A9856A87 last_name: Bighin orcid: 0000-0001-8823-9777 - first_name: Richard full_name: Schmidt, Richard last_name: Schmidt - first_name: Mikhail full_name: Lemeshko, Mikhail id: 37CB05FA-F248-11E8-B48F-1D18A9856A87 last_name: Lemeshko orcid: 0000-0002-6990-7802 - first_name: Andreas full_name: Deuchert, Andreas id: 4DA65CD0-F248-11E8-B48F-1D18A9856A87 last_name: Deuchert orcid: 0000-0003-3146-6746 citation: ama: Li X, Yakaboylu E, Bighin G, Schmidt R, Lemeshko M, Deuchert A. Intermolecular forces and correlations mediated by a phonon bath. The Journal of Chemical Physics. 2020;152(16). doi:10.1063/1.5144759 apa: Li, X., Yakaboylu, E., Bighin, G., Schmidt, R., Lemeshko, M., & Deuchert, A. (2020). Intermolecular forces and correlations mediated by a phonon bath. The Journal of Chemical Physics. AIP Publishing. https://doi.org/10.1063/1.5144759 chicago: Li, Xiang, Enderalp Yakaboylu, Giacomo Bighin, Richard Schmidt, Mikhail Lemeshko, and Andreas Deuchert. “Intermolecular Forces and Correlations Mediated by a Phonon Bath.” The Journal of Chemical Physics. AIP Publishing, 2020. https://doi.org/10.1063/1.5144759. ieee: X. Li, E. Yakaboylu, G. Bighin, R. Schmidt, M. Lemeshko, and A. Deuchert, “Intermolecular forces and correlations mediated by a phonon bath,” The Journal of Chemical Physics, vol. 152, no. 16. AIP Publishing, 2020. ista: Li X, Yakaboylu E, Bighin G, Schmidt R, Lemeshko M, Deuchert A. 2020. Intermolecular forces and correlations mediated by a phonon bath. The Journal of Chemical Physics. 152(16), 164302. mla: Li, Xiang, et al. “Intermolecular Forces and Correlations Mediated by a Phonon Bath.” The Journal of Chemical Physics, vol. 152, no. 16, 164302, AIP Publishing, 2020, doi:10.1063/1.5144759. short: X. Li, E. Yakaboylu, G. Bighin, R. Schmidt, M. Lemeshko, A. Deuchert, The Journal of Chemical Physics 152 (2020). date_created: 2020-09-30T10:33:17Z date_published: 2020-04-27T00:00:00Z date_updated: 2023-09-07T13:16:42Z day: '27' department: - _id: MiLe - _id: RoSe doi: 10.1063/1.5144759 ec_funded: 1 external_id: arxiv: - '1912.02658' isi: - '000530448300001' intvolume: ' 152' isi: 1 issue: '16' keyword: - Physical and Theoretical Chemistry - General Physics and Astronomy language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1912.02658 month: '04' oa: 1 oa_version: Preprint project: - _id: 26031614-B435-11E9-9278-68D0E5697425 call_identifier: FWF grant_number: P29902 name: Quantum rotations in the presence of a many-body environment - _id: 2688CF98-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '801770' name: 'Angulon: physics and applications of a new quasiparticle' - _id: 26986C82-B435-11E9-9278-68D0E5697425 call_identifier: FWF grant_number: M02641 name: A path-integral approach to composite impurities - _id: 25C6DC12-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '694227' name: Analysis of quantum many-body systems publication: The Journal of Chemical Physics publication_identifier: eissn: - 1089-7690 issn: - 0021-9606 publication_status: published publisher: AIP Publishing quality_controlled: '1' related_material: record: - id: '8958' relation: dissertation_contains status: public status: public title: Intermolecular forces and correlations mediated by a phonon bath type: journal_article user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1 volume: 152 year: '2020' ... --- _id: '8958' abstract: - lang: eng text: "The oft-quoted dictum by Arthur Schawlow: ``A diatomic molecule has one atom too many'' has been disavowed. Inspired by the possibility to experimentally manipulate and enhance chemical reactivity in helium nanodroplets, we investigate the rotation of coupled cold molecules in the presence of a many-body environment.\r\nIn this thesis, we introduce new variational approaches to quantum impurities and apply them to the Fröhlich polaron - a quasiparticle formed out of an electron (or other point-like impurity) in a polar medium, and to the angulon - a quasiparticle formed out of a rotating molecule in a bosonic bath.\r\nWith this theoretical toolbox, we reveal the self-localization transition for the angulon quasiparticle. We show that, unlike for polarons, self-localization of angulons occurs at finite impurity-bath coupling already at the mean-field level. The transition is accompanied by the spherical-symmetry breaking of the angulon ground state and a discontinuity in the first derivative of the ground-state energy. Moreover, the type of symmetry breaking is dictated by the symmetry of the microscopic impurity-bath interaction, which leads to a number of distinct self-localized states. \r\nFor the system containing multiple impurities, by analogy with the bipolaron, we introduce the biangulon quasiparticle describing two rotating molecules that align with respect to each other due to the effective attractive interaction mediated by the excitations of the bath. We study this system from the strong-coupling regime to the weak molecule-bath interaction regime. We show that the molecules tend to have a strong alignment in the ground state, the biangulon shows shifted angulon instabilities and an additional spectral instability, where resonant angular momentum transfer between the molecules and the bath takes place. Finally, we introduce a diagonalization scheme that allows us to describe the transition from two separated angulons to a biangulon as a function of the distance between the two molecules." alternative_title: - ISTA Thesis article_processing_charge: No author: - first_name: Xiang full_name: Li, Xiang id: 4B7E523C-F248-11E8-B48F-1D18A9856A87 last_name: Li citation: ama: Li X. Rotation of coupled cold molecules in the presence of a many-body environment. 2020. doi:10.15479/AT:ISTA:8958 apa: Li, X. (2020). Rotation of coupled cold molecules in the presence of a many-body environment. Institute of Science and Technology Austria. https://doi.org/10.15479/AT:ISTA:8958 chicago: Li, Xiang. “Rotation of Coupled Cold Molecules in the Presence of a Many-Body Environment.” Institute of Science and Technology Austria, 2020. https://doi.org/10.15479/AT:ISTA:8958. ieee: X. Li, “Rotation of coupled cold molecules in the presence of a many-body environment,” Institute of Science and Technology Austria, 2020. ista: Li X. 2020. Rotation of coupled cold molecules in the presence of a many-body environment. Institute of Science and Technology Austria. mla: Li, Xiang. Rotation of Coupled Cold Molecules in the Presence of a Many-Body Environment. Institute of Science and Technology Austria, 2020, doi:10.15479/AT:ISTA:8958. short: X. Li, Rotation of Coupled Cold Molecules in the Presence of a Many-Body Environment, Institute of Science and Technology Austria, 2020. date_created: 2020-12-21T09:44:30Z date_published: 2020-12-21T00:00:00Z date_updated: 2023-09-20T11:30:58Z day: '21' ddc: - '539' degree_awarded: PhD department: - _id: MiLe doi: 10.15479/AT:ISTA:8958 ec_funded: 1 file: - access_level: open_access checksum: 3994c54a1241451d561db1d4f43bad30 content_type: application/pdf creator: xli date_created: 2020-12-22T10:55:56Z date_updated: 2020-12-22T10:55:56Z file_id: '8967' file_name: THESIS_Xiang_Li.pdf file_size: 3622305 relation: main_file success: 1 - access_level: closed checksum: 0954ecfc5554c05615c14de803341f00 content_type: application/x-zip-compressed creator: xli date_created: 2020-12-22T10:56:03Z date_updated: 2020-12-30T07:18:03Z file_id: '8968' file_name: THESIS_Xiang_Li.zip file_size: 4018859 relation: source_file file_date_updated: 2020-12-30T07:18:03Z has_accepted_license: '1' language: - iso: eng month: '12' oa: 1 oa_version: Published Version page: '125' project: - _id: 26031614-B435-11E9-9278-68D0E5697425 call_identifier: FWF grant_number: P29902 name: Quantum rotations in the presence of a many-body environment - _id: 2688CF98-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '801770' name: 'Angulon: physics and applications of a new quasiparticle' publication_identifier: issn: - 2663-337X publication_status: published publisher: Institute of Science and Technology Austria related_material: record: - id: '5886' relation: part_of_dissertation status: public - id: '8587' relation: part_of_dissertation status: public - id: '1120' relation: part_of_dissertation status: public status: public supervisor: - first_name: Mikhail full_name: Lemeshko, Mikhail id: 37CB05FA-F248-11E8-B48F-1D18A9856A87 last_name: Lemeshko orcid: 0000-0002-6990-7802 title: Rotation of coupled cold molecules in the presence of a many-body environment type: dissertation user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1 year: '2020' ... --- _id: '5886' abstract: - lang: eng text: Problems involving quantum impurities, in which one or a few particles are interacting with a macroscopic environment, represent a pervasive paradigm, spanning across atomic, molecular, and condensed-matter physics. In this paper we introduce new variational approaches to quantum impurities and apply them to the Fröhlich polaron–a quasiparticle formed out of an electron (or other point-like impurity) in a polar medium, and to the angulon–a quasiparticle formed out of a rotating molecule in a bosonic bath. We benchmark these approaches against established theories, evaluating their accuracy as a function of the impurity-bath coupling. article_processing_charge: No author: - first_name: Xiang full_name: Li, Xiang id: 4B7E523C-F248-11E8-B48F-1D18A9856A87 last_name: Li - first_name: Giacomo full_name: Bighin, Giacomo id: 4CA96FD4-F248-11E8-B48F-1D18A9856A87 last_name: Bighin orcid: 0000-0001-8823-9777 - first_name: Enderalp full_name: Yakaboylu, Enderalp id: 38CB71F6-F248-11E8-B48F-1D18A9856A87 last_name: Yakaboylu orcid: 0000-0001-5973-0874 - first_name: Mikhail full_name: Lemeshko, Mikhail id: 37CB05FA-F248-11E8-B48F-1D18A9856A87 last_name: Lemeshko orcid: 0000-0002-6990-7802 citation: ama: 'Li X, Bighin G, Yakaboylu E, Lemeshko M. Variational approaches to quantum impurities: from the Fröhlich polaron to the angulon. Molecular Physics. 2019. doi:10.1080/00268976.2019.1567852' apa: 'Li, X., Bighin, G., Yakaboylu, E., & Lemeshko, M. (2019). Variational approaches to quantum impurities: from the Fröhlich polaron to the angulon. Molecular Physics. Taylor and Francis. https://doi.org/10.1080/00268976.2019.1567852' chicago: 'Li, Xiang, Giacomo Bighin, Enderalp Yakaboylu, and Mikhail Lemeshko. “Variational Approaches to Quantum Impurities: From the Fröhlich Polaron to the Angulon.” Molecular Physics. Taylor and Francis, 2019. https://doi.org/10.1080/00268976.2019.1567852.' ieee: 'X. Li, G. Bighin, E. Yakaboylu, and M. Lemeshko, “Variational approaches to quantum impurities: from the Fröhlich polaron to the angulon,” Molecular Physics. Taylor and Francis, 2019.' ista: 'Li X, Bighin G, Yakaboylu E, Lemeshko M. 2019. Variational approaches to quantum impurities: from the Fröhlich polaron to the angulon. Molecular Physics.' mla: 'Li, Xiang, et al. “Variational Approaches to Quantum Impurities: From the Fröhlich Polaron to the Angulon.” Molecular Physics, Taylor and Francis, 2019, doi:10.1080/00268976.2019.1567852.' short: X. Li, G. Bighin, E. Yakaboylu, M. Lemeshko, Molecular Physics (2019). date_created: 2019-01-27T22:59:10Z date_published: 2019-01-18T00:00:00Z date_updated: 2023-09-07T13:16:42Z day: '18' ddc: - '530' department: - _id: MiLe doi: 10.1080/00268976.2019.1567852 ec_funded: 1 external_id: isi: - '000474641400008' file: - access_level: open_access checksum: 178964744b636a6f036372f4f090a657 content_type: application/pdf creator: dernst date_created: 2019-01-29T08:32:57Z date_updated: 2020-07-14T12:47:13Z file_id: '5896' file_name: 2019_MolecularPhysics_Li.pdf file_size: 1309966 relation: main_file file_date_updated: 2020-07-14T12:47:13Z has_accepted_license: '1' isi: 1 language: - iso: eng license: https://creativecommons.org/licenses/by/4.0/ month: '01' oa: 1 oa_version: Published Version project: - _id: 26031614-B435-11E9-9278-68D0E5697425 call_identifier: FWF grant_number: P29902 name: Quantum rotations in the presence of a many-body environment - _id: 25681D80-B435-11E9-9278-68D0E5697425 call_identifier: FP7 grant_number: '291734' name: International IST Postdoc Fellowship Programme publication: Molecular Physics publication_identifier: issn: - '00268976' publication_status: published publisher: Taylor and Francis quality_controlled: '1' related_material: record: - id: '8958' relation: dissertation_contains status: public scopus_import: '1' status: public title: 'Variational approaches to quantum impurities: from the Fröhlich polaron to the angulon' tmp: image: /images/cc_by.png legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0) short: CC BY (4.0) type: journal_article user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8 year: '2019' ... --- _id: '1120' abstract: - lang: eng text: 'The existence of a self-localization transition in the polaron problem has been under an active debate ever since Landau suggested it 83 years ago. Here we reveal the self-localization transition for the rotational analogue of the polaron -- the angulon quasiparticle. We show that, unlike for the polarons, self-localization of angulons occurs at finite impurity-bath coupling already at the mean-field level. The transition is accompanied by the spherical-symmetry breaking of the angulon ground state and a discontinuity in the first derivative of the ground-state energy. Moreover, the type of the symmetry breaking is dictated by the symmetry of the microscopic impurity-bath interaction, which leads to a number of distinct self-localized states. The predicted effects can potentially be addressed in experiments on cold molecules trapped in superfluid helium droplets and ultracold quantum gases, as well as on electronic excitations in solids and Bose-Einstein condensates. ' article_number: '033608' article_processing_charge: No author: - first_name: Xiang full_name: Li, Xiang id: 4B7E523C-F248-11E8-B48F-1D18A9856A87 last_name: Li - first_name: Robert full_name: Seiringer, Robert id: 4AFD0470-F248-11E8-B48F-1D18A9856A87 last_name: Seiringer orcid: 0000-0002-6781-0521 - first_name: Mikhail full_name: Lemeshko, Mikhail id: 37CB05FA-F248-11E8-B48F-1D18A9856A87 last_name: Lemeshko orcid: 0000-0002-6990-7802 citation: ama: Li X, Seiringer R, Lemeshko M. Angular self-localization of impurities rotating in a bosonic bath. Physical Review A. 2017;95(3). doi:10.1103/PhysRevA.95.033608 apa: Li, X., Seiringer, R., & Lemeshko, M. (2017). Angular self-localization of impurities rotating in a bosonic bath. Physical Review A. American Physical Society. https://doi.org/10.1103/PhysRevA.95.033608 chicago: Li, Xiang, Robert Seiringer, and Mikhail Lemeshko. “Angular Self-Localization of Impurities Rotating in a Bosonic Bath.” Physical Review A. American Physical Society, 2017. https://doi.org/10.1103/PhysRevA.95.033608. ieee: X. Li, R. Seiringer, and M. Lemeshko, “Angular self-localization of impurities rotating in a bosonic bath,” Physical Review A, vol. 95, no. 3. American Physical Society, 2017. ista: Li X, Seiringer R, Lemeshko M. 2017. Angular self-localization of impurities rotating in a bosonic bath. Physical Review A. 95(3), 033608. mla: Li, Xiang, et al. “Angular Self-Localization of Impurities Rotating in a Bosonic Bath.” Physical Review A, vol. 95, no. 3, 033608, American Physical Society, 2017, doi:10.1103/PhysRevA.95.033608. short: X. Li, R. Seiringer, M. Lemeshko, Physical Review A 95 (2017). date_created: 2018-12-11T11:50:15Z date_published: 2017-03-06T00:00:00Z date_updated: 2023-09-20T11:30:58Z day: '06' department: - _id: MiLe - _id: RoSe doi: 10.1103/PhysRevA.95.033608 ec_funded: 1 external_id: isi: - '000395981900009' intvolume: ' 95' isi: 1 issue: '3' language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1610.04908 month: '03' oa: 1 oa_version: Published Version project: - _id: 25C6DC12-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '694227' name: Analysis of quantum many-body systems - _id: 25C878CE-B435-11E9-9278-68D0E5697425 call_identifier: FWF grant_number: P27533_N27 name: Structure of the Excitation Spectrum for Many-Body Quantum Systems - _id: 26031614-B435-11E9-9278-68D0E5697425 call_identifier: FWF grant_number: P29902 name: Quantum rotations in the presence of a many-body environment publication: Physical Review A publication_identifier: issn: - '24699926' publication_status: published publisher: American Physical Society publist_id: '6242' quality_controlled: '1' related_material: record: - id: '8958' relation: dissertation_contains status: public scopus_import: '1' status: public title: Angular self-localization of impurities rotating in a bosonic bath type: journal_article user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1 volume: 95 year: '2017' ... --- _id: '3555' abstract: - lang: eng text: A sliver is a tetrahedron whose four vertices lie close to a plane and whose perpendicular projection to that plane is a convex quadrilateral with no short edge. Slivers are both undesirable and ubiquitous in 3-dimensional Delaunay triangulations. Even when the point-set is well-spaced, slivers may result. This paper shows that such a point set permits a small perturbation whose Delaunay triangulation contains no slivers. It also gives deterministic algorithms that compute the perturbation of n points in time O(n log n) with one processor and in time O(log n) with O(n) processors. article_processing_charge: No author: - first_name: Herbert full_name: Edelsbrunner, Herbert id: 3FB178DA-F248-11E8-B48F-1D18A9856A87 last_name: Edelsbrunner orcid: 0000-0002-9823-6833 - first_name: Xiang full_name: Li, Xiang id: 4B7E523C-F248-11E8-B48F-1D18A9856A87 last_name: Li - first_name: Gary full_name: Miller, Gary last_name: Miller - first_name: Andreas full_name: Stathopoulos, Andreas last_name: Stathopoulos - first_name: Dafna full_name: Talmor, Dafna last_name: Talmor - first_name: Shang full_name: Teng, Shang last_name: Teng - first_name: Alper full_name: Üngör, Alper last_name: Üngör - first_name: Noel full_name: Walkington, Noel last_name: Walkington citation: ama: 'Edelsbrunner H, Li X, Miller G, et al. Smoothing and cleaning up slivers. In: Proceedings of the 32nd Annual ACM Symposium on Theory of Computing. ACM; 2000:273-277. doi:10.1145/335305.335338' apa: 'Edelsbrunner, H., Li, X., Miller, G., Stathopoulos, A., Talmor, D., Teng, S., … Walkington, N. (2000). Smoothing and cleaning up slivers. In Proceedings of the 32nd annual ACM symposium on Theory of computing (pp. 273–277). Portland, OR, USA: ACM. https://doi.org/10.1145/335305.335338' chicago: Edelsbrunner, Herbert, Xiang Li, Gary Miller, Andreas Stathopoulos, Dafna Talmor, Shang Teng, Alper Üngör, and Noel Walkington. “Smoothing and Cleaning up Slivers.” In Proceedings of the 32nd Annual ACM Symposium on Theory of Computing, 273–77. ACM, 2000. https://doi.org/10.1145/335305.335338. ieee: H. Edelsbrunner et al., “Smoothing and cleaning up slivers,” in Proceedings of the 32nd annual ACM symposium on Theory of computing, Portland, OR, USA, 2000, pp. 273–277. ista: 'Edelsbrunner H, Li X, Miller G, Stathopoulos A, Talmor D, Teng S, Üngör A, Walkington N. 2000. Smoothing and cleaning up slivers. Proceedings of the 32nd annual ACM symposium on Theory of computing. STOC: Symposium on the Theory of Computing, 273–277.' mla: Edelsbrunner, Herbert, et al. “Smoothing and Cleaning up Slivers.” Proceedings of the 32nd Annual ACM Symposium on Theory of Computing, ACM, 2000, pp. 273–77, doi:10.1145/335305.335338. short: H. Edelsbrunner, X. Li, G. Miller, A. Stathopoulos, D. Talmor, S. Teng, A. Üngör, N. Walkington, in:, Proceedings of the 32nd Annual ACM Symposium on Theory of Computing, ACM, 2000, pp. 273–277. conference: end_date: 2000-05-23 location: Portland, OR, USA name: 'STOC: Symposium on the Theory of Computing' start_date: 2000-05-21 date_created: 2018-12-11T12:03:56Z date_published: 2000-06-01T00:00:00Z date_updated: 2023-05-02T14:07:00Z day: '01' doi: 10.1145/335305.335338 extern: '1' language: - iso: eng month: '06' oa_version: None page: 273 - 277 publication: Proceedings of the 32nd annual ACM symposium on Theory of computing publication_identifier: isbn: - '9781581131840' publication_status: published publisher: ACM publist_id: '2830' quality_controlled: '1' scopus_import: '1' status: public title: Smoothing and cleaning up slivers type: conference user_id: ea97e931-d5af-11eb-85d4-e6957dddbf17 year: '2000' ...