--- _id: '10620' abstract: - lang: eng text: Partially filled Landau levels host competing electronic orders. For example, electron solids may prevail close to integer filling of the Landau levels before giving way to fractional quantum Hall liquids at higher carrier density1,2. Here, we report the observation of an electron solid with non-collinear spin texture in monolayer graphene, consistent with solidification of skyrmions3—topological spin textures characterized by quantized electrical charge4,5. We probe the spin texture of the solids using a modified Corbino geometry that allows ferromagnetic magnons to be launched and detected6,7. We find that magnon transport is highly efficient when one Landau level is filled (ν=1), consistent with quantum Hall ferromagnetic spin polarization. However, even minimal doping immediately quenches the magnon signal while leaving the vanishing low-temperature charge conductivity unchanged. Our results can be understood by the formation of a solid of charged skyrmions near ν=1, whose non-collinear spin texture leads to rapid magnon decay. Data near fractional fillings show evidence of several fractional skyrmion solids, suggesting that graphene hosts a highly tunable landscape of coupled spin and charge orders. acknowledgement: We acknowledge discussions with B. Halperin, C. Huang, A. Macdonald and M. Zalatel. Experimental work at UCSB was supported by the Army Research Office under awards nos. MURI W911NF-16-1-0361 and W911NF-16-1-0482. K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by MEXT (Japan) and CREST (JPMJCR15F3), JST. A.F.Y. acknowledges the support of the David and Lucile Packard Foundation and and Alfred. P. Sloan Foundation. article_processing_charge: No article_type: original author: - first_name: H. full_name: Zhou, H. last_name: Zhou - first_name: Hryhoriy full_name: Polshyn, Hryhoriy id: edfc7cb1-526e-11ec-b05a-e6ecc27e4e48 last_name: Polshyn orcid: 0000-0001-8223-8896 - first_name: T. full_name: Taniguchi, T. last_name: Taniguchi - first_name: K. full_name: Watanabe, K. last_name: Watanabe - first_name: A. F. full_name: Young, A. F. last_name: Young citation: ama: Zhou H, Polshyn H, Taniguchi T, Watanabe K, Young AF. Solids of quantum Hall skyrmions in graphene. Nature Physics. 2019;16(2):154-158. doi:10.1038/s41567-019-0729-8 apa: Zhou, H., Polshyn, H., Taniguchi, T., Watanabe, K., & Young, A. F. (2019). Solids of quantum Hall skyrmions in graphene. Nature Physics. Springer Nature. https://doi.org/10.1038/s41567-019-0729-8 chicago: Zhou, H., Hryhoriy Polshyn, T. Taniguchi, K. Watanabe, and A. F. Young. “Solids of Quantum Hall Skyrmions in Graphene.” Nature Physics. Springer Nature, 2019. https://doi.org/10.1038/s41567-019-0729-8. ieee: H. Zhou, H. Polshyn, T. Taniguchi, K. Watanabe, and A. F. Young, “Solids of quantum Hall skyrmions in graphene,” Nature Physics, vol. 16, no. 2. Springer Nature, pp. 154–158, 2019. ista: Zhou H, Polshyn H, Taniguchi T, Watanabe K, Young AF. 2019. Solids of quantum Hall skyrmions in graphene. Nature Physics. 16(2), 154–158. mla: Zhou, H., et al. “Solids of Quantum Hall Skyrmions in Graphene.” Nature Physics, vol. 16, no. 2, Springer Nature, 2019, pp. 154–58, doi:10.1038/s41567-019-0729-8. short: H. Zhou, H. Polshyn, T. Taniguchi, K. Watanabe, A.F. Young, Nature Physics 16 (2019) 154–158. date_created: 2022-01-13T14:45:16Z date_published: 2019-12-16T00:00:00Z date_updated: 2022-01-13T15:34:44Z day: '16' doi: 10.1038/s41567-019-0729-8 extern: '1' intvolume: ' 16' issue: '2' keyword: - General Physics and Astronomy language: - iso: eng month: '12' oa_version: None page: 154-158 publication: Nature Physics publication_identifier: eissn: - 1745-2481 issn: - 1745-2473 publication_status: published publisher: Springer Nature quality_controlled: '1' scopus_import: '1' status: public title: Solids of quantum Hall skyrmions in graphene type: journal_article user_id: ea97e931-d5af-11eb-85d4-e6957dddbf17 volume: 16 year: '2019' ... --- _id: '10664' abstract: - lang: eng text: "Since the discovery of correlated insulators and superconductivity in magic-angle twisted bilayer graphene (tBLG) ([1, 2], JCCM April 2018), theorists have been excitedly pursuing the alluring mix of band topology, symmetry breaking, Mott insulators and superconductivity at play, as well as the potential relation (if any) to high-Tc physics. Now a new stream\r\nof experimental work is arriving which further enriches the story. To briefly recap Episodes 1 and 2 (JCCM April and November 2018), when two graphene layers are stacked with a small rotational mismatch θ, the resulting long-wavelength moire pattern leads to a superlattice potential which reconstructs the low energy band structure. When θ approaches the “magic-angle” θM ∼ 1 ◦, the band structure features eight nearly-flat bands which fill when the electron number per moire unit cell, n/n0, lies between −4 < n/n0 < 4. The bands can be counted as 8 = 2 × 2 × 2: for each spin (2×) and valley (2×) characteristic of monolayergraphene, tBLG has has 2× flat bands which cross at mini-Dirac points." article_processing_charge: No article_type: original author: - first_name: Mathew full_name: Yankowitz, Mathew last_name: Yankowitz - first_name: Shaowen full_name: Chen, Shaowen last_name: Chen - first_name: Hryhoriy full_name: Polshyn, Hryhoriy id: edfc7cb1-526e-11ec-b05a-e6ecc27e4e48 last_name: Polshyn orcid: 0000-0001-8223-8896 - first_name: K. full_name: Watanabe, K. last_name: Watanabe - first_name: T. full_name: Taniguchi, T. last_name: Taniguchi - first_name: David full_name: Graf, David last_name: Graf - first_name: Andrea F. full_name: Young, Andrea F. last_name: Young - first_name: Cory R. full_name: Dean, Cory R. last_name: Dean - first_name: Aaron L. full_name: Sharpe, Aaron L. last_name: Sharpe - first_name: E.J. full_name: Fox, E.J. last_name: Fox - first_name: A.W. full_name: Barnard, A.W. last_name: Barnard - first_name: Joe full_name: Finney, Joe last_name: Finney citation: ama: Yankowitz M, Chen S, Polshyn H, et al. New correlated phenomena in magic-angle twisted bilayer graphene/s. Journal Club for Condensed Matter Physics. 2019;03. doi:10.36471/jccm_february_2019_03 apa: Yankowitz, M., Chen, S., Polshyn, H., Watanabe, K., Taniguchi, T., Graf, D., … Finney, J. (2019). New correlated phenomena in magic-angle twisted bilayer graphene/s. Journal Club for Condensed Matter Physics. Simons Foundation ; University of California, Riverside. https://doi.org/10.36471/jccm_february_2019_03 chicago: Yankowitz, Mathew, Shaowen Chen, Hryhoriy Polshyn, K. Watanabe, T. Taniguchi, David Graf, Andrea F. Young, et al. “New Correlated Phenomena in Magic-Angle Twisted Bilayer Graphene/S.” Journal Club for Condensed Matter Physics. Simons Foundation ; University of California, Riverside, 2019. https://doi.org/10.36471/jccm_february_2019_03. ieee: M. Yankowitz et al., “New correlated phenomena in magic-angle twisted bilayer graphene/s,” Journal Club for Condensed Matter Physics, vol. 03. Simons Foundation ; University of California, Riverside, 2019. ista: Yankowitz M, Chen S, Polshyn H, Watanabe K, Taniguchi T, Graf D, Young AF, Dean CR, Sharpe AL, Fox EJ, Barnard AW, Finney J. 2019. New correlated phenomena in magic-angle twisted bilayer graphene/s. Journal Club for Condensed Matter Physics. 03. mla: Yankowitz, Mathew, et al. “New Correlated Phenomena in Magic-Angle Twisted Bilayer Graphene/S.” Journal Club for Condensed Matter Physics, vol. 03, Simons Foundation ; University of California, Riverside, 2019, doi:10.36471/jccm_february_2019_03. short: M. Yankowitz, S. Chen, H. Polshyn, K. Watanabe, T. Taniguchi, D. Graf, A.F. Young, C.R. Dean, A.L. Sharpe, E.J. Fox, A.W. Barnard, J. Finney, Journal Club for Condensed Matter Physics 03 (2019). date_created: 2022-01-25T15:09:58Z date_published: 2019-02-28T00:00:00Z date_updated: 2022-01-25T15:56:39Z day: '28' doi: 10.36471/jccm_february_2019_03 intvolume: ' 3' language: - iso: eng main_file_link: - open_access: '1' url: https://www.condmatjclub.org/?p=3541 month: '02' oa: 1 oa_version: Published Version publication: Journal Club for Condensed Matter Physics publication_status: published publisher: Simons Foundation ; University of California, Riverside quality_controlled: '1' status: public title: New correlated phenomena in magic-angle twisted bilayer graphene/s type: journal_article user_id: 8b945eb4-e2f2-11eb-945a-df72226e66a9 volume: '03' year: '2019' ... --- _id: '10619' abstract: - lang: eng text: The quantum anomalous Hall (QAH) effect combines topology and magnetism to produce precisely quantized Hall resistance at zero magnetic field. We report the observation of a QAH effect in twisted bilayer graphene aligned to hexagonal boron nitride. The effect is driven by intrinsic strong interactions, which polarize the electrons into a single spin- and valley-resolved moiré miniband with Chern number C = 1. In contrast to magnetically doped systems, the measured transport energy gap is larger than the Curie temperature for magnetic ordering, and quantization to within 0.1% of the von Klitzing constant persists to temperatures of several kelvin at zero magnetic field. Electrical currents as small as 1 nanoampere controllably switch the magnetic order between states of opposite polarization, forming an electrically rewritable magnetic memory. acknowledgement: The authors acknowledge discussions with A. Macdonald, Y. Saito, and M. Zaletel. article_processing_charge: No article_type: original author: - first_name: M. full_name: Serlin, M. last_name: Serlin - first_name: C. L. full_name: Tschirhart, C. L. last_name: Tschirhart - first_name: Hryhoriy full_name: Polshyn, Hryhoriy id: edfc7cb1-526e-11ec-b05a-e6ecc27e4e48 last_name: Polshyn orcid: 0000-0001-8223-8896 - first_name: Y. full_name: Zhang, Y. last_name: Zhang - first_name: J. full_name: Zhu, J. last_name: Zhu - first_name: K. full_name: Watanabe, K. last_name: Watanabe - first_name: T. full_name: Taniguchi, T. last_name: Taniguchi - first_name: L. full_name: Balents, L. last_name: Balents - first_name: A. F. full_name: Young, A. F. last_name: Young citation: ama: Serlin M, Tschirhart CL, Polshyn H, et al. Intrinsic quantized anomalous Hall effect in a moiré heterostructure. Science. 2019;367(6480):900-903. doi:10.1126/science.aay5533 apa: Serlin, M., Tschirhart, C. L., Polshyn, H., Zhang, Y., Zhu, J., Watanabe, K., … Young, A. F. (2019). Intrinsic quantized anomalous Hall effect in a moiré heterostructure. Science. American Association for the Advancement of Science. https://doi.org/10.1126/science.aay5533 chicago: Serlin, M., C. L. Tschirhart, Hryhoriy Polshyn, Y. Zhang, J. Zhu, K. Watanabe, T. Taniguchi, L. Balents, and A. F. Young. “Intrinsic Quantized Anomalous Hall Effect in a Moiré Heterostructure.” Science. American Association for the Advancement of Science, 2019. https://doi.org/10.1126/science.aay5533. ieee: M. Serlin et al., “Intrinsic quantized anomalous Hall effect in a moiré heterostructure,” Science, vol. 367, no. 6480. American Association for the Advancement of Science, pp. 900–903, 2019. ista: Serlin M, Tschirhart CL, Polshyn H, Zhang Y, Zhu J, Watanabe K, Taniguchi T, Balents L, Young AF. 2019. Intrinsic quantized anomalous Hall effect in a moiré heterostructure. Science. 367(6480), 900–903. mla: Serlin, M., et al. “Intrinsic Quantized Anomalous Hall Effect in a Moiré Heterostructure.” Science, vol. 367, no. 6480, American Association for the Advancement of Science, 2019, pp. 900–03, doi:10.1126/science.aay5533. short: M. Serlin, C.L. Tschirhart, H. Polshyn, Y. Zhang, J. Zhu, K. Watanabe, T. Taniguchi, L. Balents, A.F. Young, Science 367 (2019) 900–903. date_created: 2022-01-13T14:21:32Z date_published: 2019-12-19T00:00:00Z date_updated: 2023-02-21T16:00:09Z day: '19' doi: 10.1126/science.aay5533 extern: '1' external_id: arxiv: - '1907.00261' pmid: - '31857492' intvolume: ' 367' issue: '6480' keyword: - multidisciplinary language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/1907.00261 month: '12' oa: 1 oa_version: Preprint page: 900-903 pmid: 1 publication: Science publication_identifier: eissn: - 1095-9203 issn: - 0036-8075 publication_status: published publisher: American Association for the Advancement of Science quality_controlled: '1' related_material: record: - id: '10697' relation: other status: public - id: '10698' relation: other status: public - id: '10699' relation: other status: public scopus_import: '1' status: public title: Intrinsic quantized anomalous Hall effect in a moiré heterostructure type: journal_article user_id: 8b945eb4-e2f2-11eb-945a-df72226e66a9 volume: 367 year: '2019' ... --- _id: '10724' abstract: - lang: eng text: Twisted bilayer graphene (tBLG) near the flat band condition is a versatile new platform for the study of correlated physics in 2D. Resistive states have been observed at several commensurate fillings of the flat miniband, along with superconducting states near half filling. To better understand the electronic structure of this system, we study electronic transport of graphite gated superconducting tBLG devices in the normal regime. At high magnetic fields, we observe full lifting of the spin and valley degeneracy. The transitions in the splitting of this four-fold degeneracy as a function of carrier density indicate Landau level (LL) crossings, which tilted field measurements show occur between LLs with different valley polarization. Similar LL structure measured in two devices, one with twist angle θ=1.08° at ambient pressure and one at θ=1.27° and 1.33GPa, suggests that the dimensionless combination of twist angle and interlayer coupling controls the relevant details of the band structure. In addition, we find that the temperature dependence of the resistance at B=0 shows linear growth at several hundred Ohm/K in a broad range of temperatures. We discuss the implications for modeling the scattering processes in this system. alternative_title: - Bulletin of the American Physical Society article_number: V14.00008 article_processing_charge: No author: - first_name: Hryhoriy full_name: Polshyn, Hryhoriy id: edfc7cb1-526e-11ec-b05a-e6ecc27e4e48 last_name: Polshyn orcid: 0000-0001-8223-8896 - first_name: Yuxuan full_name: Zhang, Yuxuan last_name: Zhang - first_name: Matthew full_name: Yankowitz, Matthew last_name: Yankowitz - first_name: Shaowen full_name: Chen, Shaowen last_name: Chen - first_name: Takashi full_name: Taniguchi, Takashi last_name: Taniguchi - first_name: Kenji full_name: Watanabe, Kenji last_name: Watanabe - first_name: David E. full_name: Graf, David E. last_name: Graf - first_name: Cory R. full_name: Dean, Cory R. last_name: Dean - first_name: Andrea full_name: Young, Andrea last_name: Young citation: ama: 'Polshyn H, Zhang Y, Yankowitz M, et al. Normal state transport in superconducting twisted bilayer graphene. In: APS March Meeting 2019. Vol 64. American Physical Society; 2019.' apa: 'Polshyn, H., Zhang, Y., Yankowitz, M., Chen, S., Taniguchi, T., Watanabe, K., … Young, A. (2019). Normal state transport in superconducting twisted bilayer graphene. In APS March Meeting 2019 (Vol. 64). Boston, MA, United States: American Physical Society.' chicago: Polshyn, Hryhoriy, Yuxuan Zhang, Matthew Yankowitz, Shaowen Chen, Takashi Taniguchi, Kenji Watanabe, David E. Graf, Cory R. Dean, and Andrea Young. “Normal State Transport in Superconducting Twisted Bilayer Graphene.” In APS March Meeting 2019, Vol. 64. American Physical Society, 2019. ieee: H. Polshyn et al., “Normal state transport in superconducting twisted bilayer graphene,” in APS March Meeting 2019, Boston, MA, United States, 2019, vol. 64, no. 2. ista: 'Polshyn H, Zhang Y, Yankowitz M, Chen S, Taniguchi T, Watanabe K, Graf DE, Dean CR, Young A. 2019. Normal state transport in superconducting twisted bilayer graphene. APS March Meeting 2019. APS: American Physical Society, Bulletin of the American Physical Society, vol. 64, V14.00008.' mla: Polshyn, Hryhoriy, et al. “Normal State Transport in Superconducting Twisted Bilayer Graphene.” APS March Meeting 2019, vol. 64, no. 2, V14.00008, American Physical Society, 2019. short: H. Polshyn, Y. Zhang, M. Yankowitz, S. Chen, T. Taniguchi, K. Watanabe, D.E. Graf, C.R. Dean, A. Young, in:, APS March Meeting 2019, American Physical Society, 2019. conference: end_date: 2019-03-08 location: Boston, MA, United States name: 'APS: American Physical Society' start_date: 2019-03-04 date_created: 2022-02-04T12:25:04Z date_published: 2019-03-01T00:00:00Z date_updated: 2022-02-08T10:23:13Z day: '01' extern: '1' intvolume: ' 64' issue: '2' language: - iso: eng main_file_link: - open_access: '1' url: https://meetings.aps.org/Meeting/MAR19/Session/V14.8 month: '03' oa: 1 oa_version: Published Version publication: APS March Meeting 2019 publication_identifier: issn: - 0003-0503 publication_status: published publisher: American Physical Society quality_controlled: '1' status: public title: Normal state transport in superconducting twisted bilayer graphene type: conference user_id: 8b945eb4-e2f2-11eb-945a-df72226e66a9 volume: 64 year: '2019' ... --- _id: '10722' abstract: - lang: eng text: Bilayer graphene, rotationally faulted to ~1.1 degree misalignment, has recently been shown to host superconducting and resistive states associated with the formation of a flat electronic band. While numerous theories exist for the origins of both states, direct validation of these theories remains an outstanding experimental problem. Here, we focus on the resistive states occurring at commensurate filling (1/2, 1/4, and 3/4) of the two lowest superlattice bands. We test theoretical proposals that these states arise due to broken spin—and/or valley—symmetry by performing direct magnetic imaging with nanoscale SQUID-on-tip microscopy. This technique provides single-spin resolved magnetometry on sub-100nm length scales. I will present imaging data from our 4.2K nSOT microscope on graphite-gated twisted bilayers near the flat band condition and discuss the implications for the physics of the commensurate resistive states. alternative_title: - Bulletin of the American Physical Society article_number: L14.00006 article_processing_charge: No author: - first_name: Marec full_name: Serlin, Marec last_name: Serlin - first_name: Charles full_name: Tschirhart, Charles last_name: Tschirhart - first_name: Hryhoriy full_name: Polshyn, Hryhoriy id: edfc7cb1-526e-11ec-b05a-e6ecc27e4e48 last_name: Polshyn orcid: 0000-0001-8223-8896 - first_name: Jiacheng full_name: Zhu, Jiacheng last_name: Zhu - first_name: Martin E. full_name: Huber, Martin E. last_name: Huber - first_name: Andrea full_name: Young, Andrea last_name: Young citation: ama: 'Serlin M, Tschirhart C, Polshyn H, Zhu J, Huber ME, Young A. Direct Imaging of magnetic structure in twisted bilayer graphene with scanning nanoSQUID-On-Tip microscopy. In: APS March Meeting 2019. Vol 64. American Physical Society; 2019.' apa: 'Serlin, M., Tschirhart, C., Polshyn, H., Zhu, J., Huber, M. E., & Young, A. (2019). Direct Imaging of magnetic structure in twisted bilayer graphene with scanning nanoSQUID-On-Tip microscopy. In APS March Meeting 2019 (Vol. 64). Boston, MA, United States: American Physical Society.' chicago: Serlin, Marec, Charles Tschirhart, Hryhoriy Polshyn, Jiacheng Zhu, Martin E. Huber, and Andrea Young. “Direct Imaging of Magnetic Structure in Twisted Bilayer Graphene with Scanning NanoSQUID-On-Tip Microscopy.” In APS March Meeting 2019, Vol. 64. American Physical Society, 2019. ieee: M. Serlin, C. Tschirhart, H. Polshyn, J. Zhu, M. E. Huber, and A. Young, “Direct Imaging of magnetic structure in twisted bilayer graphene with scanning nanoSQUID-On-Tip microscopy,” in APS March Meeting 2019, Boston, MA, United States, 2019, vol. 64, no. 2. ista: 'Serlin M, Tschirhart C, Polshyn H, Zhu J, Huber ME, Young A. 2019. Direct Imaging of magnetic structure in twisted bilayer graphene with scanning nanoSQUID-On-Tip microscopy. APS March Meeting 2019. APS: American Physical Society, Bulletin of the American Physical Society, vol. 64, L14.00006.' mla: Serlin, Marec, et al. “Direct Imaging of Magnetic Structure in Twisted Bilayer Graphene with Scanning NanoSQUID-On-Tip Microscopy.” APS March Meeting 2019, vol. 64, no. 2, L14.00006, American Physical Society, 2019. short: M. Serlin, C. Tschirhart, H. Polshyn, J. Zhu, M.E. Huber, A. Young, in:, APS March Meeting 2019, American Physical Society, 2019. conference: end_date: 2019-03-08 location: Boston, MA, United States name: 'APS: American Physical Society' start_date: 2019-03-04 date_created: 2022-02-04T11:54:21Z date_published: 2019-03-01T00:00:00Z date_updated: 2022-02-08T10:25:30Z day: '01' extern: '1' intvolume: ' 64' issue: '2' language: - iso: eng main_file_link: - open_access: '1' url: https://meetings.aps.org/Meeting/MAR19/Session/L14.6 month: '03' oa: 1 oa_version: Published Version publication: APS March Meeting 2019 publication_identifier: issn: - 0003-0503 publication_status: published publisher: American Physical Society quality_controlled: '1' status: public title: Direct Imaging of magnetic structure in twisted bilayer graphene with scanning nanoSQUID-On-Tip microscopy type: conference user_id: 8b945eb4-e2f2-11eb-945a-df72226e66a9 volume: 64 year: '2019' ...