--- _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' ... --- _id: '10725' abstract: - lang: eng text: Bilayer graphene with ~ 1.1 degrees twist mismatch between the layers hosts a low energy flat band in which the Coulomb interaction is large relative to the bandwidth, promoting correlated insulating states at half band filling, and superconducting (SC) phases with dome-like structure neighboring correlated insulating states. Here we show measurements of a dual-graphite-gated twisted bilayer graphene device, which minimizes charge inhomogeneity. We observe new correlated phases, including for the first time a SC pocket near half-filling of the electron-doped band and resistive states at quarter-filling of both bands that emerge in a magnetic field. Changing the layer polarization with vertical electric field reveals an unexpected competition between SC and correlated insulator phases, which we interpret to result from differences in disorder of each graphene layer and underscores the spatial inhomogeneity like twist angle as a significant source of disorder in these devices [1]. alternative_title: - Bulletin of the American Physical Society article_number: R14.00004 article_processing_charge: No author: - first_name: Shaowen full_name: Chen, Shaowen last_name: Chen - first_name: Matthew full_name: Yankowitz, Matthew last_name: Yankowitz - first_name: Hryhoriy full_name: Polshyn, Hryhoriy id: edfc7cb1-526e-11ec-b05a-e6ecc27e4e48 last_name: Polshyn orcid: 0000-0001-8223-8896 - first_name: Kenji full_name: Watanabe, Kenji last_name: Watanabe - first_name: Takashi full_name: Taniguchi, Takashi last_name: Taniguchi - first_name: David E. full_name: Graf, David E. last_name: Graf - first_name: Andrea full_name: Young, Andrea last_name: Young - first_name: Cory R. full_name: Dean, Cory R. last_name: Dean citation: ama: 'Chen S, Yankowitz M, Polshyn H, et al. Correlated insulating and superconducting phases in twisted bilayer graphene. In: APS March Meeting 2019. Vol 64. American Physical Society; 2019.' apa: 'Chen, S., Yankowitz, M., Polshyn, H., Watanabe, K., Taniguchi, T., Graf, D. E., … Dean, C. R. (2019). Correlated insulating and superconducting phases in twisted bilayer graphene. In APS March Meeting 2019 (Vol. 64). Boston, MA, United States: American Physical Society.' chicago: Chen, Shaowen, Matthew Yankowitz, Hryhoriy Polshyn, Kenji Watanabe, Takashi Taniguchi, David E. Graf, Andrea Young, and Cory R. Dean. “Correlated Insulating and Superconducting Phases in Twisted Bilayer Graphene.” In APS March Meeting 2019, Vol. 64. American Physical Society, 2019. ieee: S. Chen et al., “Correlated insulating and superconducting phases in twisted bilayer graphene,” in APS March Meeting 2019, Boston, MA, United States, 2019, vol. 64, no. 2. ista: 'Chen S, Yankowitz M, Polshyn H, Watanabe K, Taniguchi T, Graf DE, Young A, Dean CR. 2019. Correlated insulating and superconducting phases in twisted bilayer graphene. APS March Meeting 2019. APS: American Physical Society, Bulletin of the American Physical Society, vol. 64, R14.00004.' mla: Chen, Shaowen, et al. “Correlated Insulating and Superconducting Phases in Twisted Bilayer Graphene.” APS March Meeting 2019, vol. 64, no. 2, R14.00004, American Physical Society, 2019. short: S. Chen, M. Yankowitz, H. Polshyn, K. Watanabe, T. Taniguchi, D.E. Graf, A. Young, C.R. Dean, 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: 2022-02-04T13:48:04Z date_published: 2019-03-01T00:00:00Z date_updated: 2022-02-08T10:24:13Z 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/R14.4 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' related_material: link: - relation: used_in_publication url: https://arxiv.org/abs/1808.07865 status: public title: Correlated insulating and superconducting phases in twisted bilayer graphene type: conference user_id: 8b945eb4-e2f2-11eb-945a-df72226e66a9 volume: 64 year: '2019' ... --- _id: '10723' abstract: - lang: eng text: In monolayer graphene, the interplay of electronic correlations with the internal spin- and valley- degrees of freedom leads to a complex phase diagram of isospin symmetry breaking at high magnetic fields. Recently, Wei et al. (Science (2018)) demonstrated that spin waves can be electrically generated and detected in graphene heterojunctions, allowing direct experiment access to the spin degree of freedom. Here, we apply this technique to high quality graphite-gated graphene devices showing robust fractional quantum Hall phases and isospin phase transitions. We use an edgeless Corbino geometry to eliminate the contributions of edge states to the spin-wave mediated nonlocal voltage, allowing unambiguous identification of spin wave transport signatures. Our data reveal two phases within the ν = 1 plateau. For exactly ν=1, charge is localized but spin waves propagate freely while small carrier doping completely quenches the low-energy spin-wave transport, even as those charges remain localized. We identify this new phase as a spin textured electron solid. We also find that spin-wave transport is modulated by phase transitions in the valley order that preserve spin polarization, suggesting that this technique is sensitive to both spin and valley order. article_number: P01.00004 article_processing_charge: No author: - first_name: Haoxin full_name: Zhou, Haoxin 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: Takashi full_name: Tanaguchi, Takashi last_name: Tanaguchi - first_name: Kenji full_name: Watanabe, Kenji last_name: Watanabe - first_name: Andrea full_name: Young, Andrea last_name: Young citation: ama: 'Zhou H, Polshyn H, Tanaguchi T, Watanabe K, Young A. Spin wave transport through electron solids and fractional quantum Hall liquids in graphene. In: APS March Meeting 2019. Vol 64. American Physical Society; 2019.' apa: 'Zhou, H., Polshyn, H., Tanaguchi, T., Watanabe, K., & Young, A. (2019). Spin wave transport through electron solids and fractional quantum Hall liquids in graphene. In APS March Meeting 2019 (Vol. 64). Boston, MA, United States: American Physical Society.' chicago: Zhou, Haoxin, Hryhoriy Polshyn, Takashi Tanaguchi, Kenji Watanabe, and Andrea Young. “Spin Wave Transport through Electron Solids and Fractional Quantum Hall Liquids in Graphene.” In APS March Meeting 2019, Vol. 64. American Physical Society, 2019. ieee: H. Zhou, H. Polshyn, T. Tanaguchi, K. Watanabe, and A. Young, “Spin wave transport through electron solids and fractional quantum Hall liquids in graphene,” in APS March Meeting 2019, Boston, MA, United States, 2019, vol. 64, no. 2. ista: 'Zhou H, Polshyn H, Tanaguchi T, Watanabe K, Young A. 2019. Spin wave transport through electron solids and fractional quantum Hall liquids in graphene. APS March Meeting 2019. APS: American Physical Society vol. 64, P01.00004.' mla: Zhou, Haoxin, et al. “Spin Wave Transport through Electron Solids and Fractional Quantum Hall Liquids in Graphene.” APS March Meeting 2019, vol. 64, no. 2, P01.00004, American Physical Society, 2019. short: H. Zhou, H. Polshyn, T. Tanaguchi, K. Watanabe, 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: 2022-02-04T12:14:02Z date_published: 2019-03-01T00:00:00Z date_updated: 2022-02-04T13:59:47Z 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/P01.4 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: Spin wave transport through electron solids and fractional quantum Hall liquids in graphene type: conference user_id: 8b945eb4-e2f2-11eb-945a-df72226e66a9 volume: 64 year: '2019' ...