Bulletin of the American Physical Society
APS March Meeting 2024
Monday–Friday, March 4–8, 2024; Minneapolis & Virtual
Session Y41: Discovery and Optimization of Novel Magnetism and Superconductivity in Rhombohedral Graphene MultilayersInvited
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Sponsoring Units: DCMP Chair: Fan Zhang, The University of Texas at Dallas Room: Ballroom A |
Friday, March 8, 2024 8:00AM - 8:36AM |
Y41.00001: Magnetism and superconductivity in rhombohedral graphene multilayers: triplet superconductivity, intervalley coherence, and spin orbit coupling Invited Speaker: Andrea F Young The noninteracting band structure of rhombohedral graphene multilayers is characterized by displacement field tunable van Hove singularities where the single particles density of states diverges. When the system is doped into the center of these singularities, a variety of interaction driven instabilities are observed, including magnetic and superconducting states are observed. Crucially, rhombohedral graphene multilayers can be fabricated with low disorder and high reproducibility. This allows carefully controlled experiments to probe both the interplay of intrinsic symmetry breaking terms as well as extrinsic substrate effects such as a periodic potential or enhanced spin orbit coupling. I will review experiments on these systems, focusing on experimental constraints imposed on the ground state phase diagram by transport, magnetization, and compressibility measurements in rhombohedral trilayer graphene. |
Friday, March 8, 2024 8:36AM - 9:12AM |
Y41.00002: Superconductivity in Bernal Bilayer Graphene Enhanced by Spin-Orbit Coupling Invited Speaker: Stevan Nadj-Perge Induced spin-orbit coupling (SOC) in Bernal Bilayer Graphene (BLG) placed on top of monolayer tungsten diselenide (WSe2) drastically changes its phase diagram. Most prominently, the SOC stabilizes the superconductivity in the system over a broad region of parameter space and increases the critical temperature by an order of magnitude. In this talk, I will review our recent experiments on this platform, where we tuned SOC by controlling the BLG-WSe2 twist angle and, besides superconductivity, looked into more subtle changes in the electronic phase diagram obtained by a combination of transport and capacitance measurements as well as theoretical modeling. We will also discuss the nature of the superconducting parent phase in the context of spin-valley-mixed states and our observations. |
Friday, March 8, 2024 9:12AM - 9:48AM |
Y41.00003: Orbital multiferroicity and coexistence of two strongly correlated regimes in rhombohedral graphene pentalayer Invited Speaker: Long Ju
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Friday, March 8, 2024 9:48AM - 10:24AM |
Y41.00004: Cascade of correlated phases in the vicinity of tuneable van Hove singularities in Bernal bilayer graphene Invited Speaker: Anna M Seiler The naturally occurring Bernal bilayer graphene has a complex low-energy band structure. It hosts electric-field-controlled Lifshitz transitions where the density of states diverges. In the vicinity of these tunable van-Hove-singularities, we observe experimental signatures consistent with various interaction-driven phases, including the fractional metals of Stoner type [1, 2]. More prominently, we find competing nontrivial insulating and metallic phases at hole doping that exhibit intriguing temperature dependences and nonlinear I-V characteristics at zero magnetic field [1]. |
Friday, March 8, 2024 10:24AM - 11:00AM |
Y41.00005: Interaction-induced gap and gate-tunable magnetism in rhombohedral graphene Invited Speaker: Chun Ning Lau The flat dispersion in rhombohedral stackedN-layer graphene, whereE~kN, gives rise to diverging (forN>2) density of states that are unstable to electronic interactions, leading to the formation of electronic states with spontaneous broken symmetries. In free-standing samples, the electronic interactions are further strengthened due to the absence of screening. Using transport measurements on suspended dual-gated devices, we observe an insulating ground state with a large interaction-induced gap up to 80 meV at half filling. This gapped state can be enhanced by a perpendicular magnetic field, and suppressed by an interlayer potential, carrier density, or a critical temperature of ~40 K, and is most likely a layer antiferromagnet[1]. Upon small doping, we observe prominent conductance hysteresis and giant magnetoconductance that exceeds 1000% as a function of magnetic fields. Both phenomena are tunable by density and temperature, and disappear atn>1012cm-2orT>5K. These results are confirmed by first principles calculations, which indicate the formation of a half-metallic state in doped r-FLG, in which the magnetization is tunable by electric field. Our results demonstrate that magnetism and spin polarization, arising from the strong electronic interactions in flat bands, emerge in a system composed entirely of carbon atoms[2]. In the future, different ground states are expected to be stabilized by substrate engineering.
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