Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session D21: Moire Beyond Magic-Angle II |
Hide Abstracts |
Sponsoring Units: DCMP Chair: Guo Yu, Princeton University Room: Room 213 |
Monday, March 6, 2023 3:00PM - 3:12PM |
D21.00001: Twelve-fold degenerate quantum Hall state in near 30°-twisted bilayer graphene Kuo-En Chang, Sheng-Chin Ho, Yu-Chiang Hsieh, Chiu-Hua Huang, Ching-Hua Kao, Li-An Wen, Kenji Watanabe, Takashi Taniguchi, Tse-Ming Chen Twisted bilayer graphene (tBLG) has attracted tremendous interest but so far has mostly focused on the use of small twist angles. One of the major reasons is that the interlayer coupling between the incommensurate layers, which is normally the case of a large-angle-tBLG, was generally negligible and hence exotic quantum phases of matter are rarely expected. However, when the twist angle is rotated to near 30°, it becomes a very different story. The tBLG forms into dodecagonal quasicrystal with electronic properties distinct from the conventional periodic tBLG [1, 2]. It remains a challenge to explore these quasicrystalline tBLG states through the electrical transport measurements. Here, we use dry transfer methods to fabricate near 30°-tBLG devices and observe an anomalous anti-symmetry of quantum Hall plateaus. Moreover, a robust 12-fold degeneracy is observed in the quantum Hall regime up to ~60 K in both electron and hole transport. |
Monday, March 6, 2023 3:12PM - 3:24PM |
D21.00002: Ultra high resolution potential imaging using the quantum twisting microscope Dahlia R Klein, Uri Zondiner, Takashi Taniguchi, Kenji Watanabe, Shahal Ilani Imaging the local electrostatic potential of quantum materials plays a crucial role in understanding charge order, broken symmetries, and phase transitions. Until now, the most sensitive tool for such imaging is the scanning single electron transistor (SET), which has unearthed a wealth of information in van der Waals systems. However, it is spatially limited by the lithographically defined dimensions of a quantum dot on a tip or cantilever hovering above the sample of interest, resulting in a resolution on the order of 100 nanometers. In this talk, we introduce a new experimental approach to image the electrostatic potential in 2D systems, achieving two orders of magnitude improvement in spatial resolution and operating from room temperature down to cryogenic temperatures. This scanning charge detector is built from the same platform as the quantum twisting microscope (QTM): we assemble in situ van der Waals heterostructures by bringing 2D tip and sample surfaces into contact while simultaneously scanning the sample. This geometry overcomes the limits of previous scanning SETs, enabling resolution of about 1 nanometer. Our technique promises to open up wide-ranging opportunities for direct nanoscale visualization of electronic phenomena with unprecedented spatial resolution in a number of 2D systems, including imaging topological edge states and within moiré length scales. |
Monday, March 6, 2023 3:24PM - 3:36PM |
D21.00003: Technical advances in high pressure measurements of twisted graphene heterostructures Manish A Kumar, Yingqi Wang, Alexander Sanchez, Kenji Watanabe, Takashi Taniguchi, Xiaodong Xu, Matthew A Yankowitz Hydrostatic pressure can modify the band structure of twisted graphene by reducing the interlayer separation, thus enabling the generation of flat bands even at non-optimal twist angles. Previously, pressure has been used to tune superconductivity and other correlated states in twisted bilayer graphene. However, despite being a valuable tuning knob, pressure measurements are still quite challenging due to the limited sample space inside the pressure cell, and difficulties in mounting the sample and establishing electrical connections to numerous contacts and gates. To address these issues, we have designed a custom printed circuit board (PCB) with gold pads on one side and solder cups on the other. The sample is mounted in the center of the PCB, and electrical connection is established by wire bonding rather than hand-pasting wires. The PCB additionally acts as a connection terminal that routes 16 wires to the device within a tight sample space of 3 mm diameter. The PCB has a central through hole enabling the sample to be anchored in place with a stiff tungsten wire. We will additionally report the status of ongoing work enabled by these technical advances, in which we investigate the pressure-tuned properties of various graphene-based moiré heterostructures. |
Monday, March 6, 2023 3:36PM - 3:48PM |
D21.00004: Gate-tunable Magneto Transport in Consecutively-twisted Trilayer Graphene Moire of Moire Superlattices Wei Ren, Konstantin Davydov, Xi Zhang, Ziyan Zhu, Kenji Watanabe, Takashi Taniguchi, Efthimios Kaxiras, Mitchell Luskin, Ke Wang Correlated insulating states and the transport signature of superconductivity have been reported in twisted trilayer graphene Moire of Moire superlattices [1]. Towards a further understanding of its underlying mechanism, we study the low-temperature magneto-transport in a dual-gated twisted trilayer graphene device and its dependence on an out-of-plane electric field. We comprehensively examine the role of each monolayer graphene layer in determining the rich electronic structure of the Moire of Moire superlattices. [1] Zhang, X. et al. Phys. Rev. Lett. (2021) |
Monday, March 6, 2023 3:48PM - 4:00PM |
D21.00005: Moiré effects in twisted graphene/graphite heterostructures Ellis Thompson, Dacen Waters, Esmeralda Arreguin-Martinez, Manato Fujimoto, Yafei Ren, Kenji Watanabe, Takashi Taniguchi, Ting Cao, Di Xiao, Matthew A Yankowitz Moiré vdW heterostructures often host flat and isolated electronic bands which lead to strongly correlated states including superconductivity and magnetism. Ultra-thin twisted graphene heterostructures assembled from monolayer and bilayer constituents have been studied extensively over the past few years, but it is unknown what types of moiré effects emerge in the limit of bulk graphite (≥10 layers). We perform transport measurements of dual gated twisted monolayer graphene-graphite devices and find that the resulting two-dimensional surface moiré potential fundamentally changes the electronic properties of the entire structure. At low magnetic fields, we observe a single resistive peak that moves in an unusual zig-zag trajectory as a function of the top and bottom gate voltages. We observe a similar zig-zag evolution of quantum oscillations emerging at higher fields, which differ substantially depending on which gate is tuned. These measurements indicate that doping of the entire bulk graphite oscillates periodically as the moiré surface bands are filled. The unique properties of these moiré/bulk hybrid structures derive from the semimetallic nature of graphite, establishing a new class of moiré materials with mixed dimensionality. |
Monday, March 6, 2023 4:00PM - 4:12PM |
D21.00006: Hysteresis and anomalous gate screening in aligned graphene/BN systems Dacen Waters, Ellis Thompson, Esmeralda Arreguin-Martinez, Anna Okounkova, Jordan M Fonseca, Kenji Watanabe, Takashi Taniguchi, Xiaodong Xu, Matthew A Yankowitz Moiré potentials in few-layer graphene aligned to boron nitride (BN) can generate a variety of emergent physical phenomena. As a prominent recent example, anomalous gate screening and hysteresis of the electrical resistance have been observed in bilayer graphene aligned to BN [1]. However, the mechanism underlying this effect and the precise role of the moiré potential remain unclear. In this work, we perform a systematic study of few-layer graphene devices in which we control the alignment of both the top and bottom BN with the graphene. We probe the role of the moiré potential by surveying all possible BN/graphene/BN alignment configurations, distinguishing between and alignment using Raman spectroscopy and second harmonic generation. We find that the hysteresis persists above room temperature, calling into question the role of correlations in establishing this effect. Our work is a significant step towards both understanding the nature of this phenomenon and implementing these devices for useful electronics applications. |
Monday, March 6, 2023 4:12PM - 4:24PM |
D21.00007: Time-Reversal Even Charge Hall Effect from Twisted Interface Coupling Dawei Zhai, Cong Chen, Cong Xiao, Wang Yao We discover a linear charge Hall effect in a non-isolated two-dimensional crystal with time reversal symmetry. The restriction by Onsager relation on having a linear Hall response is lifted by interfacial coupling with an adjacent layer, where the overall chiral symmetry requirement is fulfilled by a twisted stacking. This is the first scenario for realizing a time-reversal even Hall effect that was usually thought to be forbidden. We reveal the underlying band geometric quantity as the momentum-space vorticity of the layer current. We demonstrate this effect in twisted bilayer graphene and twisted homobilayer transition metal dichalcogenides with a wide range of twist angles. We find giant Hall ratios under experimentally practical conditions and show gate voltage controlled on-off switch. This work reveals novel Hall physics in chiral structures and opens a new direction of layertronics that exploits the quantum nature of layer degree of freedom to uncover exciting effects. |
Monday, March 6, 2023 4:24PM - 4:36PM |
D21.00008: Intrinsic planar Hall effect induced from the layer pseudospin Huiyuan Zheng, Dawei Zhai, Cong Xiao, Wang Yao The planar Hall effect (PHE) is an intriguing orbital magnetoelectric effect of electrons in coplanar electric and magnetic fields. Most existing proposals require strong spin-orbit coupling and the response manifests in the symmetric part of the conductivity tensor, which does not contribute to a dissipationless Hall current. Here we propose a novel mechanism to realize an intrinsic PHE by utilizing the layer pseudospin that is unique to layered van der Waals materials. In a bilayer structure, the layer pseudospin and interlayer coupling endow electrons with an effective in-plane magnetic moment. A planar magnetic field can couple to the in-plane magnetic moment, thus affects the orbital motion of electrons. The intrinsic PHE conductivity has a geometric origin rooted in the Berry curvature. Symmetry analysis shows that such an intrinsic PHE is linear in the magnetic field in bilayers without rotational symmetry, which also complies with the antisymmetric and dissipationless property of a genuine Hall effect. We show sizeable intrinsic PHE in widely studied bilayer materials, including strained twisted bilayer graphene and homobilayer transition metal dichalcogenides. Strain tuning and bias control of the intrinsic PHE are also explored. |
Monday, March 6, 2023 4:36PM - 4:48PM |
D21.00009: Controlling the Electronic Structure of Twisted Bilayer Graphene Devices Nicholas G Dale, Iqbal B Utama, Sihan Zhao, Kyunghoon Lee, Takashi Taniguchi, Kenji Watanabe, Christopher Jozwiak, Roland Koch, Eli Rotenberg, Aaron Bostwick, feng wang, Alessandra Lanzara Flat bands in twisted bilayer graphene host many intriguing correlated phases including unconventional superconductivity and chern insulation. How the doping and displacement field-dependent properties of these bands affect the emergence of such symmetry-breaking phases remains an open fundamental question. Here, using angle resolved photoemission spectroscopy, we study the effects of many-body interactions and displacement field on the band structure of twisted bilayer graphene field-effect devices. |
Monday, March 6, 2023 4:48PM - 5:00PM Author not Attending |
D21.00010: Moir´e flat bands and interfacial charge polarization in lattice relaxed twisted bilayer hexagonal boron nitride Li Fengping We study the electronic structure and interfacial charge polarization of twisted bilayer hexagonal boron nitride (t2BN) as a function of twist angle and perpendicular electric fields. Our calculations rely on exact exchange and random phase approximation fitted force fields for the atomistic relaxations, and on first principles calculations informed intralayer and interlayer tight-binding hopping terms for the electronic structure. The sizeable interfacial charge polarization for h-BN bilayers near 0? parallel alignment can be understood from the maximal local interlayer dipoles forming at AB and BA stacking sites, while it is generally suppressed near 60? antiparallel alignment. Perpendicular electric fields modify the local interlayer distances and the local AB or BA stacking areas impacting the band gaps, band widths and local interlayer charge distributions associated with the nearly flat low energy bands. |
Monday, March 6, 2023 5:00PM - 5:12PM |
D21.00011: Commensuration torques and lubricity in double moire systems Jeil Jung, Nicolas Leconte, Jiaqi An, Youngju Park We study the commensuration torques and layer sliding energetics of double moire systems exemplified through twisted trilayer graphene (t3G) and twisted bilayer graphene on hexagonal boron nitride (t2G/BN). Lattice relaxations show that the twist angles leading to commensurate moire patterns are energetically favored typically by a fraction of meV/atom when the t2G interface angle is around ~1°. For aligned moire patterns, we find sliding energy barriers of similar magnitude and minimization is achieved in alternating twist t3G when top-bottom layers are AA stacked and breaks mirror symmetry, while the favored geometries for t2G/BN have AA top-bottom layer local stacking for type I and BA stacking for type II. When the moire patterns are misaligned we restore moire superlubricity where the sliding energy landscape amplitude is suppressed by several orders of magnitude with energy barriers of the order of ~10-4 meV/atom, indicating that aligning moire pattern angles through rotation precedes over sliding in the double moire commensuration process. |
Monday, March 6, 2023 5:12PM - 5:24PM |
D21.00012: Strong correlations in ABC-stacked trilayer graphene: Moiré is important Adarsh S Patri, Senthil Todadri Recent experiments on multilayer graphene materials have discovered a plethora of correlated phases, including ferromagnetism and superconductivity, in the absence of a moiré potential. These findings pose an intriguing question of whether an underlying moiré potential plays a key role in determining the phases realizable in tunable two-dimensional quantum materials, or whether it merely acts as a weak periodic potential that perturbs an underlying correlated many body state. In this work, employing a Hartree-Fock mean field analysis, we examine this question theoretically by quantitatively studying the effects of an hexagonal Boron Nitride (h-BN) substrate on ABC-stacked trilayer graphene (ABC-TLG). Our findings highlight the importance of interactions in renormalizing the electronic bandstructure, and the key role played by the moiré potential in determining the strong correlation physics. |
Monday, March 6, 2023 5:24PM - 5:36PM |
D21.00013: Valley-protected one-dimensional states in small-angle twisted bilayer graphene Jort Verbakel Theory predicts that the application of an electric eld breaks the inversion symmetry of AB and BA stacked domains in twisted bilayer graphene, resulting in the formation of a triangular |
Monday, March 6, 2023 5:36PM - 5:48PM Author not Attending |
D21.00014: Electronic Interactions in Graphene/WS2 Assisted by the Interlayer Rotation Angle Cecilia Noguez, Francisco Hidalgo, Francisco Sanchez-Ochoa Understanding the electronic properties modulation in graphene/tungsten disulfide (G/WS2) at different interlayer angles is essential for promising building blocks of two-dimensional (2D) heterostructures. In this talk, we discuss results for G/WS2 heterostructures with four different interlayer angles studied using periodic first-principles calculations and an unfolding method to decipher the supercell crowded-band structure. Electronic mini-gaps of different sizes, band splittings, and band hybridizations are identified because of the interactions between out-of-plane orbitals from both layers. These electronic changes are modulated depending on the interlayer angle, the energy window, and the space region. At the same time, replicas emerge because of the superperiodic potential associated with moiré patterns that also modify such electronic changes, inducing new electronic repulsions or avoided crossings. Therefore, mini-gaps energy values and positions are intrinsically related to the interlayer angle. Finally, it is anticipated that these results might be essential for designing the optoelectronic properties of 2D heterostructures. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700