Article
Materials Science, Multidisciplinary
Maria Spethmann, Carsten Honerkamp, Dante M. Kennes
Summary: In this study, magnetic ordering tendencies of encapsulated bilayer graphene forming a moire structure with hexagonal boron nitride layers are analyzed using the random phase approximation. The dominant magnetic ordering instability is found to be uniformly antiferromagnetic in the charge neutral case. Mean-field calculations indicate that the critical Hubbard interaction required to induce magnetic order is slightly higher in systems where the moire structure has caused a band gap opening.
Article
Multidisciplinary Sciences
Myungchul Oh, Kevin P. Nuckolls, Dillon Wong, Ryan L. Lee, Xiaomeng Liu, Kenji Watanabe, Takashi Taniguchi, Ali Yazdani
Summary: Recent studies on magic-angle twisted bilayer graphene (MATBG) have shown that the superconductivity in MATBG may not be described by the conventional BCS theory, but rather resembles a non-BCS mechanism due to the large density of states in its flat bands. This suggests that the pairing mechanism in MATBG may be unconventional and different from that of conventional superconductors.
Article
Multidisciplinary Sciences
Christopher R. Anderson, Noel Natera-Cordero, Victor H. Guarochico-Moreira, Irina V. Grigorieva, Ivan J. Vera-Marun
Summary: We investigate the controllability of charge and spin transport in high-quality bilayer graphene encapsulated with hBN and contacted via 1D spin injectors at room temperature. We demonstrate that spin transport in this device architecture is measurable and its parameters can be modulated by opening a band gap through a perpendicular displacement field. The modulation of spin current is primarily achieved by controlling the spin relaxation time with the displacement field, showcasing the fundamental operation of a spin-based field-effect transistor.
SCIENTIFIC REPORTS
(2023)
Article
Chemistry, Physical
Ningning Xuan, Aozhen Xie, Bing Liu, Zhengzong Sun
Summary: Bilayer graphene (BLG) has attracted significant research interest for its tunable physical properties dependent on twisted angles and interlayer interaction. This article focuses on the study of BLG single crystals with representative twisted angles of approximately 0 degrees and approximately 30 degrees, grown by chemical vapor deposition (CVD). The surface potentials of pristine BLG single crystals indicate that the surface potential difference between single layer graphene (SLG) and BLG is lower for approximately 0 degrees compared to approximately 30 degrees. Additionally, reversible tuning of the electrical coupling and properties of BLG is achieved through diazonium salts reaction and nitrogen doping, resulting in a wide range of surface potential tuning from 0 to 50 mV.
Article
Nanoscience & Nanotechnology
Eike Icking, Luca Banszerus, Frederike Woertche, Frank Volmer, Philipp Schmidt, Corinne Steiner, Stephan Engels, Jonas Hesselmann, Matthias Goldsche, Kenji Watanabe, Takashi Taniguchi, Christian Volk, Bernd Beschoten, Christoph Stampfer
Summary: Controlling both the charge carrier density and the band gap is crucial for various applications of semiconductors. Graphite-gated bilayer graphene exhibits extremely low disorder and ultraclean tunable band gaps, making a wide range of semiconductor applications possible.
ADVANCED ELECTRONIC MATERIALS
(2022)
Article
Chemistry, Multidisciplinary
Shuichi Iwakiri, Folkert K. de Vries, Elias Portoles, Giulia Zheng, Takashi Taniguchi, Kenji Watanabe, Thomas Ihn, Klaus Ensslin
Summary: In this study, we have successfully implemented an electron interferometer controlled purely by electrostatic gating in encapsulated bilayer graphene. The device demonstrates a coherence length of many microns and seamless tunability of Aharonov-Bohm oscillations and carrier types. The gate-defined ring geometry also has the potential to explore correlated quantum states in twisted bilayer graphene interferometers.
Article
Multidisciplinary Sciences
Fabian R. Geisenhof, Felix Winterer, Anna M. Seiler, Jakob Lenz, Tianyi Xu, Fan Zhang, R. Thomas Weitz
Summary: In this study, a state with a conductance of 2e(2)h(-1) in bilayer graphene was discovered, exhibiting magnetic hysteresis and QAH behavior driven by orbital magnetism that can be tuned via electric and magnetic fields. The observed octet of QAH phases in bilayer graphene displays peculiar ferrimagnetic and ferrielectric order characterized by quantized anomalous charge, spin, valley and spin-valley Hall behavior.
Article
Materials Science, Multidisciplinary
Xi Wu, Fawei Zheng, Feiyu Kang, Jia Li
Summary: By using density functional theory calculations, we have identified the stable intercalated structure and the evolution of band structures in the intercalation process of Li into bilayer graphene. Our work shows that the Dirac cone of bilayer graphene can be modulated by using the generalized N/ N/ Kekule order, which opens a gap or splits the electron and hole pocket, contributed by the Kekule-O and Kekule-Y distortion respectively. This study provides valuable insights for the investigation of Li-intercalated bilayer graphene in experiments.
Article
Nanoscience & Nanotechnology
Talieh S. Ghiasi, Alexey A. Kaverzin, Avalon H. Dismukes, Dennis K. de Wal, Xavier Roy, Bart J. van Wees
Summary: The coupling of bilayer graphene with the 2D interlayer antiferromagnetic CrSBr enables the active generation of spin currents in graphene, benefiting ultracompact spintronic devices. The strong spin-charge coupling in graphene and the high sensitivity of spin transport to the adjacent antiferromagnet's magnetization allow for the read-out of a single magnetic sublattice.
NATURE NANOTECHNOLOGY
(2021)
Article
Multidisciplinary Sciences
Jianbo Yin, Cheng Tan, David Barcons-Ruiz, Iacopo Torre, Kenji Watanabe, Takashi Taniguchi, Justin C. W. Song, James Hone, Frank H. L. Koppens
Summary: This study reports the direct observation of in situ tunable valley-selective Hall effect and demonstrates the control of geometric phase of electrons using an out-of-plane electric field. The researchers used high-quality bilayer graphene and circularly polarized midinfrared light to observe the optically induced valley population and found a significantly larger valley-selective Hall effect compared to molybdenum disulfide. By monitoring the valley-selective Hall conductivity, the researchers studied the evolution of Berry curvature with bandgap.
Article
Chemistry, Multidisciplinary
Hira Ali, Llorenc Serra
Summary: We investigate the impact of a local potential shift induced by a side electrode on the properties of the edge modes of bilayer graphene at the boundary between gapped and ungapped regions. It is found that a potential shift near the gapped-ungapped boundary leads to the emergence of unprotected edge modes that propagate in both directions along the boundary. These counterpropagating edge modes allow for edge backscattering, in contrast to the valley-momentum-locked edge modes. Additionally, we analyze the conductance of a bilayer graphene wire in the presence of finger-gate electrodes and observe strong asymmetries, energy inversion, and deviations from conductance quantization, which can be explained by the gate-induced unprotected edge modes.
Article
Physics, Multidisciplinary
Cheng Tan, Davoud Adinehloo, James Hone, Vasili Perebeinos
Summary: The weak acoustic phonon scattering in graphene monolayer leads to high mobilities even at room temperatures. We identify the dominant role of shear phonon mode scattering on the carrier mobility in AB-stacked graphene bilayer, which is absent in monolayer graphene. The surface polar phonon scattering from a boron nitride substrate contributes significantly to the measured mobilities at elevated temperatures.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Multidisciplinary
Chunli Huang, Nemin Wei, Wei Qin, Allan H. MacDonald
Summary: The study presents a theory of superconductivity in twisted bilayer graphene, where attraction is generated between electrons on the same honeycomb sublattice near a sublattice polarization instability, leading to spin-polarized valley singlet Cooper pairs. Superconductivity occurs over a wide range of filling fraction, and can be suppressed by controlling sublattice polarizability or moire band filling to favor valley polarization.
PHYSICAL REVIEW LETTERS
(2022)
Article
Chemistry, Multidisciplinary
Yanbo Xin, Qin Gao, Jiangshun Huang, Juan Gao, Xueli Geng, Hongliang Shi, Mei Wang, Zhisong Xiao, Paul K. Chu, Anping Huang
Summary: In this study, asymmetric double-layer graphene stacks with charged nanopores were constructed and the ion current rectification phenomenon was observed. The trapping behavior of cations and anions in the nanochannels was found to be optimal at a specific electric field. The underlying mechanism of the rectification effect was elucidated based on the dependence between ion current and carrier concentration.
MATERIALS TODAY CHEMISTRY
(2023)
Article
Physics, Multidisciplinary
D. A. Bandurin, A. Principi, I. Y. Phinney, T. Taniguchi, K. Watanabe, P. Jarillo-Herrero
Summary: This study demonstrates that small-angle twisted bilayer graphene provides a highly tunable system for exploring interactions-limited electron conduction. Through the development of e-h drag theory, we reveal strong mutual friction between electrons and holes and clarify the conduction mechanisms in charge-neutral SATBG.
PHYSICAL REVIEW LETTERS
(2022)
Article
Materials Science, Multidisciplinary
Sanghyun Park, Seungchan Woo, Hongki Min
Article
Materials Science, Multidisciplinary
Jiho Jang, Seongjin Ahn, Hongki Min
Article
Physics, Multidisciplinary
SangEun Han, Changhee Lee, Eun-Gook Moon, Hongki Min
PHYSICAL REVIEW LETTERS
(2019)
Correction
Materials Science, Multidisciplinary
Sanghyun Park, Seungchan Woo, Hongki Min
Article
Physics, Multidisciplinary
Vo Tien Phong, Zachariah Addison, Seongjin Ahn, Hongki Min, Ritesh Agarwal, E. J. Mele
PHYSICAL REVIEW LETTERS
(2019)
Article
Chemistry, Physical
Hyeokshin Kwon, Taehwan Jeong, Samudrala Appalakondaiah, Youngtek Oh, Insu Jeon, Hongki Min, Seongjun Park, Young Jae Song, Euyheon Hwang, Sungwoo Hwang
Article
Physics, Multidisciplinary
Jeonghyeon Suh, Sanghyun Park, Hongki Min
Summary: Understanding the transport behavior of an electronic system under the influence of a magnetic field is crucial in condensed matter physics, especially in topological materials. The study focuses on the Boltzmann magnetotransport theory in topological materials with a nonvanishing Berry curvature, taking into account both the field-driven anisotropy and inherent anisotropy in the band dispersion. The results reveal the integral equation for the effective mean-free-path vector, considering the coupling between the magnetic field, Berry curvature, and mobility, and show the induced anisotropy in the relaxation time in Weyl semimetals.
NEW JOURNAL OF PHYSICS
(2023)
Article
Chemistry, Physical
Boogeon Choi, Gyouil Jeong, Seongjin Ahn, Hankyul Lee, Yunsu Jang, Baekwon Park, Hans A. Bechtel, Byung Hee Hong, Hongki Min, Zee Hwan Kim
Summary: We used IR-sSNOM to investigate SPPs in TLG and found systematic differences in near-field IR spectra and SPP wavelengths between Bernal (ABA) and rhombohedral (ABC) TLG domains on SiO2, which can be explained by stacking-dependent intraband conductivities. The reflection profiles of SPP at ABA-ABC boundaries can be largely explained by an idealized domain boundary defined by conductivity discontinuity. However, we observed distinct shapes in the SPP profiles at the edges of ABA and ABC TLG, which cannot be solely attributed to idealized edges with stacking-dependent conductivities. Instead, this can be explained by the presence of various edge structures with local conductivities differing from bulk TLGs.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Kyungjin Shin, Yunsu Jang, Jiseon Shin, Jeil Jung, Hongki Min
Summary: In this paper, we theoretically study the energy and optical absorption spectra of alternating-twist multilayer graphene (ATMG) under a perpendicular electric field. We analytically obtain the low-energy effective Hamiltonian of ATMG in the presence of interlayer bias and present general rules for constructing the effective Hamiltonian for any number of layers. Our results agree well with numerical calculations for large twist angles, and we also determine the tunable optical spectrum of ATMG.
Article
Materials Science, Multidisciplinary
Jeonghyeon Suh, Sunghoon Kim, E. H. Hwang, Hongki Min
Summary: We explicitly calculate the density-density response function with conserving vertex corrections for anisotropic multiband systems in the presence of impurities including long-range disorder. The direction dependence of the vertex corrections is correctly considered to obtain the diffusion constant which is given by a combination of componentwise transport relaxation times and velocities on the Fermi surface. We also investigate the diffusive density response of various anisotropic systems, propose some empirical rules for the corresponding diffusion constant, and demonstrate that it is crucial to consider the component dependence of the transport relaxation times to correctly interpret the transport properties of anisotropic systems, especially various topological materials with a different power-law dispersion in each direction.
Article
Materials Science, Multidisciplinary
Jiseon Shin, Bheema Lingam Chittari, Yunsu Jang, Hongki Min, Jeil Jung
Summary: In this study, we investigate the electronic structure of alternating-twist triple Bernal-stacked bilayer graphene (t3BG) by varying interlayer coupling, twist angle, interlayer potential difference, and sliding vector. We find that under certain parameters, the bands can flatten down to low energy levels, facilitating the formation of correlation-driven gaps.
Article
Materials Science, Multidisciplinary
Seungchan Woo, Brett Min, Hongki Min
Summary: This study reports the negative longitudinal magnetoresistance and angle-dependent planar Hall effect in topological semimetals and insulators due to Berry curvature. By utilizing the Boltzmann transport theory, the researchers present a closed-form expression for the nonequilibrium distribution function that incorporates both the effects of Berry curvature and Lorentz force. Based on this formulation, analytical expressions for conductivity and resistivity tensors in Weyl semimetals are obtained, demonstrating a characteristic field dependence resulting from the competition between the two effects.
Article
Materials Science, Multidisciplinary
Changhee Lee, Chiho Yoon, Taehyeok Kim, Suk Bum Chung, Hongki Min
Summary: We studied three-dimensional time-reversal-invariant topological superconductivity in noncentrosymmetric materials such as RhSi, CoSi, and AlPt, and found that a topological superconducting phase supporting a surface Majorana cone and topological nodal rings is favored in a wide range of interaction parameters in the tight-binding model for RhSi.
Article
Physics, Multidisciplinary
Sunghoon Kim, Hongki Min
PHYSICAL REVIEW RESEARCH
(2020)
Article
Materials Science, Multidisciplinary
Sunghoon Kim, Seungchan Woo, Hongki Min
