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1. Dirac Fermion Cloning, Moiré Flat Bands and Magic Lattice Constants in Epitaxial Monolayer Graphene

   https://doi.org/10.1002/adma.202200625  

   Lu, Qiangsheng; Le, Congcong; Zhang, Xiaoqian; Cook, Jacob; He, Xiaoqing; Zarenia, Mohammad; Vaninger, Mitchel; Miceli, Paul F.; Singh, David J.; Liu, Chang; et al (April 2022, Advanced Materials)

   Tuning interactions between Dirac states in graphene has attracted enormous interest because it can modify the electronic spectrum of the two-dimensional material, enhance electron correlations, and give rise to novel condensed-matter phases such as superconductors, Mott insulators, Wigner crystals and quantum anomalous Hall insulators. Previous works predominantly focus on the flat band dispersion of coupled Dirac states from different twisted graphene layers. In this work, we propose a new route to realizing flat band physics in monolayer graphene under a periodic modulation from substrates. We take graphene/SiC heterostructure as a prototypical example and demonstrate experimentally that the substrate modulation leads to Dirac fermion cloning and consequently, the proximity of the two Dirac cones of monolayer graphene in momentum space. Our theoretical modeling captures the cloning mechanism of Dirac states and indicates that Moiré flat bands can emerge at certain magic lattice constants of the substrate, specifically when the period of modulation becomes nearly commensurate with the (√3×√3)𝑅30∘ supercell of graphene. The results show that epitaxial single monolayer graphene on suitable substrates is a promising platform for exploring exotic many-body quantum phases arising from interactions between Dirac electrons. 

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2. Gate-tunable Veselago interference in a bipolar graphene microcavity

   https://doi.org/10.1038/s41467-022-34347-w  

   Zhang, Xi; Ren, Wei; Bell, Elliot; Zhu, Ziyan; Tsai, Kan-Ting; Luo, Yujie; Watanabe, Kenji; Taniguchi, Takashi; Kaxiras, Efthimios; Luskin, Mitchell; et al (December 2022, Nature Communications)

   Abstract The relativistic charge carriers in monolayer graphene can be manipulated in manners akin to conventional optics. Klein tunneling and Veselago lensing have been previously demonstrated in ballistic graphene pn-junction devices, but collimation and focusing efficiency remains relatively low, preventing realization of advanced quantum devices and controlled quantum interference. Here, we present a graphene microcavity defined by carefully-engineered local strain and electrostatic fields. Electrons are manipulated to form an interference path inside the cavity at zero magnetic field via consecutive Veselago refractions. The observation of unique Veselago interference peaks via transport measurement and their magnetic field dependence agrees with the theoretical expectation. We further utilize Veselago interference to demonstrate localization of uncollimated electrons and thus improvement in collimation efficiency. Our work sheds new light on relativistic single-particle physics and provide a new device concept toward next-generation quantum devices based on manipulation of ballistic electron trajectory. 

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3. Tunable interplay between light and heavy electrons in twisted trilayer graphene

   https://doi.org/10.1038/s41567-025-02956-z  

   Pierce, Andrew T; Xie, Yonglong; Park, Jeong Min; Cai, Zhuozhen; Watanabe, Kenji; Taniguchi, Takashi; Jarillo-Herrero, Pablo; Yacoby, Amir (August 2025, Nature Physics)

   In systems with multiple energy bands, the interplay between electrons with different effective masses drives correlated phenomena that do not occur in single-band systems. Magic-angle twisted trilayer graphene is a tunable platform for exploring such effects, hosting both heavy electrons in its flat bands and delocalized light Dirac electrons in dispersive bands. Superconductivity in this system spans a wider range of phase space than moiré materials without dispersive bands, suggesting that interband interactions influence the stabilization of correlated phases. Here we investigate the interplay between the light and heavy electrons in magic-angle twisted trilayer graphene by performing local compressibility measurements with a scanning single-electron-transistor microscope. We establish that weak incompressibility features near several integer moiré band fillings host a finite population of light Dirac electrons at the Fermi level, despite a gap opening in the flat band sector. At higher magnetic field near charge neutrality, we find a phase transition sequence that is robust over nearly 10 μm but exhibits complex spatial dependence. Calculations establish that the Dirac sector can be viewed as flavour analogous to the spin and valley degrees of freedom. 

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4. Engineering anisotropic electrodynamics at the graphene/CrSBr interface

   https://doi.org/10.1038/s41467-025-56804-y  

   Rizzo, Daniel J; Seewald, Eric; Zhao, Fangzhou; Cox, Jordan; Xie, Kaichen; Vitalone, Rocco A; Ruta, Francesco L; Chica, Daniel G; Shao, Yinming; Shabani, Sara; et al (December 2025, Nature Communications)

   Abstract Graphene is a privileged 2D platform for hosting confined light-matter excitations known as surface plasmon polaritons (SPPs), as it possesses low intrinsic losses and a high degree of optical confinement. However, the isotropic nature of graphene limits its ability to guide and focus SPPs, making it less suitable than anisotropic elliptical and hyperbolic materials for polaritonic lensing and canalization. Here, we present graphene/CrSBr as an engineered 2D interface that hosts highly anisotropic SPP propagation across mid-infrared and terahertz energies. Using scanning tunneling microscopy, scattering-type scanning near-field optical microscopy, and first-principles calculations, we demonstrate mutual doping in excess of 10¹³cm^–2holes/electrons between the interfacial layers of graphene/CrSBr. SPPs in graphene activated by charge transfer interact with charge-induced electronic anisotropy in the interfacial doped CrSBr, leading to preferential SPP propagation along the quasi-1D chains that compose each CrSBr layer. This multifaceted proximity effect both creates SPPs and endows them with anisotropic propagation lengths that differ by an order-of-magnitude between the in-plane crystallographic axes of CrSBr. 

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5. Restoration of weak localization in bilayer graphene by a molecular thin film

   https://doi.org/10.1088/2053-1583/ae4367  

   Mansour, Anise; Diaz, Deanna; Dissanayake_Mudiyanselage, Movindu_K D; Henkhaus, Erin; Cho, Jungyoun; Tran, Vinh; Ramirez, Francisco; Corona-Oceguera, Eric; Luna, Joshua; Kodama, Kenta; et al (February 2026, 2D Materials)

   Abstract Quantum coherent effects can be probed in multilayer graphene through electronic transport measurements at low temperatures. In particular, bilayer graphene (BLG) is known to be susceptible to quantum interference corrections of the conductivity, presenting weak localization at all electronic densities, and dependent on different scattering mechanisms such as those related to the trigonal warping of the electron dispersion near the K and K′ valleys. Proximity effects with a molecular thin film influence these scattering mechanisms, which can be quantified through the known theory of magnetoconductance for BLG. Here, we present electronic transport measurements in a copper-phthalocyanine (CuPc) / BLG / hexagonal boron nitride (h-BN) heterostructure that suggest the restoration of weak localization in BLG, associated to a reduction of trigonal warping effects, that are known to suppress weak localization in BLG. Additionally, we observe a charge transfer of 3.6×10¹²cm⁻²from the BLG to the molecules, as well as a very small degradation of the mobility of the BLG/h-BN heterostructure upon the deposition of CuPc. The molecular arrangement of the CuPc thin film is characterized in a control sample through transmission electron microscopy, that we relate to the electronic transport results. 

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