Moiré Superlattices and Band Engineering
By stacking atomically thin layers at a controlled twist angle, we engineer electronic band structures that are impossible in any single material. Our work in bilayer graphene/hBN moiré superlattices has uncovered a hierarchy of miniband gaps, emergent Dirac fermions, and new mechanisms for controlling electron-electron interactions — all with simple electrostatic gates.
Some representative results are mentioned below:
Quantum transport spectroscopy of pseudomagnetic field in graphene Phys. Rev. Lett. (2026)
Non-uniform strain in graphene generates a pseudomagnetic field that acts on electrons like a real magnetic field but preserves time-reversal symmetry. While such fields have previously been visualised only by local probes, we demonstrate that high-mobility graphene exhibits distinct beating patterns in Shubnikov-de Haas oscillations arising from valley-resolved Landau quantization under different effective magnetic fields. Systematic analysis of the beating nodes reveals universal quadratic and linear scaling with applied magnetic field, enabling extraction of pseudomagnetic fields as small as a few millitesla. Our results establish quantum oscillation spectroscopy as a robust macroscopic transport probe of strain-induced gauge fields in Dirac materials, opening avenues for mechanically tunable valleytronic and straintronic devices.
D. Sahani, S. Das, K. Watanabe, T. Taniguchi, A. Agarwal, Aveek Bid — Phys. Rev. Lett. 136, 166604 (2026) | arXiv:2511.14888
Coexisting massive and massless Dirac fermions in moiré-reconstructed bilayer graphene Phys. Rev. B (2026)
Moiré superlattices formed between bilayer graphene and hexagonal boron nitride are known to host a rich set of satellite Dirac points at the superlattice Brillouin zone boundaries. We demonstrate that hBN alignment induces a topological band reconstruction in bilayer graphene superlattices, generating secondary bands that host massless, chiral fermions while the primary band retains its massive chiral character. Magnetotransport measurements including quantum Hall, temperature-dependent Shubnikov-de Haas oscillations, and Berry phase analysis confirm the distinct topological nature of these bands. A significantly reduced Fermi velocity in the moiré secondary band indicates band flattening induced by the moiré potential.
M. K. Jat, K. Watanabe, T. Taniguchi, Aveek Bid — Phys. Rev. B 113, L081102 (2026) | arXiv:2510.20309
Higher-order gaps in the renormalized band structure of doubly aligned hBN/bilayer graphene moiré superlattice Nature Communications (2024)
When bilayer graphene is aligned with hBN on both sides, the two moiré superlattices interfere to produce a hierarchy of miniband gaps at wavevectors corresponding to higher-order umklapp processes. We observe these higher-order gaps in transport and show that their magnitude significantly exceeds predictions based on a bare moiré potential. This strong renormalization of the band structure arises from electron-electron interactions within the moiré flat bands, demonstrating that correlation effects are crucial for understanding the electronic structure of doubly aligned devices.
M. K. Jat, P. Tiwari, R. Bajaj, I. Shitut, S. Mandal, K. Watanabe, T. Taniguchi, H. R. Krishnamurthy, M. Jain, Aveek Bid — Nat. Commun. 15, 2335 (2024) | arXiv:2304.01720
Controlling Umklapp scattering in a bilayer graphene moiré superlattice Nano Letters (2024)
Umklapp scattering — where electrons scatter with a momentum transfer equal to a reciprocal lattice vector — is normally a fixed property of a crystal. In a moiré superlattice, the moiré reciprocal lattice vectors are tunable through twist angle and gating. We demonstrate gate-controlled Umklapp scattering in a bilayer graphene moiré device, showing that the strength of umklapp processes and the associated resistivity peak can be continuously tuned by a back-gate voltage. This provides a new, electrically controlled knob for engineering electron-electron interactions in moiré systems.
M. K. Jat, S. Mishra, H. K. Mann, R. Bajaj, K. Watanabe, T. Taniguchi, H. R. Krishnamurthy, M. Jain, Aveek Bid — Nano Lett. 24, 2203 (2024) | arXiv:2310.08906