Gate-Tunable Two-Dimensional Superlattices in Graphene

Abstract

We report an efficient technique to induce gatetunable two-dimensional superlattices in graphene by the combined action of a back gate and a few-layer graphene patterned bottom gate complementary to existing methods. The patterned gates in our approach can be easily fabricated and implemented in van der Waals stacking procedures, allowing flexible use of superlattices with arbitrary geometry. In transport measurements on a superlattice with a lattice constant a = 40 nm, wellpronounced satellite Dirac points and signatures of the Hofstadter butterfly including a nonmonotonic quantum Hall response are observed. Furthermore, the experimental results are accurately reproduced in transport simulations and show good agreement with features in the calculated band structure. Overall, we present a comprehensive picture of graphene-based superlattices, featuring a broad range of miniband effects, both in experiment and in theoretical modeling. The presented technique is suitable for studying more advanced geometries which are not accessible by other methods.

Valley Hall effect and nonlocal resistance in locally gapped graphene

“…Scattering-induced valley splitting, unlike Berry-phase induced deflection, is consistent with standard quantum transport methods, and provides an alternative mechanism to interpret valleytronic phenomena using R NL measurements. It also suggests a route towards valley engineering by using hBN or other substrates [50][51][52][53], patterned gates [54], or doping [55][56][57][58][59][60][61][62] to generate spatially varying mass profiles in graphene to direct the flow of valley currents.…”

Fermi Velocity Modulation Induced Low‐Bias Negative Differential Resistance in Graphene Double Barrier Resonant Tunneling diode

“…[ 1,4 ] In this regard, several reports demonstrated how the Fermi velocity alters graphene transport features [ 11–14 ] and its device performance. [ 15,16 ] Among graphene morphologies, quantum wells (QWs), [ 17,18 ] hetrostructures, [ 19–22 ] and superlattices (SLs) [ 23–26 ] have widely been implemented in designing/fabrication emerging devices [ 27–29 ] and exploring novel phenomenon [ 30–35 ] beyond the reach of exciting materials. In this context, resonant tunneling as one of the unique transport processes in SLs exhibited great promise to enrich the potential of SLs and QW devices including tunnel transistors (TFETs) [ 36–38 ] and resonant tunneling diodes (RTDs).…”

Brown-Zak and Weiss oscillations in a gate-tunable graphene superlattice: A unified picture of miniband conductivity

“…Artificial crystals, realised by moiré superlattices in heterostructures of 2D materials [1][2][3] or by imposing a nanopatterned superlattice [4][5][6] on a 2D electron system (2DES) like graphene, provide the opportunity to study transport characteristics of charge carriers in a periodic potential. Under the influence of such a superlattice it becomes possible to modify the band structure and therefore the electronic properties of 2D materials, leading, e.g., to the recent observation of superconductivity in magic-angle graphene [7].…”

“…The investigated graphene superlattice device with square lattice symmetry and lattice constant a = 39 nm was prepared following our previous works [6,18,24] (see Methods for more details). By combining one global back gate and a few-layer graphene patterned bottom gate (PBG) a periodic charge carrier density modulation is induced in monolayer graphene encapsulated between two hBN flakes and placed on top of the double gate structure (see inset in Fig.…”