Probing interlayer electronic interaction via Coulomb drag in hybrid dimensional system and band-to-band-tunneling in vertical heterostructures of two-dimensional material
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Abstract:
Over the years the search for realizing highly correlated states has led to the discovery of novel many-body states like excitonic condensate states, fractional quantum hall states [1], Luttinger liquid phase etc. Over the last two-decades, extensive research on graphene and other two-dimensional layered material has led to remarkable improvement in the device quality and architecture. Especially, the realization of stacking multiple layered materials has been the core of realizing such correlated phases in condensed matter systems.
In my talk, I will present results of Coulomb drag measurement between a one-dimensional InAs nanowire (NW) and two-dimensional graphene systems [2]. Coulomb drag which arises due to interlayer momentum and energy transfer is the measure of the interlayer electron-electron interaction. For monolayer graphene (MLG)-NW heterostructures, we observe an unconventional drag resistance peak near the Dirac point due to the correlated interlayer charge puddles. The drag signal shows unconventional behaviour with temperature (~?−2), carrier density of nanowire (~??−4), and magnetic field (~?2). These anomalous responses, together with the mismatched thermal conductivities of graphene and NWs, establish the Energy drag as the responsible mechanism of Coulomb drag in MLG-NW devices. In contrast, for bilayer graphene (BLG)-NW devices the drag resistance reverses sign across the Dirac point and the magnitude of the drag signal decreases with the carrier density of the NW (~??−1.5), consistent with the momentum drag but remains almost constant with magnetic field and temperature.
In the second part of my talk, I will discuss band-to-band-tunnelling (BTBT) observed in dual-gated vertical heterostructures of few-layers of MoTe2 and SnS2 which has natural broken or type III band alignment [3]. We report observation of negative differential resistance (NDR) signal for the first time in our heterostructures which arises due to type III band alignment. We achieve significant gate tunability of the NDR signal with peak-to-valley ratio (PVR) of ~3 for a gate voltage range down to 50K. Such gate controllability of NDR is rare in van der Waals materials due to the limitation of high intrinsic doping and low penetration depth of gate electric field and has great potential as application in reconfigurable circuit and logic devices.
References:
[1] Eisenstein, J. P., et al. "New fractional quantum Hall state in double-layer two-dimensional electron systems." Physical review letters 68.9 (1992): 1383.
[2] Mitra, Richa, et al. "Anomalous Coulomb drag between InAs nanowire and graphene heterostructures." Physical Review Letters 124.11 (2020): 116803.
[3] Iordanidou, Konstantina, et al. "Electric Field and Strain Tuning of 2D Semiconductor van der Waals Heterostructures for Tunnel Field-Effect Transistors." ACS Applied Materials & Interfaces (2022).