arXiv subjects

Evgenii E. Vdovin

Publications and source records attributed to Evgenii E. Vdovin.

4 recordsLinked to original sources

arXiv2026

Tunneling characteristics of twisted double bilayer graphene heterostructures

Electron tunneling between sheets of bilayer Bernal graphene twisted at different small angles was studied experimentally and theoretically. The current-voltage characteristics exhibit resonant peaks, steps, and regions of negative differential resistance, the origin of which is explained by the intersections of energy- and momentum-shifted electron dispersions of adjacent layers. A theoretical analysis of tunneling transport demonstrated that the key to understanding this phenomenon lies in the competition between two contributions: between like (conductivity-conductivity or valence-valence) and unlike (conductivity-valence) bands of parallel bilayer graphene sheets. A systematic evolution of the tunneling current patterns with increase of the twist angle is investigated. Polarization of electron wave function across graphene sublayers caused by displacement field within bilayer graphene is shown to strongly affect the tunneling probability, thus enhancing negative differential resistance due to Van Hove singularities at the band edges.

cond-mat.mes-hall↗

arXiv2025

Probing the features of electron dispersion by tunneling between slightly twisted bilayer graphene sheets

Tunneling conductance between two bilayer graphene (BLG) sheets separated by 2 nm-thick insulating barrier was measured in two devices with the twist angles between BLGs less than 1°. At small bias voltages, the tunneling occurs with conservation of energy and momentum at the points of intersection between two relatively shifted Fermi circles. Here, we experimentally found and theoretically described signatures of electron-hole asymmetric band structure of BLG: since holes are heavier, the tunneling conductance is enhanced at the hole doping due to the higher density of states. Another key feature of BLG that we explore is gap opening in a vertical electric field with a strong polarization of electron wave function at van Hove singularities near the gap edges. This polarization, by shifting electron wave function in one BLG closer to or father from the other BLG, gives rise to asymmetric tunneling resonances in the conductance around charge neutrality points, which result in strong sensitivity of the tunneling current to minor changes of the gate voltages. The observed phenomena are reproduced by our theoretical model taking into account electrostatics of the dual-gated structure, quantum capacitance effects, and self-consistent gap openings in both BLGs.

cond-mat.mes-hall↗

arXiv2023

Infrared photodetection in graphene-based heterostructures: bolometric and thermoelectric effects at the tunneling barrier

Graphene/hBN/graphene tunnel devices offer promise as sensitive mid-infrared photodetectors but the microscopic origin underlying the photoresponse in them remains elusive. In this work, we investigated the photocurrent generation in graphene/hBN/graphene tunnel structures with localized defect states under mid-IR illumination. We demonstrate that the photocurrent in these devices is proportional to the second derivative of the tunnel current with respect to the bias voltage, peaking during tunneling through the hBN impurity level. We revealed that the origin of the photocurrent generation lies in the change of the tunneling probability upon radiation-induced electron heating in graphene layers, in agreement with the theoretical model that we developed. Finally, we show that at a finite bias voltage, the photocurrent is proportional to the either of the graphene layers heating under the illumination, while at zero bias, it is proportional to the heating difference. Thus, the photocurrent in such devices can be used for accurate measurements of the electronic temperature providing a convenient alternative to Johnson noise thermometry.

cond-mat.mes-hall↗

arXiv2021

Twisted monolayer and bilayer graphene for vertical tunneling transistors

We prepare twist-controlled resonant tunneling transistors consisting of monolayer (Gr) and Bernal bilayer (BGr) graphene electrodes separated by a thin layer of hexagonal boron nitride (hBN). The resonant conditions are achieved by closely aligning the crystallographic orientation of the graphene electrodes, which leads to momentum conservation for tunneling electrons at certain bias voltages. Under such conditions, negative differential conductance (NDC) can be achieved. Application of in-plane magnetic field leads to electrons acquiring additional momentum during the tunneling process, which allows control over the resonant conditions.

cond-mat.mes-hall↗