The search for ever higher frequency information processing has become an area of intense research activity within the micro, nano, and optoelectronics communities. Compared to conventional ...semiconductor‐based diffusive transport electron devices, electron tunneling devices provide significantly faster response times due to near‐instantaneous tunneling that occurs at sub‐femtosecond timescales. As a result, the enhanced performance of electron tunneling devices is demonstrated, time and again, to reimagine a wide variety of traditional electronic devices with a variety of new “lightwave electronics” emerging, each capable of reducing the electron transport channel transit time down to attosecond timescales. In response to unprecedented rapid progress within this field, here the current state‐of‐the‐art in electron tunneling devices is reviewed, current challenges and opportunities are highlighted, and possible future research directions are identified.
Ultrafast electron tunneling devices are summarized. Compared to conventional semiconductor‐based electron transport devices, electron tunneling devices can provide, significantly, much faster response time due to near‐instantaneous tunneling that occurs on femtosecond timescales. The central tenet of optical‐field‐driven tunneling devices is realizing sub‐optical‐cycle response lightwave electronics.
Moiréless correlations in ABCA graphene Kerelsky, Alexander; Rubio-Verdú, Carmen; Xian, Lede ...
Proceedings of the National Academy of Sciences - PNAS,
01/2021, Letnik:
118, Številka:
4
Journal Article
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Atomically thin van der Waals materials stacked with an interlayer twist have proven to be an excellent platform toward achieving gate-tunable correlated phenomena linked to the formation of flat ...electronic bands. In this work we demonstrate the formation of emergent correlated phases in multilayer rhombohedral graphene--a simple material that also exhibits a flat electronic band edge but without the need of having a moiré superlattice induced by twisted van der Waals layers. We show that two layers of bilayer graphene that are twisted by an arbitrary tiny angle host large (micrometer-scale) regions of uniform rhombohedral four-layer (ABCA) graphene that can be independently studied. Scanning tunneling spectroscopy reveals that ABCA graphene hosts an unprecedentedly sharp van Hove singularity of 3-5-meV half-width. We demonstrate that when this van Hove singularity straddles the Fermi level, a correlated many-body gap emerges with peak-to-peak value of 9.5 meV at charge neutrality. Mean-field theoretical calculations for model with short-ranged interactions indicate that two primary candidates for the appearance of this broken symmetry state are a charge-transfer excitonic insulator and a ferrimagnet. Finally, we show that ABCA graphene hosts surface topological helical edge states at natural interfaces with ABAB graphene which can be turned on and off with gate voltage, implying that small-angle twisted double-bilayer graphene is an ideal programmable topological quantum material.
Metalloproteins, proteins containing a transition metal ion cofactor, are electron transfer agents that perform key functions in cells. Inspired by this fact, electron transport across these proteins ...has been widely studied in solid-state settings, triggering the interest in examining potential use of proteins as building blocks in bioelectronic devices. Here, we report results of low-temperature (10 K) electron transport measurements via monolayer junctions based on the blue copper protein azurin (Az), which strongly suggest quantum tunneling of electrons as the dominant charge transport mechanism. Specifically, we show that, weakening the protein–electrode coupling by introducing a spacer, one can switch the electron transport from off-resonant to resonant tunneling. This is a consequence of reducing the electrode’s perturbation of the Cu(II)-localized electronic state, a pattern that has not been observed before in protein-based junctions. Moreover, we identify vibronic features of the Cu(II) coordination sphere in transport characteristics that show directly the active role of the metal ion in resonance tunneling. Our results illustrate how quantum mechanical effects may dominate electron transport via protein-based junctions.
A physics-based model for the tunneling current of vertical tunneling field transistors (TFET) is proposed. In part I, the expression of <inline-formula> <tex-math notation="LaTeX">\varphi _{\text ...{1D}}{(}\textit {x}{)} </tex-math></inline-formula> is derived from the multi-branch general solutions of Poisson's equation. The model's results are verified with TCAD simulation for transistors with different materials, device geometries, and biases. In this article, a surface potential model is validated at different device regions which include channel and drain. Based on the above two electric potential models, Kane's tunneling formula is utilized for the calculation of band-to-band tunneling current. The proposed current model is valid for all transistors' operating regions. The quantum effect on the band-structure parameters is taken into account in the modeling of InAs vertical TFET. It is shown that the channel thickness needs to be optimized to achieve the highest drive current.
Triangular zigzag nanographenes, such as triangulene and its π‐extended homologues, have received widespread attention as organic nanomagnets for molecular spintronics, and may serve as building ...blocks for high‐spin networks with long‐range magnetic order, which are of immense fundamental and technological relevance. As a first step towards these lines, we present the on‐surface synthesis and a proof‐of‐principle experimental study of magnetism in covalently bonded triangulene dimers. On‐surface reactions of rationally designed precursor molecules on Au(111) lead to the selective formation of triangulene dimers in which the triangulene units are either directly connected through their minority sublattice atoms, or are separated via a 1,4‐phenylene spacer. The chemical structures of the dimers have been characterized by bond‐resolved scanning tunneling microscopy. Scanning tunneling spectroscopy and inelastic electron tunneling spectroscopy measurements reveal collective singlet–triplet spin excitations in the dimers, demonstrating efficient intertriangulene magnetic coupling.
The on‐surface synthesis of covalently bonded triangulene dimers with or without a 1,4‐phenylene spacer was achieved on Au(111). Scanning tunneling spectroscopy measurements revealed collective magnetism in the dimers in the form of singlet–triplet spin excitations, demonstrating efficient and tunable intertriangulene magnetic coupling.
Relations for the optimum well width, barrier width, and width of the spacer layer which correspond to the highest PVCR based on effective mass and barrier height in RTDs are proposed. The optimum ...spacer layer is found to be half of the de-Broglie wavelength associated with the bound state of the corresponding finite quantum well. The proposed relations for the optimum parameters can be used to design RTD based on any two appropriate materials to attain the highest PVCR. The effect of doping concentrations on PVCR and peak current was studied. As a case study, we have considered the GaAs/Ga0.7Al0·3As, GaN/Ga0.7Al0·3N, and In0.53Ga0.47 As/AlAs RTDs. The transfer matrix formalism is extended to study the current-voltage relation in polar GaN/AlN RTDs.
•Optimum device parameters to obtain maximum PVCR were proposed.•Relations between optimum spacer layer width and De Broglie wavelength corresponding to the bound state of respective finite quantum well were obtained.•Dependence of well and barrier widths on effective masses of electrons in well and barrier materials were demonstrated.
It is well known that resonant tunneling can significantly increase the tunneling current when the incident particle's energy (Ω) is equal to the resonant energy (ΩR). However, recent studies have ...shown that complex current structures can emerge when the resonant energy varies in time. While these temporal variations typically increase the current, there is a specific condition under which the current is significantly suppressed. This condition, which has previously only been presented for specific cases, is characterized by the equation
12∫t1t1|Ω−ΩR(t′)|dt′=π(n−14) for =1,2,... , where t1,2 are the solutions of ΩR(t1,2)=Ω.
In this paper, we present for the first time a full derivation of this expression using the Quasi-Bound Super State method and demonstrate it for various perturbation scenarios with the following temporal profiles: Gaussian, hyperbolic secant, harmonic, and smooth rectangular.
The derivation of this quantization rule has practical implications beyond the intellectual realm. The specific spectral structure of these systems has implications for nanotechnology (e.g., frequency-controlled transistors) and the understanding of biological and biochemical processes (e.g., odor detection).
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