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Bi2Te3‐based materials are not only the most important and widely used room temperature thermoelectric (TE) materials but are also canonical examples of topological insulators in which the topological surface states are protected by the time‐reversal symmetry. High‐performance thin films based on Bi2Te3 have attracted worldwide attention during the past two decades due primarily to their outstanding TE performance as highly efficient TE coolers and as miniature and flexible TE power generators for a variety of electronic devices. Moreover, intriguing topological phenomena, such as the quantum anomalous Hall effect and topological superconductivity discovered in Bi2Te3‐based thin films and heterostructures, have shaped research directions in the field of condensed matter physics. In Bi2Te3‐based films and heterostructures, delicate control of the carrier transport, film composition, and microstructure are prerequisites for successful device operations as well as for experimental verification of exotic topological phenomena. This review summarizes the recent progress made in atomic defect engineering, carrier tuning, and band engineering down to a nanoscale regime and how it relates to the growth and fabrication of high‐quality Bi2Te3‐based films. The review also briefly discusses the physical insight into the exciting field of topological phenomena that were so dramatically realized in Bi2Te3‐ and Bi2Se3‐based structures. It is expected that Bi2Te3‐based thin films and heterostructures will play an ever more prominent role as flexible TE devices collecting and converting low‐level (body) heat into electricity for numerous electronic applications. It is also likely that such films will continue to be a remarkable platform for the realization of novel topological phenomena. Bi2Te3‐based materials are one type of the most popular thermoelectric materials and topological insulators, whereby their thin films are particularly suitable for important applications in the efficient active cooling and self‐powered power supply for miniaturized/flexible electronic devices as well as in the low power electronics and quantum computation. Tremendous efforts regarding the delicate control of the atomic point defects, chemical composition, preferential orientation, magnetic doping, and also spin‐orbit coupling have been exerted for the optimization of electronic band structure, topological surface states, electrical and thermal transport, and topological electronic transport of Bi2Te3‐based thin films, and hence for the proof‐of‐principle demonstration and practical applications of Bi2Te3‐based thin film devices. It is widely accepted that Bi2Te3‐based thin films will be of great significance for thin‐film thermoelectric applications and for discovering novel topological phenomena and relevant applications in the near future.

Magnetic properties of materials ranging from conventional ferromagnetic metals to strongly correlated materials such as cuprates originate from Coulomb exchange interactions. The existence of alternate mechanisms for magnetism that could naturally facilitate electrical control has been discussed theoretically 1 – 7 , but an experimental demonstration 8 in an extended system has been missing. Here we investigate MoSe 2 /WS 2 van der Waals heterostructures in the vicinity of Mott insulator states of electrons forming a frustrated triangular lattice and observe direct evidence of magnetic correlations originating from a kinetic mechanism. By directly measuring electronic magnetization through the strength of the polarization-selective attractive polaron resonance 9 , 10 , we find that when the Mott state is electron-doped, the system exhibits ferromagnetic correlations in agreement with the Nagaoka mechanism. Minimization of kinetic energy leads to ferromagnetic correlations between itinerant electrons in MoSe 2 /WS 2 moiré lattices even in the absence of exchange interactions.

Molecular electronics that can produce functional electronic circuits using a single molecule or molecular ensemble remains an attractive research field because it not only represents an essential step toward realizing ultimate electronic device scaling but may also expand our understanding of the intrinsic quantum transports at the molecular level. Recently, in order to overcome the difficulties inherent in the conventional approach to studying molecular electronics and developing functional device applications, this field has attempted to diversify the electrical characteristics and device architectures using various types of heterogeneous structures in molecular junctions. This review summarizes recent efforts devoted to functional devices with molecular heterostructures. Diverse molecules and materials can be combined and incorporated in such two‐ and three‐terminal heterojunction structures, to achieve desirable electronic functionalities. The heterojunction structures, charge transport mechanisms, and possible strategies for implementing electronic functions using various hetero unit materials are presented sequentially. In addition, the applicability and merits of molecular heterojunction structures, as well as the anticipated challenges associated with their implementation in device applications are discussed and summarized. This review will contribute to a deeper understanding of charge transport through molecular heterojunction, and it may pave the way toward desirable electronic functionalities in molecular electronics applications. The authors present recent advances to develop a wide spectrum of molecular heterostructures, as well as their prospects and applicability. Various molecular heterostructures and their novel electrical characteristics, along with their charge transport mechanisms are presented. In addition, the potential applicability, merits, and perspectives, as well as the anticipated challenges associated with their implementation in electronic device applications are discussed.

Accurate values for polarization discontinuities between pyroelectric materials are critical for understanding and designing the electronic properties of heterostructures. For wurtzite materials, the zincblende structure has been used in the literature as a reference to determine the effective spontaneous polarization constants. We show that, because the zincblende structure has a nonzero formal polarization, this method results in a spurious contribution to the spontaneous polarization differences between materials. In addition, we address the correct choice of “improper” versus “proper” piezoelectric constants. For the technologically important III-nitride materials GaN, AlN, and InN, we determine polarization discontinuities using a consistent reference based on the layered hexagonal structure and the correct choice of piezoelectric constants, and discuss the results in light of available experimental data.

Van der Waals (vdW) heterostructures provide a unique opportunity to develop various electronic and optoelectronic devices with specific functions by designing novel device structures, especially for bioinspired neuromorphic optoelectronic devices, which require the integration of nonvolatile memory and excellent optical responses. Here, we demonstrate a programmable optoelectronic synaptic floating‐gate transistor based on multilayer graphene/h‐BN/MoS2 vdW heterostructures, where both plasticity emulation and modulation were successfully realized in a single device. The dynamic tunneling process of photogenerated carriers through the as‐fabricated vdW heterostructures contributed to a large memory ratio (105) between program and erase states. Our device can work as a functional or silent synapse by applying a program/erase voltage spike as a modulatory signal to determine the response to light stimulation, leading to a programmable operation in optoelectronic synaptic transistors. Moreover, an ultra‐low energy consumption per light spike event (~2.5 fJ) was obtained in the program state owing to a suppressed noise current by program operation in our floating‐gate transistor. This study proposes a feasible strategy to improve the functions of optoelectronic synaptic devices with ultra‐low energy consumption based on vdW heterostructures designed for highly efficient artificial neural networks. A neuromorphic optoelectronic floating‐gate transistor based on multilayer graphene/h‐BN/MoS2 vdW heterostructure exhibits programmable synaptic plasticity due to the unique light‐induced carrier tunneling through vdW heterostructure. Ultra‐low energy consumption for the electrical response to light stimulation is also realized under a low Vds at program state, demonstrating its great potential in building efficient artificial neural networks based on vdW heterostructures.

Timely and accurately identification of the novel coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection can greatly contribute to monitoring and controlling the global pandemic. This study gained theoretical insight into a novel phase-modulation plasmonic biosensor working in the near-infrared (NIR) regime, which can be employed for sensitive detection of SARS-CoV-2 and its spike (S) glycoprotein. The proposed plasmonic biosensor was created by integrating two-dimensional (2D) Van der Waals heterostructures, including tellurene and carboxyl-functionalized molybdenum disulfide (MoS2) layers, with transparent indium tin oxide (ITO) film. Excellent biosensing performance can be achieved under the excitation of 1550 nm by optimizing the thickness of ITO film and tellurene-MoS2 heterostructures. For a sensing interface refractive index change as low as 0.0012 RIU (RIU, refractive index unit), the optimized plasmonic configuration of 121 nm ITO film/three-layer tellurene/ten-layer MoS2-COOH can produce the highest detection sensitivity of 8.4069 × 104 degree/RIU. More importantly, MoS2-COOH layer can capture angiotensin-converting enzyme II, which is an ideal adsorption site for specifically binding SARS-CoV-2 S glycoprotein. Then, an excellent linear detection range for S glycoprotein and SARS-CoV-2 specimens is ∼0-301.67 nM and ∼0-67.8762 nM, respectively. This study thus offers an alternative strategy for rapidly performing novel coronavirus diagnosis in clinical applications.

One of the promising platforms for creating Majorana bound states is a hybrid nanostructure consisting of a semiconducting nanowire covered by a superconductor. We analyze the previously disregarded role of electrostatic interaction in these devices. Our main result is that Coulomb interaction causes the chemical potential to respond to an applied magnetic field, while spin-orbit interaction and screening by the superconducting lead suppress this response. Consequently, the electrostatic environment influences two properties of Majorana devices: the shape of the topological phase boundary and the oscillations of the Majorana splitting energy. We demonstrate that both properties show a non-universal behavior, and depend on the details of the electrostatic environment. We show that when the wire only contains a single electron mode, the experimentally accessible inverse self-capacitance of this mode fully captures the interplay between electrostatics and Zeeman field. This offers a way to compare theoretical predictions with experiments.

Moiré superlattices in van der Waals heterostructures have emerged as a powerful tool for engineering quantum phenomena. Here we report the observation of a correlated interlayer exciton insulator in a double-layer heterostructure composed of a WSe 2 monolayer and a WS 2 /WSe 2 moiré bilayer that are separated by ultrathin hexagonal boron nitride. The moiré WS 2 /WSe 2 bilayer features a Mott insulator state when the density of holes is one per moiré lattice site. When electrons are added to the Mott insulator in the WS 2 /WSe 2 moiré bilayer and an equal number of holes are injected into the WSe 2 monolayer, a new interlayer exciton insulator emerges with the holes in the WSe 2 monolayer and the electrons in the doped Mott insulator bound together through interlayer Coulomb interactions. The interlayer exciton insulator is stable up to a critical hole density in the WSe 2 monolayer, beyond which the interlayer exciton dissociates. Our study highlights the opportunities for realizing quantum phases in double-layer moiré systems due to the interplay between the moiré flat band and strong interlayer electron interactions. When independent layers of electrons and holes are in close proximity to each other, their Coulomb interaction allows them to pair into neutral bosons and form an insulating state. This phenomenon is reported in a heterostructure of 2D materials.

We present results of a comprehensive investigation of two phenomena arising in superconductor(S)/ferromagnet(F) heterostructures of Nb on FePd with a lateral magnetic domain pattern: domain-superconductivity and spin-triplet Cooper pair generation. Resistivity measurements in a magnetic field applied out-of-plane to a Nb/FePd (S/F) sample with high magnetocrystalline anisotropy give evidence of stray field generated domain-wall- and reverse-domain-superconductivity. A corresponding bilayer comprising low magnetocrystalline anisotropy exhibits spin-triplet Cooper pair generation and a notable high variation of the S critical temperature due to spin-triplet generation (ΔTc) of 100 mK in an in-plane applied field. Using reference samples we can clearly distinguish stray field from proximity effects. The relevance of the characteristic S and F length scales related to the observed proximity effects is discussed.