Synaptic computation, which is vital for information processing and decision making in neural networks, has remained technically challenging to be demonstrated without using numerous transistors and capacitors, though significant efforts have been made to emulate the biological synaptic transmission such as short-term and long-term plasticity and memory. Here, we report synaptic computation based on Joule heating and versatile doping induced metal-insulator transition in a scalable monolayer-molybdenum disulfide (MoS) device with a biologically comparable energy consumption (∼10 fJ). A circuit with our tunable excitatory and inhibitory synaptic devices demonstrates a key function for realizing the most precise temporal computation in the human brain, sound localization: detecting an interaural time difference by suppressing sound intensity- or frequency-dependent synaptic connectivity. This Letter opens a way to implement synaptic computing in neuromorphic applications, overcoming the limitation of scalability and power consumption in conventional CMOS-based neuromorphic devices.

The quantum confinement of charge carriers has been a promising approach to enhance the efficiency of thermoelectric devices, by lowering the dimension of materials and raising the boundary phonon scattering rate. The role of quantum confinement in thermoelectric efficiency has been investigated by using macroscopic device-scale measurements based on diffusive electron transport with the thermal de Broglie wavelength of the electrons. Here, we report a new class of thermoelectric operation originating from quasi-bound state electrons in low-dimensional materials. Coherent thermoelectric power from confined charges was observed at room temperature in graphene quantum dots with diameters of several nanometers. The graphene quantum dots, electrostatically defined as circular n–p–n junctions to isolate charges in the p-type graphene quantum dots, enabled thermoelectric microscopy at the atomic scale, revealing weakly localized and coherent thermoelectric power generation. The conceptual thermoelectric operation provides new insights, selectively enhancing coherent thermoelectric power via resonant states of charge carriers in low-dimensional materials.

Thermoelectricity has been investigated mostly on the macroscopic scale despite the fact that its origin is linked to the local electronic band structure of materials. While the role of thermopower from microscopic structures (e.g., surfaces or grain boundaries) increases for emerging thermoelectric materials, manipulating thermoelectric puddles, spatially varying levels of thermoelectric power on the nanometer scale, remains unexplored. Here, we illustrate thermoelectric puddles that can be harnessed via the stacking order and electronic screening in graphene. The local thermoelectric elements were investigated by gate-tunable scanning thermoelectric microscopy on the atomic scale, revealing the roles of local lattice symmetry, impurity charge scatterings, and mechanical strains in the thermopower system. The long-range screening of electrons at the Dirac point in graphene, which could be reached by in-operando spectroscopy, allowed us to unveil distinct thermoelectric puddles in the graphene that are susceptible to the stacking order and external strain. Thus, manipulating thermoelectric puddles via a lattice symmetry and electronic engineering will realize practical thermopower systems with low-dimensional materials.

Layered semimetals such as monoclinic MoTe2 and WTe2 demonstrate superconducting, topological insulating, and Weyl semimetallic states based on their unique electronic band topology. While doping concentration, lattice constants, and spin–orbit coupling can largely modulate the quantum states of the semimetals, a puzzling issue is that their functional carrier density and magnetoresistance for practical applications critically vary by temperature, which cannot be explained by the conventional phonon effect or a structural phase transition. Here, a native doping‐mediated thermomechanical manipulation of electric transport in semimetallic MoTe2 is reported, where effective transport is controlled by temperature in an equivalent manner to electric gating. Combining X‐ray diffraction, scanning tunneling microscopy, transport measurements, and first‐principles calculations, a Fermi level shift and subsequent changes in electronic structures are revealed as the origins of the practical transport changes in MoTe2. Moreover, the initial doping state of the MoTe2, determined by the Te vacancy density in two different growth methods, reciprocally affects the thermomechanical lattice and band structure changes, which is promising for novel electronic applications such as magnetic sensors and memory devices with layered semimetals.