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Electronics and photonics research at Pohang University of Science and Technology (POSTECH) spans from metasurface flat optical devices to quantum and stretchable electronics. In this Viewpoint, five professors discuss how POSTECH, with strong industry ties and interdisciplinary collaborations, aims to redefine nanoscale electronic and photonic materials and devices, quantum electronics and photonics, future information technology and computing.

The standard topological insulator is characterized by an insulating bulk and a conducting boundary, so a three dimensional insulating bulk of a topological insulator has a conducting surface. Recently, this idea was extended to the edges of the surfaces of the three dimensional material as a new topological phase, referred to as a higher-order topological insulator. Here, the authors find evidence of such higher order topological insulator states in tungsten ditelluride using heterostructures composed of tungsten ditelluride and graphene.

The valley Hall effect in 2D materials is a promising approach for future valleytronic applications, but it is usually based on excitons with short lifetimes. Here, spin polarized electrons are injected from WTe₂ into MoS₂, leading to a unipolar valley Hall effect with enhanced lifetimes and mobility.

The optical Stark effect is a light-matter interaction phenomenon that can be used to address and control exciton states in semiconductors. Here, the authors achieve optical tuning of the Stark effect of an individual exciton state in few-layer ReS₂with varying light polarization.

Single atomic layers of transition metal dichalcogenides have outstanding electrical and optical properties. Here, the authors show that light absorption and emission from stacks of different transition metal dichalcogenide monolayers can be tuned by rotating the crystals.

The improvement of the thermoelectric figure of merit ZT has been hindered by the challenges associated with the independent control of the electrical and thermal conductivity. Here the authors show that SnS₂nanosheets can lead to an increased ZT via negative correlation between electrical and thermal conductivity.

Few-layer molybdenum ditelluride and tungsten diselenide field-effect transistors can be reversibly doped with different carrier types and concentrations using pulses of ultraviolet and visible light, allowing reconfigurable complementary metal–oxide–semiconductor circuits to be created.

A laser can be used to locally dope two-dimensional molybdenum ditelluride channels, allowing both n- and p-doped channels to be assembled within the same atomic plane and for device arrays of n–p–n bipolar junction transistor amplifiers and radial p–n photovoltaic cells to be fabricated.

We demonstrate a single-domain photovoltaic switch based on lateral BiFeO₃ channels, in which such photovoltaic switching is achieved by a coherent single-domain reversal with a short electrical pulse. We then provide visual evidence for such operations with a series of spatially and spectrally resolved short circuit photocurrent images. Specifically, it reveals that the sequential photovoltaic current images directly reflect the remanent polarization states of a single-domain channel. We also verify that, in multidomain channels, the diffusive switching characteristics is determined not only by the internal polarization vector within the domain but also by oxygen vacancy migration at the domain walls.

The authors study the light-driven dynamics of attractive and repulsive Fermi polarons in monolayer WSe₂. They show that the resonance shifts of Fermi polarons are valley-selective; the resonance shifts of attractive polarons increase with Fermi-sea density, while those of repulsive polarons decrease.

Plasmonics is heralded as the perfect symbiosis of optics, which is quick, and electronics, which works on a small scale. A method for electrically detecting plasmon polaritons using a quantum dot removes the need for far-field optical techniques and could enable nanoscale integrated circuits.

Lateral TMD–graphene–topological insulator hetero-devices enable room-temperature optoelectronic transport of the valley-locked spin polarization degree of freedom.

Mirror twin boundaries in monolayer MoS₂—line defects with reflection-mirroring symmetry—are one-dimensionally metallic. In this work, the authors fabricate these mirror twin boundary networks by epitaxity and incorporate them into ultrascaled 2D transistor circuits as gate electrodes.

Correlated insulator states of moire excitons in transition metal dichalcogenide heterostructures have attracted significant attention recently. Here the authors use time-resolved pump-probe spectroscopy to demonstrate the effects of non-equilibrium correlations of moire excitons in WSe₂/WS₂ heterobilayers.

Under strong laser fields, materials exhibit extreme non-linear optical response, such as high harmonic generation. These higher harmonics provide insights into electron behaviour in materials in sub-laser cycle timescale. Here, Cha et al study higher harmonic generation resulting from the laser driven motion of massless Dirac fermions in graphene.

Geometric confinement on arbitrary substrates promotes, without epitaxial seeding, the layer-by-layer growth of two-dimensional single-crystal monolayers and bilayers of transition metal dichalcogenides.

Excitons—bound electron-hole pairs—in two-dimensional transition-metal dichalcogenides can exhibit a rich spectrum of excited states. Here, the authors use ultrafast mid-infrared spectroscopy to explore the dynamics of these so-called 1s-intraexcitonic transitions in monolayer molybdenum disulphide.

For optical control of plasmons metals require a large amount of power in the control pulse, yielding a small modulation depth. Here, Sim et al. fabricate arrays of Bi₂Se₃ and report a modulation depth of 2,400% at 1.5 THz with an optical fluence of 45 μJ/cm², demonstrating a novel route for controlling plasmons.

Here, the authors report the observation of deep-ultraviolet (DUV) electroluminescence and photocurrent generation in van der Waals heterostructures based on hBN crystals, showing potential for DUV light emitting and detection devices.

Kinetics-controlled van der Waals epitaxy in the near-equilibrium limit by metal–organic chemical vapour deposition enables precise layer-by-layer stacking of dissimilar transition metal dichalcogenides.

Quantum beats are periodic oscillations originating from the superposition of coherent quantum states. Here, the authors observe exciton quantum beats in the optical spectrum of atomically thin ReS₂, and modulate the intensity of the quantum beat signal by means of light polarisation.

The photocurrent in polymorphic phase areas of BiFeO₃ is enhanced by a factor of 100 due to interfacial strain gradients across the different structural phases.

Sequential heteroepitaxy of transition-metal dichalcogenide polymorphs with different electronic properties is used to build coplanar ultrathin circuitry with atomic-scale precision.

We provide a conclusive demonstration of strain-induced room-temperature ferroelectricity in SrMnO₃ thin films by securing samples with insulating properties and clean surfaces using selective oxygen annealing. These findings will not only provide a cornerstone for exploring the physical properties of multiferroic SrMnO₃ but will also inspire new directions for single-phase multiferroics.