Semiconductors

  • Article
    | Open Access

    Berghoff et al. discover that polycrystalline MAPbI3 undergoes transient Wannier Stark localization at moderate field strengths, exhibiting substantial optical modulation with a fast response time. Since the polycrystallinity does not hinder the switching behaviour, this low-cost material is promising for light modulation and photonic applications.

    • Daniel Berghoff
    • , Johannes Bühler
    •  & Heejae Kim
  • Article
    | Open Access

    Naturally occurring hyperbolic polaritons exist in a class of layered materials. Here, the authors show evidence, via optical spectroscopy, of hyperbolic exciton-polaritons in phosphorene, originating from its in-plane anisotropy and strong exciton resonances.

    • Fanjie Wang
    • , Chong Wang
    •  & Hugen Yan
  • Article
    | Open Access

    Point defects compromise the electronic performance of hybrid perovskites, yet no experimental identifications have been reported. Here, the authors, for the first time, identify lead monovacancy defect in MAPbI3 using positron annihilation lifetime spectroscopy with the aid of density functional theory.

    • David J. Keeble
    • , Julia Wiktor
    •  & Werner Egger
  • Article
    | Open Access

    Here, the authors report on evidence of an excitonic species formed by electrons in high-energy conduction band states with a negative effective mass, explaining previous observations of quantum interference phenomena in two-dimensional semiconductors.

    • Kai-Qiang Lin
    • , Chin Shen Ong
    •  & John M. Lupton
  • Article
    | Open Access

    Optical excitation of transition metal dichalcogenide monolayers mostly generates excitons species with inherently short lifetime and spin/valley relaxation time. Here, the authors demonstrate efficient spin/valley optical pumping of resident electrons in n-doped WSe2 and WS2 monolayers.

    • Cedric Robert
    • , Sangjun Park
    •  & Xavier Marie
  • Article
    | Open Access

    Room-temperature exciton polaritons in a monolayer WS2 are shown to display strong motional narrowing of the linewidth and enhanced first-order coherence. They can propagate for tens of micrometers while maintaining partial coherence, and display signatures of ballistic (dissipationless) transport.

    • M. Wurdack
    • , E. Estrecho
    •  & E. A. Ostrovskaya
  • Article
    | Open Access

    The nonequilibrium regime provides an exciting frontier in the search for novel quantum phases of matter. Here, the authors show that optically driving a lightly-doped semiconductor can lead to the spontaneous formation of a dynamical quantum liquid crystalline phase with a rotating magnetization.

    • Iliya Esin
    • , Gaurav Kumar Gupta
    •  & Netanel H. Lindner
  • Article
    | Open Access

    The nonlinear Hall effect is a quantum phenomenon, in which two perpendicular currents induce a Hall voltage; however, previous theories for this effect has remained at the semi classical level. Here, the authors develop a full quantum theory of the nonlinear Hall effect by using the diagrammatic technique.

    • Z. Z. Du
    • , C. M. Wang
    •  & X. C. Xie
  • Article
    | Open Access

    Two-dimensional hybrid perovskites exhibiting Rashba/Dresselhaus spin-splitting can be potentially used for spin-selective transport and spin-orbitronics, yet the structural determinants of spin-splitting are not well-understood. Here, the authors reveal a specific inorganic layer distortion that correlates with bulk spin-splitting in these materials.

    • Manoj K. Jana
    • , Ruyi Song
    •  & David B. Mitzi
  • Article
    | Open Access

    Advanced fabrication techniques enable a wide range of quantum devices, such as the realization of a topological qubit. Here, the authors introduce an on-chip fabrication technique based on shadow walls to implement topological qubits in an InSb nanowire without fabrication steps such as lithography and etching.

    • Sebastian Heedt
    • , Marina Quintero-Pérez
    •  & Leo P. Kouwenhoven
  • Article
    | Open Access

    Twisted monolayer-bilayer graphene is an attractive platform to study the interplay between topology, magnetism and correlations in the flat bands. Here, using electrical transport measurements, the authors uncover a rich correlated phase diagram and identify a new insulating state that can be explained by intervalley coherence with broken time reversal symmetry.

    • Minhao He
    • , Ya-Hui Zhang
    •  & Matthew Yankowitz
  • Article
    | Open Access

    Photomutiplication-type organic photodetectors (PM-OPDs) are attractive for various next-generation technologies due to their lower cost, higher sensitivity and technological utility. Here, the authors report vacuum-processed narrowband PM-OPDs with enhanced sub-bandgap external quantum efficiency.

    • Jonas Kublitski
    • , Axel Fischer
    •  & Karl Leo
  • Article
    | Open Access

    Up-conversion photoluminescence in colloidal quantum dots is generally believed to be mediated by thermal activation from defect states. Here, the authors reveal that highly-efficient up-conversion photoluminescence instead is related to electron-phonon coupling.

    • Zikang Ye
    • , Xing Lin
    •  & Xiaogang Peng
  • Article
    | Open Access

    The relation between the microscopic structure and the optical properties of atomic defects in 2D semiconductors is still debated. Here, the authors correlate different fabrication processes, optical spectroscopy and electron microscopy to identify the optical signatures of chalcogen vacancies in monolayer MoS2.

    • Elmar Mitterreiter
    • , Bruno Schuler
    •  & Christoph Kastl
  • Article
    | Open Access

    Accurate control of the spatial location and the emission wavelength of single photon emitters (SPEs) in van der Waals materials is a crucial yet challenging endeavour. Here, the authors use an electron beam to generate SPE ensembles in high purity synthetic hBN with enhanced spatial accuracy and emission reproducibility.

    • Clarisse Fournier
    • , Alexandre Plaud
    •  & Aymeric Delteil
  • Article
    | Open Access

    Previous research showed the existence of Rydberg excitons with large principle quantum numbers in Cu2O. Here, by using two-color pump-probe optical spectroscopy, the authors demonstrate the generation and control of long-range correlations between these giant Rydberg excitons, leading to exciton blockade.

    • Julian Heckötter
    • , Valentin Walther
    •  & Marc Aßmann
  • Article
    | Open Access

    Combining magnetic and semiconducting properties in a single material offers great technological potential, all the more so if these are coupled with good optical properties. Here, Neumann et al. present a Manganese doped Ruddlesden-Popper perovskite with this trifecta of attributes.

    • Timo Neumann
    • , Sascha Feldmann
    •  & Felix Deschler
  • Article
    | Open Access

    Recent theory has shown that the non-equilibrium response of a Kondo model can be described by the Fermi liquid theory with three-body correlations. Here, the authors experimentally measure such correlations in the nonlinear conductance of a Kondo-correlated quantum dot.

    • Tokuro Hata
    • , Yoshimichi Teratani
    •  & Kensuke Kobayashi
  • Article
    | Open Access

    Multielectron quantum dots offer a promising platform for high-performance spin qubits; however, previous demonstrations have been limited to single-qubit operation. Here, the authors report a universal gate set and two-qubit Bell state tomography in a high-occupancy double quantum dot in silicon.

    • Ross C. C. Leon
    • , Chih Hwan Yang
    •  & Andrew S. Dzurak
  • Article
    | Open Access

    The coexistence of spin–orbit and electron–electron interactions is expected to give rise to novel electronic phases and spin textures, but it is challenging to achieve in experiments. Here the authors realize such a regime in a two-dimensional electron system at a MgZnO/ZnO interface, by tuning the carrier density.

    • D. Maryenko
    • , M. Kawamura
    •  & M. Kawasaki
  • Article
    | Open Access

    Here, Yumoto et al. demonstrate that for a halide perovskite with large spin-orbit splitting the optical Stark effect can give way to a three level Autler-Townes effect in the near-infrared region. The multiband nature of the effect potentially allows for further optical control over quantum states.

    • Go Yumoto
    • , Hideki Hirori
    •  & Yoshihiko Kanemitsu
  • Article
    | Open Access

    Information transfer between distant qubits suffers from spurious interactions and disorder. Here, the authors report up to an order of magnitude enhancement in the quality factor of a swap operation of eigenstates in a quantum dot chain, by using a periodic driving protocol inspired by discrete time crystals.

    • Haifeng Qiao
    • , Yadav P. Kandel
    •  & John M. Nichol
  • Article
    | Open Access

    Though literature reports magnetoelectroluminescence (MEL) affects in organic light‐emitting diodes (OLEDs), probing the organic layer’s effective spin polarization remains a challenge. Here, the authors utilize dual singlet‐triplet emitting OLEDs to reveal the spin polarization in the materials.

    • Tobias Scharff
    • , Wolfram Ratzke
    •  & John M. Lupton
  • Article
    | Open Access

    Thin film deposition of perovskites by antisolvent engineering is commonly used, but the effect of processing parameters is not yet fully understood. Here, the authors identify two key factors that influence the film quality through a detailed structural and compositional study of perovskite layers fabricated by 14 different antisolvents.

    • Alexander D. Taylor
    • , Qing Sun
    •  & Yana Vaynzof
  • Article
    | Open Access

    Here, the authors show that the photoluminescence of MoSe2/WSe2 heterobilayers is dominated by valley-direct excitons, whereas, in heterotrilayers, interlayer hybridization turns momentum-indirect interlayer excitons into energetically lowest states with phonon-assisted emission.

    • Michael Förg
    • , Anvar S. Baimuratov
    •  & Alexander Högele
  • Article
    | Open Access

    Defect states in perovskites dictate the charge carriers behaviour, thus the ultimate optical and electrical properties. Here, the authors in-situ investigate trapped carrier dynamics in MAPbI3 thin films with ultra-fast temporal and high energetic resolution by means of ultrafast photocurrent spectroscopy.

    • Kanishka Kobbekaduwa
    • , Shreetu Shrestha
    •  & Jianbo Gao
  • Article
    | Open Access

    Here, the authors report on the large twist-angle susceptibility of excitons involving upper conduction bands in transition metal dichalcogenide bilayers. These high-lying excitons couple with band-edge excitons, and give rise to nonlinear quantum-optical processes that become tuneable by twisting.

    • Kai-Qiang Lin
    • , Paulo E. Faria Junior
    •  & John M. Lupton
  • Article
    | Open Access

    Previous interference experiments on indirect excitons found dislocation-like phase singularities that could not be explained by common phase defects. Here, the authors explain these features in terms of the moiré pattern of interference of condensate matter waves propagating over macroscopic distances.

    • J. R. Leonard
    • , Lunhui Hu
    •  & A. C. Gossard
  • Article
    | Open Access

    Here, the authors report intrinsic donor bound dark exciton states with associated phonon replicas in monolayer WSe2, and defect control crystal synthesis for the deterministic creation of these states.

    • Pasqual Rivera
    • , Minhao He
    •  & Xiaodong Xu
  • Article
    | Open Access

    Here, a strong nonlinearity of the gate-induced tunnel junction in bilayer graphene is used for efficient terahertz detection. The improved signal-to-noise ratio, as compared to conventional detectors, offers the application of steep-switching transistors in terahertz technology.

    • I. Gayduchenko
    • , S. G. Xu
    •  & D. A. Bandurin
  • Article
    | Open Access

    Fidelity control is important to quantum metrology and fault-tolerant quantum computation. Here, authors realize clock-controlled transfer of electrons through quantum dots and describe the statistics of accumulated charge by a random-walk model, achieving a benchmark for single-electron circuits.

    • David Reifert
    • , Martins Kokainis
    •  & Niels Ubbelohde
  • Article
    | Open Access

    In one-dimensional systems, the combination of a strong spin-orbit interaction and an applied magnetic field can give rise to a spin-gap, however experimental identification is difficult. Here, the authors present new signatures for the spin-gap, and verify these experimentally in hole QPCs.

    • K. L. Hudson
    • , A. Srinivasan
    •  & A. R. Hamilton
  • Article
    | Open Access

    Semiconductor spin-qubits with CMOS compatible architectures could benefit from the industrial capacity of the semiconductor industry. Here, the authors make the first steps in demonstrating this by showing single electron operations within a two-dimensional array of foundry-fabricated quantum dots.

    • Fabio Ansaloni
    • , Anasua Chatterjee
    •  & Ferdinand Kuemmeth
  • Article
    | Open Access

    One advantage of van der Waals materials is the ability to combine different materials in layers to form new heterostructures. Here, the authors investigate heterostructures of CrBr3 and MoSe2, and find that the ferromagnetism of CrBr3 enhances the valley dependent optical response of the MoSe2.

    • T. P. Lyons
    • , D. Gillard
    •  & A. I. Tartakovskii
  • Article
    | Open Access

    Here, the authors show that the properties of the moiré excitons in twisted van der Waals bilayers of transition metal dichalcogenides are determined by the moiré reciprocal lattice period, and can be controlled via twist-angle tuning.

    • Long Zhang
    • , Zhe Zhang
    •  & Hui Deng
  • Article
    | Open Access

    Skyrmions, topological spin textures, are typically stabilized by the Dzyaloshinskii-Moriya interaction and an applied magnetic field. In this theoretical study, by analysing monolayer NiI2, the authors suggest that two-site anisotropy with magnetic frustration can stabilize a skyrmion lattice.

    • Danila Amoroso
    • , Paolo Barone
    •  & Silvia Picozzi
  • Article
    | Open Access

    Designing efficient nanowire chip-based electrical and optical devices remains a challenge. Here, the authors present an axial p-n junction GaAs nanowire X-ray detector that enables achieving a spatial resolution of 200 nm; probing the internal electrical field and observing hot electron effects at the nanoscale.

    • Maximilian Zapf
    • , Maurizio Ritzer
    •  & Carsten Ronning
  • Article
    | Open Access

    Inversion asymmetry imparts rich condensed matter phenomena in inorganic systems, and transmission of chirality across structural motifs is an attractive design strategy to break symmetry. Here, the authors use chiral organic cations to transfer structural chirality to inorganic layers in hybrid perovskites.

    • Manoj K. Jana
    • , Ruyi Song
    •  & David B. Mitzi