Research Briefing |
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Article
| Open AccessDipolar skyrmions and antiskyrmions of arbitrary topological charge at room temperature
Control over magnetic skyrmions at room temperature has important applications in technology. Now the observation of skyrmions with high topological charge widens the potential for them to be used in unconventional computing techniques.
- Mariam Hassan
- , Sabri Koraltan
- & Manfred Albrecht
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Article |
Rich proton dynamics and phase behaviours of nanoconfined ices
The phase diagram of confined ice is different from that of bulk ice. Simulations now reveal several 2D ice phases and show how strong nuclear quantum effects result in rich proton dynamics in 2D confined ices.
- Jian Jiang
- , Yurui Gao
- & Xiao Cheng Zeng
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Article |
Room-temperature long-range ferromagnetic order in a confined molecular monolayer
Realizing robust ferromagnetic order in two dimensions is challenging as an underlying crystalline framework is normally required. Now room-temperature ferromagnetism is demonstrated in a two-dimensional honeycomb self-assembly of confined molecules.
- Yuhua Liu
- , Haifeng Lv
- & Yi Xie
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Article |
Reconfigurable quantum fluid molecules of bound states in the continuum
Bound states in the continuum are topological states with useful symmetry protection properties. An experiment now shows how to use them to form macroscopically coherent complexes of polariton condensates.
- Antonio Gianfrate
- , Helgi Sigurðsson
- & Daniele Sanvitto
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News & Views |
When excitons crystallize
Semiconducting dipolar excitons — bound states of electrons and holes — in artificial moiré lattices constitute a promising condensed matter system to explore the phase diagram of strongly interacting bosonic particles.
- Nadine Leisgang
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Article
| Open AccessModulated Kondo screening along magnetic mirror twin boundaries in monolayer MoS2
Interactions between a localized magnetic moment and electrons in a metal can produce an emergent resonance that affects the metal’s properties. A realization of this Kondo effect in MoS2 provides an opportunity to study it in microscopic detail.
- Camiel van Efferen
- , Jeison Fischer
- & Wouter Jolie
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Article
| Open AccessCoupling to octahedral tilts in halide perovskite nanocrystals induces phonon-mediated attractive interactions between excitons
Time-resolved measurements show that coupling between electrons and phonons in lead halide perovskites can mediate attractive interactions between excitons, although the interaction strength depends on the specific material.
- Nuri Yazdani
- , Maryna I. Bodnarchuk
- & Aaron M. Lindenberg
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Article |
Valley-polarized excitonic Mott insulator in WS2/WSe2 moiré superlattice
Interactions between excitons and correlated electrons can lead to the formation of interesting states. Now, evidence suggests that these interactions can give rise to a Mott insulator of excitons.
- Zhen Lian
- , Yuze Meng
- & Su-Fei Shi
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Article |
Evidence for spinarons in Co adatoms
Despite the theoretical prediction of spinaron quasiparticles in artificial nanostructures, experimental evidence has not yet been seen. Now it has been observed in a hybrid system comprising Co atoms on a Cu(111) surface.
- Felix Friedrich
- , Artem Odobesko
- & Matthias Bode
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Article
| Open AccessEvidence of finite-momentum pairing in a centrosymmetric bilayer
Cooper pairs that form with finite centre-of-mass momentum are rare. Now there is evidence that this can happen below the Pauli limit in a bilayer material.
- Dong Zhao
- , Lukas Debbeler
- & Jurgen Smet
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Article |
Observation of the boson peak in a two-dimensional material
The boson peak refers to an excess in the phonon density of states seen in three-dimensional amorphous materials. Helium-atom scattering experiments have now revealed a boson peak in a two-dimensional material, too, at a frequency similar to that of the bulk material.
- Martin Tømterud
- , Sabrina D. Eder
- & Bodil Holst
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Article
| Open AccessCoulomb-correlated electron number states in a transmission electron microscope beam
Coulomb interactions in free-electron beams are usually seen as an adverse effect. The creation of distinctive number states with one, two, three and four electrons now reveals unexpected opportunities for electron microscopy and lithography from Coulomb correlations.
- Rudolf Haindl
- , Armin Feist
- & Claus Ropers
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News & Views |
Noncollinear spin textures with a twist
Generating and controlling noncollinear spin textures is a promising route towards developing next-generation logic architectures beyond CMOS. Now, these spin textures can be engineered in twisted magnetic two-dimensional materials.
- Bevin Huang
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Article |
Evidence of non-collinear spin texture in magnetic moiré superlattices
A moiré potential may play a role in determining the magnetic properties of a two-dimensional homo or heterostructure. Now, non-collinear spin structures are observed in twisted double bilayer CrI3, providing a platform to engineer unusual magnetic textures.
- Hongchao Xie
- , Xiangpeng Luo
- & Liuyan Zhao
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Article
| Open AccessPhotonic metamaterial analogue of a continuous time crystal
So far, a continuous time crystal has only been implemented on a quantum system. Optically driven many-body interactions in a nanomechanical photonic metamaterial now allow the realization of a classical continuous time crystal.
- Tongjun Liu
- , Jun-Yu Ou
- & Nikolay I. Zheludev
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Article |
Layer-by-layer disentanglement of Bloch states
Layering quantum materials can produce interesting phenomena by combining the different behaviour of electronic states in each layer. A layer-sensitive measurement technique provides insights into the physics of a magnetic topological insulator.
- Woojoo Lee
- , Sebastian Fernandez-Mulligan
- & Shuolong Yang
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Letter |
Detection of a plasmon-polariton quantum wave packet
Plasmonics allows precise engineering of light–matter interactions and is the driver behind many optical devices. The local observation of a plasmonic quantum wave packet is a step towards bringing these functionalities to the quantum regime.
- Sebastian Pres
- , Bernhard Huber
- & Tobias Brixner
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Article |
Quantum simulation of an exotic quantum critical point in a two-site charge Kondo circuit
The quantum critical behaviour of a two-impurity Kondo model variant is observed in a system of hybrid-semiconductor islands that could provide a scalable platform for solid-state quantum simulation
- Winston Pouse
- , Lucas Peeters
- & David Goldhaber-Gordon
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Article |
Josephson–Coulomb drag effect between graphene and a LaAlO3/SrTiO3 superconductor
Transport measurements between a normal conductor and superconductor show that in this case, the Coulomb drag response can be much larger than that between two normal conductors.
- Ran Tao
- , Lin Li
- & Changgan Zeng
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Letter |
Floquet engineering of strongly driven excitons in monolayer tungsten disulfide
The interaction of strong laser fields with tungsten disulfide leads to light-dressed Floquet replica of excitonic states, which manifest as new features in the transient absorption spectrum.
- Yuki Kobayashi
- , Christian Heide
- & Shambhu Ghimire
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Article |
Spin–orbit–parity coupled superconductivity in atomically thin 2M-WS2
A form of superconductivity where strong spin–orbit coupling combines with topological band inversions to produce strong robustness against magnetic fields is shown in a few-layer transition metal dichalcogenide.
- Enze Zhang
- , Ying-Ming Xie
- & Shaoming Dong
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Article |
Quantum microscopy with van der Waals heterostructures
Hexagonal boron nitride is a common component of 2D heterostructures. Defects implanted in boron nitride crystals can be used to perform spatially resolved sensing of properties, including temperature, magnetism and current.
- A. J. Healey
- , S. C. Scholten
- & J.-P. Tetienne
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Article |
Evidence for a spinon Kondo effect in cobalt atoms on single-layer 1T-TaSe2
Unconventional quasiparticles carrying spin but not electric charge emerge in quantum spin liquid phases. The Kondo interaction of these spinon quasiparticles with magnetic impurities may now have been observed.
- Yi Chen
- , Wen-Yu He
- & Michael F. Crommie
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Letter |
Anomalous Hall effect at half filling in twisted bilayer graphene
The anomalous Hall effect can signify that a material has a spontaneous magnetic order. Now, twisted bilayer graphene shows this effect at half filling, suggesting that the ground state is valley-polarized.
- Chun-Chih Tseng
- , Xuetao Ma
- & Matthew Yankowitz
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News & Views |
Magnetic skyrmions unwrapped
Experiments with chiral magnets may hold the key to a better understanding of fundamental aspects of transformations between different skyrmionic states, necessary for magnetic memory and logic applications to become a reality.
- Alexey A. Kovalev
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Letter |
Excitonic insulator in a heterojunction moiré superlattice
Stacking monolayer WS2 on top of bilayer WSe2 creates conditions where electrons and holes can coexist in the structure. Their Coulomb interaction allows them to form bound pairs and hence an excitonic insulator state.
- Dongxue Chen
- , Zhen Lian
- & Su-Fei Shi
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Article
| Open AccessSuperconducting quantum interference at the atomic scale
Continuously changing the coupling between a magnetic impurity and a superconductor allows the observation of the reversal of supercurrent flow at the atomic scale.
- Sujoy Karan
- , Haonan Huang
- & Christian R. Ast
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News & Views |
Harmonic generation in confinement
Quantum confinement effects offer a more comprehensive understanding of the fundamental processes that drive extreme optical nonlinearities in nano-engineered solids, opening a route to unlocking the potential of high-order harmonic generation.
- Julien Madéo
- & Keshav M. Dani
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Letter |
Size-controlled quantum dots reveal the impact of intraband transitions on high-order harmonic generation in solids
Both inter- and intraband transitions contribute to high-harmonic generation in solids, but their exact roles are not fully understood. Experiments with quantum dots show that enhanced intraband transitions lead to increased carrier injection and thus enhanced harmonic generation.
- Kotaro Nakagawa
- , Hideki Hirori
- & Yoshihiko Kanemitsu
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Letter
| Open AccessSkyrmion–antiskyrmion pair creation and annihilation in a cubic chiral magnet
Magnetic skyrmions—a type of localized spin texture—have been theoretically predicted to annihilate with counterparts known as antiskyrmions. By means of electron microscopy, such annihilation has now been observed in a cubic chiral magnet.
- Fengshan Zheng
- , Nikolai S. Kiselev
- & Rafal E. Dunin-Borkowski
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News & Views |
Long-range order seen at last
Advances in precision lithography and measurement have made it possible to observe and control the magnetic phase transition in kagome artificial spin ice, which could lead to new technological devices.
- Susan Kempinger
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Article
| Open AccessDirectional ballistic transport in the two-dimensional metal PdCoO2
Electrons in PdCoO2 can travel a long way before being scattered, and their band structure is such that they can travel in only one of three directions. As a result, the current flow through this nanoscale conductor can be very efficient.
- Maja D. Bachmann
- , Aaron L. Sharpe
- & Philip J. W. Moll
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Article |
Real-space imaging of phase transitions in bridged artificial kagome spin ice
Artificial spin ice formed of nanomagnets arranged on a lattice mimics frustrated magnetism seen in condensed matter. By controlling magnetic interactions, theoretically predicted phase transitions are now observed in artificial kagome-lattice spin ice.
- Kevin Hofhuis
- , Sandra Helen Skjærvø
- & Laura Jane Heyderman
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Letter |
Direct observation of a dynamical glass transition in a nanomagnetic artificial Hopfield network
A spin glass is a disordered system with randomized competing magnetic interactions. Now, a metamaterial artificial spin glass based on nanomagnets is reported, with rudimentary features of a neural network.
- Michael Saccone
- , Francesco Caravelli
- & Alan Farhan
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Article |
Strained crystalline nanomechanical resonators with quality factors above 10 billion
Soft clamping reduces the dissipation of nanomechanical resonators, but this method has been limited to amorphous materials. When applied in crystalline silicon, it enables resonators with quality factors beyond ten billion.
- A. Beccari
- , D. A. Visani
- & T. J. Kippenberg
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News & Views |
Optical energy on demand
Light travels through disordered media on a random path that is hard to control. A comprehensive study has now shown that optical energy can be deposited at a desired depth in a disordered waveguide by injecting a light field with a particular shape.
- Oluwafemi S. Ojambati
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Letter |
Twist engineering of the two-dimensional magnetism in double bilayer chromium triiodide homostructures
Stacking and twisting two-dimensional materials has led to the observation of a variety of electronic phenomena. Now, magnetic behaviour that is distinct from anything seen in individual layers is induced by a moiré pattern in double bilayer chromium triiodide.
- Hongchao Xie
- , Xiangpeng Luo
- & Liuyan Zhao
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News & Views |
A layered unconventional superconductor
Most systems exhibiting topological superconductivity are artificial structures that require precise engineering. Now, a layered material shows tantalizing signs of the phenomenon.
- Jose L. Lado
- & Peter Liljeroth
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Article |
Observation of interband collective excitations in twisted bilayer graphene
Moiré potentials substantially alter the electronic properties of twisted bilayer graphene at a magic twist angle. A propagating plasmon mode, which can be observed with optical nano-imaging, is associated with transitions between the moiré minibands.
- Niels C. H. Hesp
- , Iacopo Torre
- & Frank H. L. Koppens
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Letter |
Imaging local discharge cascades for correlated electrons in WS2/WSe2 moiré superlattices
The Hubbard model describes many fascinating phenomena, but relating it to complicated quantum materials is difficult. Now, atomic-resolution measurements can estimate the interaction parameters that appear in the model for real materials.
- Hongyuan Li
- , Shaowei Li
- & Feng Wang
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News & Views |
Quantum sensors go flat
Some material defects have quantum degrees of freedom that are measurably disturbed by environmental changes, making them excellent sensors. A two-dimensional material with such defects could improve the versatility of quantum-sensing technologies.
- J.-P. Tetienne
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Article |
Nanoscale Turing patterns in a bismuth monolayer
Macroscale patterns seen in biological systems such as animal coats or skin can be described by Turing’s reaction–diffusion theory. Now Turing patterns are shown to also exist in bismuth monolayers, an exemplary nanoscale atomic system.
- Yuki Fuseya
- , Hiroyasu Katsuno
- & Aharon Kapitulnik
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Article |
Two-fold symmetric superconductivity in few-layer NbSe2
A two-fold rotational symmetry is observed in the superconducting state of NbSe2. This is strikingly different from the three-fold symmetry of the lattice, and suggests that a mixed conventional and unconventional order parameter exists in this material.
- Alex Hamill
- , Brett Heischmidt
- & Vlad S. Pribiag
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Letter |
Correlated insulating states at fractional fillings of the WS2/WSe2 moiré lattice
Twisted bilayers of WS2 and WSe2 have correlated states that correspond to real-space ordering of the electrons on a length scale much longer than the moiré pattern.
- Xiong Huang
- , Tianmeng Wang
- & Yong-Tao Cui
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Letter |
Nanoscale mechanics of antiferromagnetic domain walls
High-resolution magnetometry shows that the shape of domain walls in Cr2O3 is determined by the energetic cost of their surface area. The walls behave like elastic surfaces that avoid thicker parts of the sample where they would need to be larger.
- Natascha Hedrich
- , Kai Wagner
- & Patrick Maletinsky
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Letter |
Deep moiré potentials in twisted transition metal dichalcogenide bilayers
The electrical potential created by a moiré pattern in twisted transition metal dichalcogenide bilayers can be surprisingly deep, trapping electrons that can possibly be used for opto-electronic or quantum simulation applications.
- Sara Shabani
- , Dorri Halbertal
- & Abhay N. Pasupathy
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