Sonny Rhim

Nature, Published online: 08 March 2024; doi:10.1038/d41586-024-00652-1

Batteries that store photons in atoms or molecules could retain their efficiency with wireless charging.

Author(s): Niladri Banerjee and Jason W. A. Robinson

A quantum phase of matter detected in an iron-based superconductor could host Majorana zero modes—quasiparticles that may serve as building blocks for future quantum computers.

[Physics 16, 47] Published Mon Mar 27, 2023

Author(s): Jens Schulenborg, Svend Krøjer, Michele Burrello, Martin Leijnse, and Karsten Flensberg

Reading out the parity degree of freedom of Majorana bound states is key to demonstrating their non-Abelian exchange properties. Here, we present a low-energy model describing localized edge states in a two-arm device. We study parity-to-charge conversion based on coupling the superconductor bound s…

[Phys. Rev. B 107, L121401] Published Fri Mar 03, 2023

Author(s): Hisashi Kotegawa, Toshiaki Uga, Hideki Tou, Eiichi Matsuoka, and Hitoshi Sugawara

Cubic CeZn shows a structural phase transition under pressure and it modifies the ground state from an antiferromagnetic (AFM) state to a ferromagnetic (FM) state. To investigate how the FM state terminates at a quantum phase transition, we measured the electrical resistivity under pressure for a si…

[Phys. Rev. B 106, L180405] Published Wed Nov 23, 2022

Nature Reviews Physics, Published online: 21 November 2022; doi:10.1038/s42254-022-00540-5

Matthew Horton introduces pymatgen, a free and open source code that can be used for materials screenings.

Author(s): Osakpolor Eki Obakpolor and Pavan Hosur

Weyl semimetals famously host a surface topological metal containing open Fermi arcs instead of closed Fermi surfaces. Here, the authors predict another surface feature, Luttinger arcs, that form closed loops with the Fermi arcs in undoped Weyl semimetals. Luttinger arcs are common, albeit experimentally inaccessible, for strongly interacting electrons. Here, they occur even without interactions and switch places with Fermi arcs for different surface terminations – a property the authors exploit to pinpoint Luttinger arcs for Co and Sn terminations in Co3Sn2S2.

[Phys. Rev. B 106, L081112] Published Mon Aug 15, 2022

Author(s): Pablo Aguado-Puente and Piotr Chudzinski

One of the key issues in the physics of topological insulators is whether the topologically nontrivial properties survive at finite temperatures and, if so, whether they disappear only at the temperature of topological gap closing. Here, we study this problem, using quantum fidelity as a measure, by…

[Phys. Rev. B 106, L081103] Published Fri Aug 05, 2022

Author(s): Rachel Berkowitz

More frequencies of light can pass between two coupled wavy waveguides than between two coupled straight ones, something that could allow for more flexible designs of optics-based circuits on silicon chips.

[Physics 15, s100] Published Tue Jul 26, 2022

Author(s): Fernando Ajejas, Yanis Sassi, William Legrand, Sophie Collin, Jose Peña Garcia, André Thiaville, Stefania Pizzini, Nicolas Reyren, Vincent Cros, and Albert Fert

The actual mechanisms occurring at interfaces underlying the Dzyaloshinskii-Moriya interaction (DMI) remain a question in nanomagnetism. In this study, we investigate the origin of the interfacial DMI, aiming at estimating how independent the DMI contributions of the two interfaces of a FM layer are…

[Phys. Rev. Materials 6, L071401] Published Tue Jul 05, 2022

Author(s): Peize Ding, Ching Hua Lee, Xianxin Wu, and Ronny Thomale

Layered kagome metals AV3Sb5 (A=K,Rb,Cs) exhibit diverse correlated electron phenomena. They include charge density wave formation and superconductivity, the pairing symmetry of which, however, is controversial due to contradictory experimental evidence. Through calculations based on real-space latt…

[Phys. Rev. B 105, 174518] Published Thu May 26, 2022

Author(s): Bo-Yao Wang, Jing-Yu Ning, Tzu-Hsin Li, Chun-Chieh Chung, Chun-Yao Hsu, Ming-Shian Tsai, Tzu-Hung Chuang, and Der-Hsin Wei

Ferromagnetic (FM) films with higher magnetic moment density typically exhibit sizable in-plane magnetic anisotropy as a result of strong dipolar interactions, which hinder their application in state-of-the-art perpendicularly based magnetic devices. This study reports the effects of triggering the …

[Phys. Rev. B 105, 184415] Published Fri May 13, 2022

Harmonic analysis is a powerful tool to characterize and quantify current-induced torques acting on magnetic materials, but so far it remains an open question in studying antiferromagnets. Here we formulate a general theory of harmonic Hall responses of collinear antiferromagnets driven by current-induced torques including both field-like and damping-like components. By scanning a magnetic field of variable strength in three orthogonal planes, we are able to distinguish the contributions from field-like torque, damping-like torque, and concomitant thermal effects by analyzing the second harmonic signals in the Hall voltage. The analytical expressions of the first and second harmonics as functions of the magnetic field direction and strength are confirmed by numerical simulations with good agreement. We demonstrate our predictions in two prototype antiferromagnets, $\alpha-$Fe$_{2}$O$_{3}$ and NiO, providing direct and general guidance to current and future experiments.

Nature Nanotechnology, Published online: 11 April 2022; doi:10.1038/s41565-022-01089-1

A preclinical study reports a platform for the generation of dendritic cell-derived nanovesicles with enhanced immunostimulatory function, which demonstrate promising antitumoural activity in mouse models and might overcome some of the shortcomings of early-generation dendritic cell nanovaccines.

Nature Communications, Published online: 08 April 2022; doi:10.1038/s41467-022-29545-5

Tunable coupling between magnetism and the lattice is important for on-demand manipulation of magnetic phases. Here, the authors demonstrate that lattice vibrations can coherently modulate the interlayer magnetic exchange coupling in the magnetic topological insulator MnBi2Te4.

Machine learning (ML) models utilizing structure-based features provide an efficient means for accurate property predictions across diverse chemical spaces. However, obtaining equilibrium crystal structures typically requires expensive density functional theory (DFT) calculations, which limits ML-based exploration to either known crystals or a small number of hypothetical crystals. Here, we demonstrate that the application of Bayesian optimization with symmetry constraints using a graph deep learning energy model can be used to perform "DFT-free" relaxations of crystal structures. Using this approach to significantly improve the accuracy of ML-predicted formation energies and elastic moduli of hypothetical crystals, two novel ultra-incompressible hard materials MoWC2 (P63/mmc) and ReWB (Pca21) were identified and successfully synthesized via in-situ reactive spark plasma sintering from a screening of 399,960 transition metal borides and carbides. This work addresses a critical bottleneck to accurate property predictions for hypothetical materials, paving the way to ML-accelerated discovery of new materials with exceptional properties.

Author(s): J. Settino, N. Lo Gullo, F. Plastina, and A. Minguzzi

The single-particle spectral function of a strongly correlated system is an essential ingredient to describe its dynamics and transport properties. We develop a method to evaluate exactly the spectral function for a gas of one-dimensional bosons with infinitely strong repulsions valid for any type o...

[Phys. Rev. Lett. 126, 065301] Published Tue Feb 09, 2021

Nature, Published online: 24 November 2020; doi:10.1038/d41586-020-03291-4

COVID-19: students caught in Pakistan’s digital divide

Author(s): Maria Teresa Mercaldo, Paolo Solinas, Francesco Giazotto, and Mario Cuoco

We investigate the physical mechanisms for achieving an electrical control of conventional spin-singlet superconductivity in thin films by focusing on the role of surface orbital polarization. Assuming a multiorbital description of the metallic state, due to screening effects the electric field acts...

[Phys. Rev. Applied 14, 034041] Published Tue Sep 15, 2020

Author(s): Fatemeh Nematollahi, S. Azar Oliaei Motlagh, Jhih-Sheng Wu, Rupesh Ghimire, Vadym Apalkov, and Mark I. Stockman

We study theoretically the ultrafast electron dynamics of three-dimensional Weyl semimetals in the field of a laser pulse. For a circularly polarized pulse, such dynamics is governed by topological resonance, which manifests itself as a specific conduction band population distribution in the vicinit...

[Phys. Rev. B 102, 125413] Published Wed Sep 09, 2020

Author(s): Masaki Imai, Hiroyuki Chudo, Mamoru Matsuo, Sadamichi Maekawa, and Eiji Saitoh

In a certain kind of ferrimagnets, the net spin angular momentum in the magnet vanishes at a certain temperature, called the angular momentum compensation temperature (TA). The angular momentum compensation is key for high-speed magnetic devices because the magnetization can be swiftly switched due to no inertia of the spin angular momentum accompanied by the magnetic moment. Here, the authors have discovered that the NMR signal is enhanced at TA due to the enhancement of the domain wall mobility. This discovery paves the way to exploring new materials possessing the angular momentum compensation.

[Phys. Rev. B 102, 014407] Published Mon Jul 06, 2020

Nature Physics, Published online: 25 May 2020; doi:10.1038/s41567-020-0910-0

A careful study of quantum oscillations of single crystals of the cuprate superconductor YBCO placed under a magnetic field reveals a sawtooth behaviour that is reminiscent of two-dimensional electronic systems—in turn suggesting the existence of a so-called ‘hard antinodal gap’ in this system.

Author(s): Avik Ghosh

A semimetal nanowire with topological properties carries spin-polarized electron currents that can be switched with a voltage.

[Physics 13, 38] Published Mon Mar 16, 2020

In the fundamental laws of physics, gauge fields mediate the interaction between charged particles. An example is the quantum theory of electrons interacting with the electromagnetic field, based on U(1) gauge symmetry. Solving such gauge theories is in general a hard problem for classical computational techniques. Although quantum computers suggest a way forward, large-scale digital quantum devices for complex simulations are difficult to build. We propose a scalable analog quantum simulator of a U(1) gauge theory in one spatial dimension. Using interspecies spin-changing collisions in an atomic mixture, we achieve gauge-invariant interactions between matter and gauge fields with spin- and species-independent trapping potentials. We experimentally realize the elementary building block as a key step toward a platform for quantum simulations of continuous gauge theories.

The coupling between spin and charge degrees of freedom in a crystal imparts strong optical signatures on scattered electromagnetic waves. This has led to magneto-optical effects with a host of applications, from the sensitive detection of local magnetic order to optical modulation and data storage technologies. Here, we demonstrate a new magneto-optical effect, namely, the tuning of inelastically scattered light through symmetry control in atomically thin chromium triiodide (CrI$_3$). In monolayers, we found an extraordinarily large magneto-optical Raman effect from an A$_{1g}$ phonon mode due to the emergence of ferromagnetic order. The linearly polarized, inelastically scattered light rotates by ~40$^o$, more than two orders of magnitude larger than the rotation from MOKE under the same experimental conditions. In CrI$_3$ bilayers, we show that the same A$_{1g}$ phonon mode becomes Davydov-split into two modes of opposite parity, exhibiting divergent selection rules that depend on inversion symmetry and the underlying magnetic order. By switching between the antiferromagnetic states and the fully spin-polarized states with applied magnetic and electric fields, we demonstrate the magnetoelectrical control over their selection rules. Our work underscores the unique opportunities provided by 2D magnets for controlling the combined time-reversal and inversion symmetries to manipulate Raman optical selection rules and for exploring emergent magneto-optical effects and spin-phonon coupled physics.

Author(s): Igor S. Burmistrov, Moshe Goldstein, Mordecai Kot, Vladislav D. Kurilovich, and Pavel D. Kurilovich

Hydrodynamic charge transport is at the center of recent research efforts. Of particular interest is the nondissipative Hall viscosity, which conveys topological information in clean gapped systems. The prevalence of disorder in the real world calls for a study of its effect on viscosity. Here we ad...

[Phys. Rev. Lett. 123, 026804] Published Tue Jul 09, 2019

Author(s): Martin Hennecke, Ilie Radu, Radu Abrudan, Torsten Kachel, Karsten Holldack, Rolf Mitzner, Arata Tsukamoto, and Stefan Eisebitt

One of the key processes setting the speed of the ultrafast magnetization phenomena is the angular momentum transfer from and into the spin system. However, the way the angular momentum flows during ultrafast demagnetization and magnetization switching phenomena remains elusive so far. We report on ...

[Phys. Rev. Lett. 122, 157202] Published Fri Apr 19, 2019

Author(s): Seulong Kim and Kihong Kim

We study Anderson localization of massless two-dimensional Dirac electrons in random one-dimensional scalar and vector potentials theoretically for two different cases, in which the scalar and vector potentials are either uncorrelated or correlated. From the Dirac equation, we deduce the effective w...

[Phys. Rev. B 99, 014205] Published Thu Jan 17, 2019

Author(s): Hikaru Watanabe and Youichi Yanase

The multipole moment is an established concept of electrons in solids. Entanglement of spin, orbital, and sublattice degrees of freedom is described by the multipole moment, and spontaneous multipole order is a ubiquitous phenomenon in strongly correlated electron systems. In this paper, we present ...

[Phys. Rev. B 98, 245129] Published Wed Dec 19, 2018

Charge trapping and super-Poissonian noise centres in a cuprate superconductor

Charge trapping and super-Poissonian noise centres in a cuprate superconductor, Published online: 08 October 2018; doi:10.1038/s41567-018-0300-z

A new noise spectroscopy technique shows that charges localized as polarons trapped at impurity sites mediate perpendicular ‘c-axis’ electronic transport in cuprate superconductors.