| Volume 106, Issues 13 - 16 October 2022 | | Advertisement | The APS Science Trust Project was born out of member-demand to address misinformation about science, which has been increasing due to the broad accessibility of various streams of communication. This free virtual workshop, held on 4 consecutive Tuesdays, starting on November 29, 1:00 - 3:00 p.m. ET, via Zoom, will focus on climate change misinformation, but the skills and methods are appropriate for addressing a wide range of misinformation topics. Register now » | | | | |
Advertisement | Build your on-campus physics community with help from a Women in Physics Group Grant. The APS Committee on the Status of Women in Physics (CSWP) is now accepting proposals from undergraduate and graduate students who are interested in creating new WiP groups or enhancing existing ones. The deadline for proposals is November 21. Learn more » | | | | | | Not an APS member? Join today to start connecting with a community of more than 50,000 physicists. | | | | Jessica Thomas and Michael Thoennessen Phys. Rev. B 106, 130001 (2022) – Published 11 October 2022 | | | Editors' Suggestion Chao-Ming Jian, Bela Bauer, Anna Keselman, and Andreas W. W. Ludwig Phys. Rev. B 106, 134206 (2022) – Published 21 October 2022  | Entanglement dynamics in nonunitary quantum systems have been found to exhibit novel nonequilibrium quantum phase transitions and have attracted tremendous attention with connections to various aspects of quantum information theory. This work establishes, for systems of noninteracting fermions, an exact three-way correspondence between (i) nonunitary (as well as unitary) quantum circuits dynamics in d spatial dimensions; (ii) (d+1)-dimensional Gaussian tensor networks, and (iii) fermion systems in (d+1) spatial dimensions subject to unitary evolution with static Hamiltonians. Through this correspondence, d-dimensional random quantum circuits are connected with the classic subject area of Anderson localization in (d+1) spatial dimensions and consequently follow the "tenfold way'' Altland-Zirnbauer classification. Selected examples of quantum circuits exhibiting entanglement phases and criticalities are used to illustrate these general principles. | | | | | | Editors' Suggestion Li Ern Chern, Yong Baek Kim, and Claudio Castelnovo Phys. Rev. B 106, 134402 (2022) – Published 4 October 2022  | Geometric frustration in spin systems offers potential routes to realize unusual phases of matter. The authors consider emergent quantum spin liquids of interacting S=1/2 moments on the pyrochlore lattice with a breathing anisotropy, where two inequivalent sets of tetrahedra are present. They classify possible Z2 and U(1) quantum spin liquids in this system and find a small number of physically motivated candidates. In particular, two degenerate U(1) spin liquids are identified for the antiferromagnetic Heisenberg model. The degeneracy is robust with respect to tuning the breathing anisotropy, but it can be lifted by a finite Dzyaloshinskii-Moriya interaction. The effect of gauge fluctuations in a gapless U(1) spin liquid is investigated for comparison with future experiments. | | | | | | Editors' Suggestion L. Peedu, V. Kocsis, D. Szaller, B. Forrai, S. Bordács, I. Kézsmárki, J. Viirok, U. Nagel, B. Bernáth, D. L. Kamenskyi, A. Miyata, O. Portugall, Y. Tokunaga, Y. Tokura, Y. Taguchi, and T. Rõõm Phys. Rev. B 106, 134413 (2022) – Published 12 October 2022  | Magnetoelectric multiferroics feature crosscoupling between magnetic and charge order. Here, the authors study the absorption of electromagnetic radiation by spin waves in magnetoelectric LiFePO4 in the terahertz (THz) spectral range. Using linearly polarized THz radiation, they establish that there are spin waves that interact with magnetic and electric components of radiation. This is unusual for electron spins since they are susceptible to magnetic fields only. Another striking observation is that the number of spin-wave modes in the THz spectrum exceeds four times the number of modes expected for a four-spin system. Using the mean-field model and the magnetic field dependence of the THz spectra, the authors identify four conventional spin-wave modes in LiFePO4. It is proposed that other THz-active spin-wave modes are more exotic quadrupolar excitations, such as spin-stretching modes and two-magnon excitations. | | | | | | Editors' Suggestion W. G. Zheng, V. Balédent, E. Ressouche, V. Petricek, D. Bounoua, P. Bourges, Y. Sidis, A. Forget, D. Colson, and P. Foury-Leylekian Phys. Rev. B 106, 134429 (2022) – Published 24 October 2022  | A complex magnetic structure with specific symmetry properties is a relevant ingredient for magnetoelectric multiferroicity. In BaFe2Se3, a member of the Fe spin-ladder family of pressure-induced superconductors, the authors reveal this complexity. Using polarized and unpolarized single-crystal neutron diffraction, they evidence a chiral, umbrella-like magnetic order made of blocks of quasiferromagnetic spins, antiferromagnetically ordered along the ladder. Such accurate information on the magnetism will help to understand the magnetoelectric coupling in this family and its puzzling phase diagram. | | | | | | Editors' Suggestion Chae-Yeun Park and Michael J. Kastoryano Phys. Rev. B 106, 134437 (2022) – Published 31 October 2022  | Variational Monte Carlo with neural quantum states is one of the most powerful tools for solving the ground state of quantum many-body Hamiltonians. However, the performance of the method on frustrated Hamiltonians remains significantly worse than that of sign-free Hamiltonians, even though the method itself is free from sum-over alternating signs. Here, the authors systematically study numerical subtleties in restricted Boltzmann machine based variational Monte Carlo for solving Hamiltonians with the sign problem and unveil how quantum phases are related to the numerics. | | | | | | Editors' Suggestion Ekta Singh, Henrik Beccard, Zeeshan H. Amber, Julius Ratzenberger, Clifford W. Hicks, Michael Rüsing, and Lukas M. Eng Phys. Rev. B 106, 144103 (2022) – Published 19 October 2022  | Although ferroelectrics are electrical insulators, their domain walls (DWs) can be charged and can possess an exceptional large conductivity of an order of magnitude larger than in the bulk crystal. To shed light on the correlation between bound charges and conductivity of ferroelectric DWs, the authors in this work investigate the effect of piezoelectric charging via external uniaxial stress on the directionality of DW conductivity in single crystals of z-cut 5% MgO doped lithium niobate by combing a piezodriven stress cell with a scanning probe microscope. | | | | | | Editors' Suggestion Xiao-Qi Sun, Jing-Yuan Chen, and Steven A. Kivelson Phys. Rev. B 106, 144111 (2022) – Published 28 October 2022  | From a symmetry perspective, a magnetic field makes a material chiral and thus leads to a nonzero thermal Hall effect. However, recent experiments on a variety of interesting insulators – including a number of cuprates – have uncovered an unexpectedly large field-induced thermal Hall effect, despite the fact that there are no low-energy charge-carrying excitations, i.e., itinerant electrons. The authors propose here a mechanism of coupling a magnetic field to phonons and producing a thermal Hall response of the requisite magnitude through resonant skew scattering of phonons from a certain class of three-level systems. | | | | | | Editors' Suggestion Satoru Hayami Phys. Rev. B 106, 144402 (2022) – Published 4 October 2022  | An electric ferroaxial moment is a fundamental dipole moment like the ferroelectric, ferromagnetic, and ferromagnetic-toroidal moments. Nevertheless, its nature has been masked compared to the ferromagnetic and ferroelectric cases. Based on symmetry and microscopic-model analyses, the author reveals when and how such a ferroaxial entity appears in magnetic materials. It is demonstrated that a vortex spin configuration naturally induces a ferroaxial moment. The finding will stimulate future exploration of magnetic ferroaxial materials. | | | | | | Editors' Suggestion Liu Yang, Alejandro A. Jara, Zheng Duan, Andrew Smith, Brian Youngblood, Rodrigo E. Arias, and Ilya N. Krivorotov Phys. Rev. B 106, 144410 (2022) – Published 10 October 2022  | Edge magnons play a key role in the magnetization reversal of ferromagnetic nanoelements and may find applications in the field of magnonics. The authors tune the parametric excitation of edge magnons in ferromagnetic nanowires by spin Hall torque in order to probe the magnon ellipticity. The study reveals that the edge magnon ellipticity is significantly lower than that predicted by a simple model of the magnetic edge. This work presents a sensitive probe of magnetic properties at nanoelement edges. | | | | | | Editors' Suggestion Dmitriy Zusin et al. Phys. Rev. B 106, 144422 (2022) – Published 19 October 2022  | Ultrafast control of magnetism holds great promise for novel and efficient high-speed microelectronic devices. This includes manipulation of the domain walls that separate magnetic domains. Surprisingly, by use of a free-electron x-ray laser, the authors discover here that femtosecond laser pumping of a multidomain sample causes the domain walls to broaden from 29 to 51 nm in less than 1.6 picoseconds. They also find intriguing evidence of a simultaneous spatial rearrangement of domains. These unexpected results open new avenues for ultrafast optical manipulation of magnetism. | | | | | | Editors' Suggestion Kexin Feng, Aysel Shiralieva, and Natalia B. Perkins Phys. Rev. B 106, 144424 (2022) – Published 20 October 2022  | Here, the authors propose that phonon dynamics can be exploited to look for the signatures of fractionalization in three-dimensional Kitaev spin liquids. Motivated by recent studies of the hyperhoneycomb Kitaev material β-Li2IrO3, they compute the sound attenuation in the spin-phonon coupled Kitaev model on the hyperhoneycomb lattice, in which Majorana fermions have nodal-line band structure. They show that at low temperatures its angular dependence displays a characteristic pattern, which opens the possibility of detecting the proximity to the Kitaev spin liquid phase in this compound in ultrasound experiments. | | | | | | Editors' Suggestion Takuro Sato, Wataru Koshibae, Akiko Kikkawa, Yasujiro Taguchi, Naoto Nagaosa, Yoshinori Tokura, and Fumitaka Kagawa Phys. Rev. B 106, 144425 (2022) – Published 21 October 2022  | Whether a nonthermodynamic driving force, such as an electric current, can induce a global change like a thermodynamic phase transition of the whole system remains an open question. Here, the authors report on a current-driven skyrmion-to-nonskyrmion transition, detected both experimentally and numerically by targeting microscaled MnSi. This nonequilibrium phase change by current emerges when the system is spatially confined by an open boundary, suggesting that a range of novel nonequilibrium phenomena can be explored with attention to system size. | | | | | | Editors' Suggestion Reza Rouzegar, Liane Brandt, Lukáš Nádvorník, David A. Reiss, Alexander L. Chekhov, Oliver Gueckstock, Chihun In, Martin Wolf, Tom S. Seifert, Piet W. Brouwer, Georg Woltersdorf, and Tobias Kampfrath Phys. Rev. B 106, 144427 (2022) – Published 24 October 2022  | The authors observe here that (a) laser-induced ultrafast demagnetization (UDM) of a metallic ferromagnet F has the same time evolution as (b) terahertz spin transport (TST) from F into an adjacent normal metal N. They conclude that UDM in F and TST in F|N samples are driven by the same force: (c) a generalized spin voltage, i.e., an excess magnetization of F. One can now apply the vast knowledge of UDM to TST to significantly increase spin-current amplitudes for ultrafast spintronic applications. | | | | | | Editors' Suggestion A. Zelenskiy, T. L. Monchesky, M. L. Plumer, and B. W. Southern Phys. Rev. B 106, 144433 (2022) – Published 26 October 2022  | Magnetic compounds that combine the effects of geometric frustration and strong spin-orbit coupling (SOC) often host exotic magnetic phases. In many cases, anisotropic lattice-dependent interactions that originate from the SOC significantly reduce the symmetry of the system and constrain the magnetic moments to specific orientations. Using numerical simulations and symmetry analysis, this study demonstrates that, in compounds with the AB-stacked kagome layer structure, the anisotropy gives rise to a large number of duality transformations that provide exact mappings between the properties of distinct magnetic phases. | | | | | | Jessica Thomas and Michael Thoennessen Phys. Rev. B 106, 150001 (2022) – Published 11 October 2022 | | | Editors' Suggestion Peru d'Ornellas, Ryan Barnett, and Derek K. K. Lee Phys. Rev. B 106, 155124 (2022) – Published 13 October 2022  | Chern insulators display a remarkable insensitivity to spatial disorder and imperfections. Despite this, the Chern number itself is defined in momentum space, and can only be calculated in a clean crystalline material. The authors propose here a spatial Chern marker defined on physical grounds – as the local cross-conductivity around a chosen point in the bulk of the system. The formulation can be related to several other proposed local measures but has the advantage that it constitutes a physical observable of the system. Examples are probed, showing that it is quantized when calculated sufficiently far from the boundary and resistant against disorder. | | | | | | Editors' Suggestion Artem V. Tarasov, Daria Glazkova, Susanne Schulz, Georg Poelchen, Kristin Kliemt, Alexej Kraiker, Matthias Muntwiler, Clemens Laubschat, Alexander Generalov, Craig Polley, Cornelius Krellner, Denis V. Vyalikh, and Dmitry Yu. Usachov Phys. Rev. B 106, 155136 (2022) – Published 19 October 2022  | By means of 4f photoemission measurements and first-principles calculations, the authors demonstrate here how the crystal electric field (CEF) and related magnetic properties can be modified at the surface of rare-earth materials. For TbRh2Si2, CEF at the Tb surface makes the 4f moments orthogonal to those in the bulk. For the Tb layer below the Si termination, the temperature-dependent photoemission data reveal larger CEF splitting relative to the bulk. The methodology used here can facilitate unveiling of the surface magnetic properties of layered 4f systems. | | | | | | Editors' Suggestion Tomáš Bzdušek and Joseph Maciejko Phys. Rev. B 106, 155146 (2022) – Published 24 October 2022  | Hopping models on geometrically frustrated lattices, such as the kagome and dice lattices, exhibit perfectly flat energy bands that result from eigenstates localized along contractible and/or noncontractible real-space loops. The degeneracy of such flat bands has been understood from an interplay of real-space topology and momentum-space band theory. Here, the authors generalize this paradigm to frustrated hyperbolic lattices, including those realized in recent circuit quantum electrodynamics experiments. They show that hyperbolic flat-band characteristics can similarly be understood by combining real-space topology arguments with the recently developed hyperbolic band theory. | | | | | | Editors' Suggestion Robert J. Anderson, Charles J. C. Scott, and George H. Booth Phys. Rev. B 106, 155158 (2022) – Published 31 October 2022  | When electrons interact not only with themselves, but also with bosons (phonons or other bosonic quasiparticles), what was previously a "curse of dimensionality" for its computational solution now becomes one of infinite size. To deal with this, the authors adapt here a recent method for its stochastic solution, without requiring truncation of the bosonic occupations, and which allows systematic improvability to exact solutions. They apply this to the paradigmatic Hubbard-Holstein model of local phonons, finding a state-of-the-art solution in the thermodynamic limit, as well as to a novel approach in which long-range collective electronic fluctuations are mapped to bosonic quasiparticles to tackle even long-range interacting problems of purely electronic form. | | | | | | Editors' Suggestion Seongjin Ahn and Sankar Das Sarma Phys. Rev. B 106, 155427 (2022) – Published 27 October 2022  | The low-temperature resistivity and the temperature-dependent inelastic scattering rate of several different doped 2D semiconductor systems are described and discussed from the perspective of the Planckian hypothesis of the scattering rate having an intrinsic fundamental bound of kBT. The Planckian holds for all the systems with the scattering rate never exceeding kBT by more than an order of magnitude either in the experiment or in the theory. In addition, the authors calculate the temperature-dependent electron-electron inelastic scattering rate by obtaining the temperature-dependent self-energy arising from the Coulomb interaction, also finding it to obey the Planckian bound within an order of magnitude at all densities and temperatures. A theory is provided for why such a generalized Planckian bound applies generically. | | | | | | Editors' Suggestion F. A. Calderon-Vargas, Edwin Barnes, and Sophia E. Economou Phys. Rev. B 106, 165302 (2022) – Published 10 October 2022  | Flip-flop qubits, encoded in the antiparallel spin states of electron and nuclear spins in phosphorus donors in silicon, are promising for quantum processors due to their long coherence times, long-range two-qubit coupling, and CMOS compatibility. However, the large Hilbert space complicates understanding and controlling the dynamics. In this work, the authors use sophisticated techniques to derive effective flip-flop qubit Hamiltonians and design optimal control pulses that implement high-fidelity single-qubit gates that are much faster and more robust than previous proposals. | | | | | | Editors' Suggestion Letter K. L. Seyler, A. Ron, D. Van Beveren, C. R. Rotundu, Y. S. Lee, and D. Hsieh Phys. Rev. B 106, L140403 (2022) – Published 12 October 2022  | The mesoscopic magnetism of undoped cuprates is not well studied because the antiferromagnetic states and domain walls are difficult to locally detect. The authors overcome this challenge using optical second-harmonic generation on the cuprate Sr2Cu3O4Cl2, allowing direct visualization of the antiferromagnetic microstructure. They discover an unusual 90° domain reorientation transition, which enables deterministic antiferromagnetic switching and causes a divergent domain wall susceptibility that generates sample-sized single-domain antiferromagnetic states. | | | | | | Editors' Suggestion Letter Yizhi You, Elisabeth Wybo, Frank Pollmann, and S. L. Sondhi Phys. Rev. B 106, L161104 (2022) – Published 10 October 2022  | The quantum entanglement of a wave function generates the information entropy carried by each qubit of the many-body system and correspondingly creates unique quantum matter. In this work, the authors attempt to visualize distinct quasiparticles and collective motions from an entanglement perspective. Remarkably, many salient features of the quasiparticles, including their quantum numbers, locality, and fractionalization, are reflected in the entanglement spectrum and in the mutual information. | | | | | | Editors' Suggestion Letter M. O. Ajeesh, S. M. Thomas, S. K. Kushwaha, E. D. Bauer, F. Ronning, J. D. Thompson, N. Harrison, and P. F. S. Rosa Phys. Rev. B 106, L161105 (2022) – Published 10 October 2022  | Noncentrosymmetric Ce3Bi4Pd3 has recently attracted tremendous attention as a strongly correlated topological semimetal candidate. Conflicting experimental results, however, argue for either a Weyl Kondo semimetallic or a narrow-gap Kondo insulating ground state. Using electrical transport measurements on bulk crystals and microstructure devices under hydrostatic pressure, the authors show that Ce3Bi4Pd3 exhibits a narrow-gap Kondo insulating ground state. The results provide important evidence for the ground state of a sought-after Weyl Kondo semimetal candidate and shed light on the experimental and theoretical search for strongly correlated topological materials. | | | | | | Editors' Suggestion Letter Thivan M. Gunawardana and Berislav Buča Phys. Rev. B 106, L161111 (2022) – Published 21 October 2022  | Stark many-body localization (MBL) occurs when interacting quantum particles are placed in a strong linear field gradient. Localization of excitations, coherent Bloch oscillations, Hilbert-space fragmentation, and scarring have been observed numerically and experimentally, but their origin is not understood. The authors explain these features analytically by perturbatively constructing an algebraic structure of Stark MBL Hamiltonians they name "dynamical l-bits". These structures are exponentially stable in the field gradient strength. Thus, the work has potential implications for quantum information processing. | | | | | | | |
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