Advanced Physics Research最新文献

Graphene has a long spin lifetime and hyperfine interactions, favoring its potential application as spintronics. Despite the recent discoveries of spin-containing graphene materials, graphene-based materials with room-temperature macroscopic ferromagnetism are extremely rare. In this article, room-temperature ferromagnetic amorphous graphene oxide (GO) is synthesized by introducing abundant oxygen-containing functional groups and C defects into single-layered graphene, followed by a self-assembly process under supercritical CO₂ (SC CO₂). Such amorphous GO exhibits the highest saturation magnetization (1.71 emu g⁻¹) and remanent magnetization (0.251 emu g⁻¹) compared to the rest of metal-free graphene-based materials at room temperature. Experimental and theoretical investigations attribute such strong ferromagnetism to the bridging of the adjacent graphene layers though the out-of-plane oxygen-containing groups, which leads to asymmetric lattices with large net magnetic moments.

In magnetic insulators, the sense of rotation of the magnetization is associated with novel phases of matter and exotic transport phenomena. Aimed to find new sources of chiral magnetism rooted in intrinsic fields and geometry, twisted square bilayers of magnetic dipoles with easy plane anisotropy are studied. For no twist, each lattice settles in the zig-zag magnetic state and orders antiferromagnetically to the other layer. The moire patterns that result from the mutual rotation of the two square lattices influence such zig-zag order, giving rise to several phases that depict non-collinear magnetic textures with chiral motifs that break both time and inversion symmetry. For certain moire angles, helical and toroidal magnetic orders arise. Changing the vertical distance between layers can further manipulate these novel phases. It is shown that the dipolar interlayer interaction induces an emergent twist-dependent chiral magnetic field orthogonal to the direction of the zig-zag chains, which is responsible for the internal torques conjugated to the toroidal orders.

Vanadyl(IV) 5,10,15,20-tetraphenylporphyrin (VOTPP) is an S = 1/2 molecular system with remarkable spin qubit properties. Its structure offers a higher chemical tunability with respect to archetypal molecular qubits, such as vanadyl(IV)Phthalocyanines (VOPc), and a less rigid organic scaffold where peripheral phenyl rings can promote electron decoupling from the substrate. The properties of a VOTPP monolayer on the Ag(100) surface by photoemission spectroscopies and synchrotron radiation are studied. The results indicate that the electronic and spin features of the massive phase are retained in the monolayer. Moreover, X-ray photoelectron spectroscopy revealed the existence of two distinct species characterized by varying strengths of molecule-surface interactions. Like VOPc, these species can be assigned to molecules with the vanadyl group oriented upward or toward the surface. However, in contrast to VOPc, only subtle screening effects are observed in the oxygen-down configuration, suggesting a more pronounced decoupling effect inherent in the VOTPP structure. This opens broader perspectives for investigations focusing on spin characteristics at the single-molecule level.

Entangled Two-Photon Absorption

The front cover illustrates the fluorescence excitation of quantum dot molecules by absorption of entangled photon pairs. The so-called entangled two-photon absorption is highly affected by the generation of these photon pairs. In article number 2300037, Tobias Bernd Gäbler and co-workers describe the important properties of an ultra-bright photon pair source based on nonlinear waveguides and its usage to approach fluorescence excitation. (Image designed by Christian Süß).

Wurtzite-type Al_1−xSc_xN solid solutions grown by metal organic chemical vapor deposition are for the first time confirmed to be ferroelectric. The film with 230 nm thickness and x = 0.15 exhibits a coercive field of 5.5 MV cm⁻¹ at a measurement frequency of 1.5 kHz. The single crystal quality and homogeneous chemical composition of the film are confirmed by X-ray diffraction and spectroscopic methods such as time of flight secondary ion mass spectrometry. Annular bright field scanning transmission electron microscopy serves to prove the ferroelectric polarization inversion at the unit cell level. The single crystal quality further allows to image the large-scale domain pattern of a wurtzite-type ferroelectric for the first time, revealing a predominantly cone-like domain shape along the c-axis of the material. As in previous work, this again implies the presence of strong polarization discontinuities along this crystallographic axis, which can be suitable for current transport. The domains are separated by narrow domain walls, for which an upper thickness limit of 3 nm is deduced but which can potentially be atomically sharp. The authors are confident that these results will advance the commencement of the integration of wurtzite-type ferroelectrics to GaN as well as generally III-N-based heterostructures and devices.

In December 2022, the open-access journal Advanced Physics Research (APXR) celebrated an important milestone—the first issue was published. This new platform aims to publish papers covering the whole gamut of physics, from applied to fundamental, with a strong emphasis on important and relevant current topics, such as condensed matter physics, materials physics, semiconductor physics, etc.

Although only one year old, the journal has achieved a unique role among physics publishing platforms as a new home for excellent results; up to now, 137 articles have been accepted, including Research Articles, Reviews, and Perspectives. Among these, the new journal has published its first article by a Nobel Laureate, “Time-Resolved Photoemission Electron Microscopy on a ZnO Surface Using an Extreme Ultraviolet Attosecond Pulse Pair”, DOI 10.1002/apxr.202300122 by Anne L'Huillier and co-authors. Moreover, topical special issues on Topological Physics, guest-edited by Xiaotian Wang and Gang Zhang; Surface-Enhanced Raman Spectroscopy (SERS), guest-edited by Ramon Angel Alvarez Puebla and Xing Yi Ling; Quantum Anomalies, guest-edited by Michael Thompson Pettes and Avadh Behari Saxena; and Magnetic Materials, guest-edited by Marco Berritta and Joseph Barker, are ongoing.

Advanced Physics Research serves the whole needs and entire interests of the physics community. The journal offers free format submission for a fast and simple submission process, please see the Author Guidelines for more information. The peer-review process involves highly personalized communication among authors, reviewers, and editors. Frequently specific and tough questions are posed to authors, and they need to be open to significant changes of their work. These efficient, insightful, and fruitful exchanges facilitate great articles in the end. Many thanks to the numerous experts who devote considerable and valuable time to maintaining the high quality of the papers. The most accessed articles are listed here to broadcast journal topics and to further improve article visibility.

The journal has not only been intensely supported by authors and reviewers but also by the Editorial Advisory Board members, who help make decisions on difficult cases such as appeals. The board members provide timely and informal advice on the journal's scope and strategy and sometimes also serve as ambassadors for the journal. The cooperation among different roles ensures that the journal runs well. We say thank you to everyone who has contributed to the success of Advanced Physics Research.

Advanced Physics Research is promoting an inclusive open communication platform for connecting readers, authors, reviewers, editors, and board members with the content and tools they need, which leads Advanced Physics Research to be an excellent home for articles with publication based on scientific merit alone. The open access publication model is undoubtedly benefit

Antiferromagnetic Spintronics

Energy efficient and fast, non-volatile memory is the apogee of antiferromagnetic spintronics. The cover page shows a device which utilizes an antiferromagnetic, B-doped thin film of magnetoelectric Cr₂O₃. Voltage applied across the film controls its Néel vector and state variable. To facilitate high temperature operation, the Néel temperature, T_N, of B:Cr₂O₃ is tuned. In article 2300061 by Ather Mahmood, Christian Binek, and colleagues, cold neutron and x-ray photoemission (XPS) data show that annealing leads to interfacial B-accumulation and T_N increase. Neutron and XPS depth profiling map the depth dependent B-concentration.

Spontaneous electric polarization is recently observed in multilayered van der Waals stacked materials, arising from a symmetry breaking in a unit cell with two or more constituent species, or non-centrosymmetric intra-layer atom displacement in single-atom-species materials. Here, it is shown that even elemental crystals, consisting of one type of atom and composed of non-polar and centrosymmetric layers, exhibit electric polarization if arranged in an appropriate three-dimensional  architecture. This concept is demonstrated here for mixed-stacking tetra-layer polytypes of non-polar graphene sheets. Surprisingly, it is find that the room temperature out-of-plane electric polarization increases with external electrostatic hole doping, rather than decreases with it owing to screening. Using first-principles calculations, as well as a self-consistent tight-binding model, the emergence of polarization is explain in terms of inter-layer charge rearrangement and the doping dependence in terms of gating-induced inter-layer charge transfer. This newly discovered intrinsic polarization may therefore offer new venues for designing the electronic response of graphene-based polytypes to external fields.