Physical Review B最新文献

{"title":"Coexistence of antiferromagnetism and ferrimagnetism in adjacent honeycomb layers","authors":"D. Szaller, L. Prodan, K. Geirhos, V. Felea, Y. Skourski, D. Gorbunov, T. Förster, T. Helm, T. Nomura, A. Miyata, S. Zherlitsyn, J. Wosnitza, A. A. Tsirlin, V. Tsurkan, I. Kézsmárki","doi":"10.1103/physrevb.111.184404","DOIUrl":"https://doi.org/10.1103/physrevb.111.184404","url":null,"abstract":"Ferro-/ferri- and antiferromagnetically ordered phases are typically exclusive in nature, thus, their coexistence in atomic-scale proximity is expected only in heterostructures. Breaking this paradigm and broadening the range of unconventional magnetic states, we report here on the observation of a new, atomic-scale hybrid spin state. This ordering is stabilized in three-dimensional crystals of the polar antiferromagnet Co</a:mi>2</a:mn></a:msub>Mo</a:mi>3</a:mn></a:msub>O</a:mi>8</a:mn></a:msub></a:mrow></a:math> by magnetic fields applied perpendicular to the Co honeycomb layers and possesses a spontaneous in-plane ferromagnetic moment. Our microscopic spin model, capturing the observed field dependence of the longitudinal and transverse magnetization as well as the magnetoelectric/elastic properties, reveals that this novel spin state is composed of an alternating stacking of antiferromagnetic and ferrimagnetic honeycomb layers. The strong intralayer and the weak interlayer exchange couplings together with competing anisotropies at octahedral and tetrahedral Co sites are identified as the key ingredients to stabilize antiferromagnetic and ferrimagnetic layers in such close proximity. We show that the proper balance of magnetic interactions can extend the stability range of this hybrid phase down to zero magnetic field. The possibility to realize a layer-by-layer stacking of such distinct spin orders via suitable combinations of microscopic interactions opens a new dimension toward the nanoscale engineering of magnetic states. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":"96 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143901210","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Operator spreading in random unitary circuits with unitary-invariant gate distributions","authors":"Zhiyang Tan, Piet W. Brouwer","doi":"10.1103/physrevb.111.184301","DOIUrl":"https://doi.org/10.1103/physrevb.111.184301","url":null,"abstract":"Random unitary circuits have become a model system to investigate information scrambling in quantum systems. In the literature, mostly random circuits with Haar-distributed gate operations have been considered. In this work, we investigate operator spreading in random unitary circuits in which the elementary gate operations are drawn from general unitary-invariant ensembles, which include the well-studied Haar-distributed random unitary circuits as a special case. Similar to the Haar-distributed case, the long-time behavior of operator spreading with the more general unitary-invariant gate distribution is governed by drift-diffusion equations characterized by the butterfly velocity v</a:mi>B</a:mi></a:msub></a:math> and a diffusion constant <c:math xmlns:c=\"http://www.w3.org/1998/Math/MathML\"><c:mi mathvariant=\"script\">D</c:mi></c:math>. Differences with the Haar-random case are (i) that it takes a finite time <e:math xmlns:e=\"http://www.w3.org/1998/Math/MathML\"><e:msub><e:mi>τ</e:mi><e:mi mathvariant=\"normal\">b</e:mi></e:msub></e:math> until ensemble-averaged Pauli-string weights take a “binary” form, in which they depend only on whether Pauli operators inside the support of the Pauli strong are equal to the identity matrix, and (ii) that the operator spreading is characterized by a finite “domain-wall width” <g:math xmlns:g=\"http://www.w3.org/1998/Math/MathML\"><g:msub><g:mi>n</g:mi><g:mi>DW</g:mi></g:msub></g:math> separating regions with a random-matrix-like Pauli-string distribution. To illustrate these findings, we perform explicit calculations for random unitary circuits distributed according to the Poisson kernel, which interpolates between the trivial and Haar-distributed circuits. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":"89 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143897839","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bulk band structure of RuO2 measured with soft x-ray angle-resolved photoemission spectroscopy","authors":"Zihan Lin, Dong Chen, Wenlong Lu, Xin Liang, Shiyu Feng, Kohei Yamagami, Jacek Osiecki, Mats Leandersson, Balasubramanian Thiagarajan, Junwei Liu, Claudia Felser, Junzhang Ma","doi":"10.1103/physrevb.111.134450","DOIUrl":"https://doi.org/10.1103/physrevb.111.134450","url":null,"abstract":"Altermagnetism exhibits unique physical properties such as spin-momentum locking, anomalous Hall effect, nontrivial topological phase, and giant magnetoresistance. Among all the predicted candidates, several room-temperature altermagnets are suggested to host significant potential applications. Ru</a:mi>O</a:mi>2</a:mn></a:msub></a:mrow></a:math> has been proposed as the most promising candidate. However, recently, there is intense debate about whether <c:math xmlns:c=\"http://www.w3.org/1998/Math/MathML\"><c:mrow><c:mi>Ru</c:mi><c:msub><c:mi mathvariant=\"normal\">O</c:mi><c:mn>2</c:mn></c:msub></c:mrow></c:math> exhibits magnetic order or not. Experiments by several different technologies claim the collinear magnetic order and spin-splitting-induced effects. However, very recent muon spin resonance (μSR) results reveal no magnetic order in <e:math xmlns:e=\"http://www.w3.org/1998/Math/MathML\"><e:mrow><e:mi>Ru</e:mi><e:msub><e:mi mathvariant=\"normal\">O</e:mi><e:mn>2</e:mn></e:msub></e:mrow></e:math>, which indicates that the time-reversal symmetry is not broken. Direct observation of the high-resolution bulk band structure is absent to date but essential to investigate the electronic structure of <g:math xmlns:g=\"http://www.w3.org/1998/Math/MathML\"><g:mrow><g:mi>Ru</g:mi><g:msub><g:mi mathvariant=\"normal\">O</g:mi><g:mn>2</g:mn></g:msub></g:mrow></g:math>. In this study, utilizing soft x-ray angle-resolved photoemission spectroscopy, we report systematic direct experimental observation of bulk band structure of <i:math xmlns:i=\"http://www.w3.org/1998/Math/MathML\"><i:mrow><i:mi>Ru</i:mi><i:msub><i:mi mathvariant=\"normal\">O</i:mi><i:mn>2</i:mn></i:msub></i:mrow></i:math>. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":"21 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143897835","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tunable enhancement of magnetization dynamics by selection of the crystallographic orientation of the hybrid interface of exchange-coupled α−Fe2O3 /permalloy heterostructures","authors":"Hassan Al-Hamdo, Tobias Wagner, Philipp Schwenke, Gutenberg Kendzo, Maximilian Dausend, Laura Scheuer, Misbah Yaqoob, Vitaliy I. Vasyuchka, Philipp Pirro, Olena Gomonay, Mathias Weiler","doi":"10.1103/physrevb.111.l180401","DOIUrl":"https://doi.org/10.1103/physrevb.111.l180401","url":null,"abstract":"We investigate spin dynamics in α</a:mi>−</a:mtext>Fe</a:mi>2</a:mn></a:msub>O</a:mi>3</a:mn></a:msub>/</a:mo>Ni</a:mi>80</a:mn></a:msub>Fe</a:mi>20</a:mn></a:msub></a:mrow></a:math> (Py) heterostructures, uncovering a robust mechanism for designing the ferromagnetic resonance (FMR) frequency through control of crystal orientation, temperature, and applied magnetic field. Employing cryogenic ferromagnetic resonance spectroscopy, we demonstrate that the relative orientation of the Néel vector of <c:math xmlns:c=\"http://www.w3.org/1998/Math/MathML\"><c:mrow><c:mi>α</c:mi><c:mtext>−</c:mtext><c:msub><c:mi>Fe</c:mi><c:mn>2</c:mn></c:msub><c:msub><c:mi mathvariant=\"normal\">O</c:mi><c:mn>3</c:mn></c:msub></c:mrow></c:math> and the magnetization of the Py layer is highly tunable across the Morin transition temperature (<e:math xmlns:e=\"http://www.w3.org/1998/Math/MathML\"><e:msub><e:mi>T</e:mi><e:mtext>M</e:mtext></e:msub></e:math>). Central to our findings is the pivotal role of crystal orientation in governing the spin dynamics, with the reorientation of the Néel vector serving as a complementary mechanism that further modulates the system's behavior. Our experiments and corroborating theoretical model reveal distinct resonance behavior for different crystal orientations, highlighting the pivotal role of the mutual Néel vector and magnetization geometry in dictating FMR frequencies. In this way, we can tune the FMR frequencies up to a tenfold increase by manipulating the mutual Néel vector/magnetization configuration. Our study comprises all common <f:math xmlns:f=\"http://www.w3.org/1998/Math/MathML\"><f:mrow><f:mi>α</f:mi><f:mtext>−</f:mtext><f:msub><f:mi>Fe</f:mi><f:mn>2</f:mn></f:msub><f:msub><f:mi mathvariant=\"normal\">O</f:mi><f:mn>3</f:mn></f:msub></f:mrow></f:math> crystal orientations and develops a unified theoretical description of the ensuing spin dynamics. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":"9 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143897710","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fermi surfaces of the nodal-line candidates CaCdGe and CaCdSn: Discrepancy between band structure calculations and quantum oscillation measurements","authors":"B. V. Schwarze, F. Husstedt, P. Chekhonin, S. Galeski, T. Helm, J. Liu, Yu. Prots, T. Romanova, M. Uhlarz, M. v. Zimmermann, D. Kaczorowski, J. Wosnitza","doi":"10.1103/physrevb.111.155154","DOIUrl":"https://doi.org/10.1103/physrevb.111.155154","url":null,"abstract":"Nodal-line semimetals are characterized by one-dimensional lines or loops of topologically protected band-touching nodes. For two recent nodal-line semimetal candidates, CaCdGe and CaCdSn, band structure calculations show nontopological and topological valence bands with the nodal band crossings above the Fermi level. Here, we present our investigation of the Fermi surfaces of CaCdGe and CaCdSn by use of de Haas–van Alphen measurements and band structure calculations. Our measurements reveal many quantum oscillation frequencies that are not predicted by calculations. This discrepancy casts doubt on the calculated band structures and, thus, on the precise nature of the topology of these systems. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":"1 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143897711","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Trap-assisted Auger-Meitner recombination in GaN p-i-n diodes","authors":"Tanay Tak, Wan Ying Ho, Iris Celupica-Liu, Yi Chao Chow, Jacques Peretti, Claude Weisbuch, James S. Speck","doi":"10.1103/physrevb.111.155308","DOIUrl":"https://doi.org/10.1103/physrevb.111.155308","url":null,"abstract":"Most properties of semiconductor devices are dominated by shallow impurities. However, deep defects often play an important role, for instance, in recombination processes or high field transport. While a variety of techniques are available to assess the density and energy levels of impurities, other properties, such as the recombination mechanisms of the defects, escape observation. We report on the direct measurement of hot electrons generated by trap-assisted Auger-Meitner recombination (TAAR) in GaN diodes. By performing electron emission spectroscopy (EES) on diodes with surfaces activated to negative electron affinity by cesium, we observe the expected overflow electrons of diodes under low current injection. However, when operating the devices at higher current densities, as low as ∼25 A/c</a:mi>m</a:mi></a:mrow>2</a:mn></a:msup></a:mrow></a:math>, we measure the emission of high-energy electrons. At variance with the observed hot electrons in light-emitting diodes (LEDs) using EES, the hot electrons generated in diodes at our tested currents cannot be from Auger-Meitner recombination due to the diodes' significantly lower carrier densities compared to those in LEDs. During our measurements, we observe the emission of accumulated electrons with energies ∼0.42 eV, ∼0.99 eV, ∼1.43 eV, and ∼2.32 eV above the conduction-band minimum (CBM) at various bias conditions, suggesting the existence of conduction-band features in GaN at these energies where electrons can be long-lived, such as satellite-valley minima and inflection points. We also measure incompletely relaxed hot electrons approaching energies 1.97 ± 0.13 eV and 2.94 ± 0.13 eV above the CBM, as the diodes are biased to high currents, suggesting at least some of the TAAR partaking defects have an energy level <d:math xmlns:d=\"http://www.w3.org/1998/Math/MathML\"><d:mo>≳</d:mo><d:mn>1.97</d:mn></d:math> eV and <e:math xmlns:e=\"http://www.w3.org/1998/Math/MathML\"><e:mo>≳</e:mo><e:mn>2.94</e:mn></e:math> eV away from either the conduction or valence band edges. Additionally, at our highest operating currents, we measure hot electrons with energies 3.28 ± 0.13 eV above the CBM, providing direct evidence of TAAR processes involving shallow impurities. This unexpected observation of TAAR in GaN diodes spotlights the importance of further studies of defects in GaN and the necessity to incorporate the multi-phonon emission, radiative, and TAAR capture steps of defect-assisted recombination cycles into device modeling. Furthermore, this experiment demonstrates the applicability of the simplest semiconductor structures, diodes, as a test bed to study the rich recombination physics of semiconductor materials. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":"7 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143897485","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Robustness of electron charge shuttling: Architectures, pulses, charge defects, and noise thresholds","authors":"Minjun Jeon, Simon C. Benjamin, Andrew J. Fisher","doi":"10.1103/physrevb.111.195302","DOIUrl":"https://doi.org/10.1103/physrevb.111.195302","url":null,"abstract":"In semiconductor-based quantum technologies, the capability to shuttle charges between components is profoundly enabling. We numerically simulated various “conveyor-belt” shuttling scenarios for simple Si</a:mi>/</a:mo>SiO</a:mi>2</a:mn></a:msub></a:mrow></a:math> devices, explicitly modeling the electron's wave function using grid-based split-operator methods and a time-dependent 2D potential (obtained from a Poisson solver). This allowed us to fully characterize the electron loss probability and excitation fraction. Remarkably, with as few as three independent electrodes, the process can remain near-perfectly adiabatic even in the presence of pulse imperfection, nearby charge defects, and Johnson-Nyquist noise. Only a substantial density of charge defects, or defects at “adversarial” locations, can catastrophically disrupt the charge shuttling. While we do not explicitly model the spin or valley degrees of freedom, our results from this charge propagation study support the conclusion that conveyor-belt shuttling is an excellent candidate for providing connectivity in semiconductor quantum devices. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":"3 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143897836","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Competing charge density wave phases in YNiC2","authors":"Marta Roman, Simone Di Cataldo, Berthold Stöger, Lisa Reisinger, Emilie Morineau, Kamil K. Kolincio, Herwig Michor","doi":"10.1103/physrevb.111.195101","DOIUrl":"https://doi.org/10.1103/physrevb.111.195101","url":null,"abstract":"Charge density wave (CDW) orders in YNiC</a:mi>2</a:mn></a:msub></a:math> are studied by means of combined experimental and computational techniques. On the experimental side, single crystals grown by the floating-zone method were examined by means of x-ray diffraction, as well as transport and thermal techniques. Density functional theory (DFT) calculations founded on the experimentally determined parent and CDW-modified crystal structures provide details of electronic and phononic structures as well as electron-phonon coupling and resolve changes inflicted upon entering the different CDW phases. Thereby, contrasting effects of subsequently emerging CDW states characterized by incommensurate <b:math xmlns:b=\"http://www.w3.org/1998/Math/MathML\"><b:msub><b:mi>q</b:mi><b:mrow><b:mn>1</b:mn><b:mtext>ic</b:mtext></b:mrow></b:msub></b:math> and commensurate <c:math xmlns:c=\"http://www.w3.org/1998/Math/MathML\"><c:msub><c:mi>q</c:mi><c:mrow><c:mn>2</c:mn><c:mtext>c</c:mtext></c:mrow></c:msub></c:math> modulation vectors are revealed. The former state, on-setting below <d:math xmlns:d=\"http://www.w3.org/1998/Math/MathML\"><d:mrow><d:msub><d:mi>T</d:mi><d:mtext>1ic</d:mtext></d:msub><d:mo>≃</d:mo><d:mn>305</d:mn><d:mspace width=\"0.16em\"/><d:mi mathvariant=\"normal\">K</d:mi></d:mrow></d:math>, weakly modifies the electronic structure by opening an almost isotropic gap on a minor part of the Fermi surface (FS). The latter phase, which takes over below <g:math xmlns:g=\"http://www.w3.org/1998/Math/MathML\"><g:mrow><g:msub><g:mi>T</g:mi><g:mtext>2c</g:mtext></g:msub><g:mo>≃</g:mo><g:mn>272</g:mn><g:mspace width=\"0.16em\"/><g:mi mathvariant=\"normal\">K</g:mi></g:mrow></g:math> has a more pronounced impact on physical properties via a decomposition of larger parts of the FS. These dissimilar behaviors are directly reflected in the electronic transport anisotropy, which is significantly weakened in the <j:math xmlns:j=\"http://www.w3.org/1998/Math/MathML\"><j:msub><j:mi>q</j:mi><j:mrow><j:mn>2</j:mn><j:mtext>c</j:mtext></j:mrow></j:msub></j:math>-type CDW state. As revealed by our DFT studies, CDW phases are very close in energy and their origin is directly related to the anisotropy of electron-phonon coupling, which is linked to a specific orbital character of related FS sheets. Specific heat and thermal expansion studies reveal a nearly reversible first-order phase transition at around <k:math xmlns:k=\"http://www.w3.org/1998/Math/MathML\"><k:mrow><k:msub><k:mi>T</k:mi><k:mtext>2c</k:mtext></k:msub><k:mo>≃</k:mo><k:mn>272</k:mn><k:mspace width=\"0.16em\"/><k:mi mathvariant=\"normal\">K</k:mi></k:mrow></k:math>, where both CDW phases coexist within a <n:math xmlns:n=\"http://www.w3.org/1998/Math/MathML\"><n:mi>T</n:mi></n:math> interval of about 10 K. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":"56 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143897837","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"First-principles investigation of magnetic exchange force microscopy on adatoms adsorbed on an antiferromagnetic surface","authors":"Soumyajyoti Haldar, Stefan Heinze","doi":"10.1103/physrevb.111.134447","DOIUrl":"https://doi.org/10.1103/physrevb.111.134447","url":null,"abstract":"Using density functional theory (DFT), we calculate the magnetic short-ranged exchange forces between a magnetic tip and an adatom adsorbed on the antiferromagnetic Mn monolayer on the W(110) surface [Mn/W(110)]. These exchange forces can be measured in magnetic exchange force microscopy allowing atomic-scale imaging of spin structures on insulating and conducting surfaces. We consider two types of 3&lt;/a:mn&gt;d&lt;/a:mi&gt;&lt;/a:mrow&gt;&lt;/a:math&gt; transition-metal atoms with intrinsic magnetic moments: Co and Mn and Ir as an example of a &lt;b:math xmlns:b=\"http://www.w3.org/1998/Math/MathML\"&gt;&lt;b:mrow&gt;&lt;b:mn&gt;5&lt;/b:mn&gt;&lt;b:mi&gt;d&lt;/b:mi&gt;&lt;/b:mrow&gt;&lt;/b:math&gt; transition-metal atom exhibiting an induced magnetic moment on Mn/W(110). The tips are modeled by Fe pyramids and terminated either with an Fe or a Mn apex atom. From our total energy DFT calculations for a parallel and antiparallel alignment between tip and adatom magnetic moments we obtain the exchange energy &lt;c:math xmlns:c=\"http://www.w3.org/1998/Math/MathML\"&gt;&lt;c:mrow&gt;&lt;c:msub&gt;&lt;c:mi&gt;E&lt;/c:mi&gt;&lt;c:mi&gt;ex&lt;/c:mi&gt;&lt;/c:msub&gt;&lt;c:mrow&gt;&lt;c:mo&gt;(&lt;/c:mo&gt;&lt;c:mi&gt;d&lt;/c:mi&gt;&lt;c:mo&gt;)&lt;/c:mo&gt;&lt;/c:mrow&gt;&lt;/c:mrow&gt;&lt;/c:math&gt; as a function of tip-adatom distance &lt;d:math xmlns:d=\"http://www.w3.org/1998/Math/MathML\"&gt;&lt;d:mi&gt;d&lt;/d:mi&gt;&lt;/d:math&gt;. The exchange forces, &lt;e:math xmlns:e=\"http://www.w3.org/1998/Math/MathML\"&gt;&lt;e:mrow&gt;&lt;e:msub&gt;&lt;e:mi&gt;F&lt;/e:mi&gt;&lt;e:mi&gt;ex&lt;/e:mi&gt;&lt;/e:msub&gt;&lt;e:mrow&gt;&lt;e:mo&gt;(&lt;/e:mo&gt;&lt;e:mi&gt;d&lt;/e:mi&gt;&lt;e:mo&gt;)&lt;/e:mo&gt;&lt;/e:mrow&gt;&lt;/e:mrow&gt;&lt;/e:math&gt;, are calculated based on the Hellmann-Feynman theorem. We show that structural relaxations of tip and sample due to their interaction need to be taken into account. Due to the exchange interaction the relaxations depend on the alignment between tip and adatom magnetization—an effect which will affect the tunneling magnetoresistance that can be measured by a spin-polarized scanning tunneling microscope. A maximum in the exchange energy and force curves is obtained for magnetic adatoms at tip-adatom separations of about 3 to 4 Å. The exchange forces with an Fe terminated tip reach a maximum value of up to 0.2 and 0.6 nN for Co and Mn adatoms, respectively, and prefer an antiferromagnetic coupling. Surprisingly, we also find an exchange force of up to 0.2 nN for Ir adatoms. We analyze the exchange interaction between tip and adatom based on the spin-polarized electronic structure of the coupled system. A competition occurs between long-range Zener-type indirect double exchange favoring ferromagnetic coupling and short-range direct &lt;f:math xmlns:f=\"http://www.w3.org/1998/Math/MathML\"&gt;&lt;f:mrow&gt;&lt;f:mi&gt;d&lt;/f:mi&gt;&lt;f:mtext&gt;−&lt;/f:mtext&gt;&lt;f:mi&gt;d&lt;/f:mi&gt;&lt;/f:mrow&gt;&lt;/f:math&gt; antiferromagnetic exchange. For the Ir adatom the interaction can be explained from the spin-dependent hybridization with the tip apex atom. Our results show that magnetic adatoms on Mn/W(110) are a promising system to study exchange forces at the single-atom level via magnetic exchange force microscopy. &lt;jats:supplementary-material&gt; &lt;jats:copyright-statement&gt;Published ","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":"99 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143897838","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dynamical electronic correlations and chiral magnetism in the van der Waals magnet Fe4GeTe2","authors":"Md. Nur Hasan, Nastaran Salehi, Felix Sorgenfrei, Anna Delin, Igor Di Marco, Anders Bergman, Manuel Pereiro, Patrik Thunström, Olle Eriksson, Debjani Karmakar","doi":"10.1103/physrevb.111.134449","DOIUrl":"https://doi.org/10.1103/physrevb.111.134449","url":null,"abstract":"Among the quasi-two-dimensional van der Waals magnetic systems, Fe</a:mi>4</a:mn></a:msub>Ge</a:mi>Te</a:mi>2</a:mn></a:msub></a:mrow></a:math> makes a profound impact due to its near-room-temperature ferromagnetic behavior and the complex magnetothermal phase diagram exhibiting multiple phase transformations, as observed from magnetization and magnetotransport measurements. A complete analysis of these phase transformations in light of electronic correlation and its impact on the underlying magnetic interactions remain unexplored in the existing literature. Using first-principles methodologies, incorporating the dynamical nature of electron correlation, we have analyzed the interplay of the direction of magnetization in an easy-plane and easy-axis manner with the underlying crystal symmetry, which reveals the opening of a pseudogap feature beyond the spin-reorientation transition temperature. The impact of dynamical correlation on the calculated magnetic circular dichroism and x-ray absorption spectrum of the <d:math xmlns:d=\"http://www.w3.org/1998/Math/MathML\"><d:mrow><d:mi>L</d:mi></d:mrow></d:math>-edge of Fe atoms compare well with existing experimental observations. The calculated intersite Heisenberg exchange interactions display a complicated nature, depending upon the pairwise interactions among the two inequivalent Fe sites, indicating a Ruderman-Kittel-Kasuya-Yosida-like behavior of the magnetic interactions. We note the existence of significant anisotropic and antisymmetric exchange interactions, resulting in a chirality in the magnetic behavior of the system. Subsequent investigation of the dynamical aspects of magnetism in <e:math xmlns:e=\"http://www.w3.org/1998/Math/MathML\"><e:mrow><e:msub><e:mi mathvariant=\"normal\">Fe</e:mi><e:mn>4</e:mn></e:msub><e:mi>Ge</e:mi><e:msub><e:mi mathvariant=\"normal\">Te</e:mi><e:mn>2</e:mn></e:msub></e:mrow></e:math> and the respective magnetothermal phase diagram reveals that the dynamical nature of spins and the decoupling of the magnetic properties for both sites of Fe is crucial to explain all the experimentally observed phase transformations. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20082,"journal":{"name":"Physical Review B","volume":"38 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143897840","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}