Pub Date : 2024-08-19DOI: 10.1103/physrevmaterials.8.086001
L. Pizzagalli, S. Brochard, J. Godet, J. Durinck
Motivated by contradicting reports in the literature, we have investigated the structural stability of tungsten nanoparticles using density functional theory calculations. The comparison of BCC, FCC, A15, disordered, and icosahedral configurations unequivocally shows that BCC is, energetically, the most stable structure when the number of atoms is greater than 40. A disordered structure is more stable for smaller sizes. This result conflicts with an earlier theoretical study on transition metal nanoparticles, based on a semi-empirical modeling of nanoparticles energetics [D. Tománek et al., Phys. Rev. B28, 665 (1983)]. Examining this latter work in the light of our results suggests that an inappropriate description of cluster geometry is the source of the discrepancy. Finally, we improve the accuracy of the semi-empirical model proposed in this work, which will be useful to calculate nanoparticle energies for larger sizes.
{"title":"Structural stability of tungsten nanoparticles","authors":"L. Pizzagalli, S. Brochard, J. Godet, J. Durinck","doi":"10.1103/physrevmaterials.8.086001","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.086001","url":null,"abstract":"Motivated by contradicting reports in the literature, we have investigated the structural stability of tungsten nanoparticles using density functional theory calculations. The comparison of BCC, FCC, A15, disordered, and icosahedral configurations unequivocally shows that BCC is, energetically, the most stable structure when the number of atoms is greater than 40. A disordered structure is more stable for smaller sizes. This result conflicts with an earlier theoretical study on transition metal nanoparticles, based on a semi-empirical modeling of nanoparticles energetics [D. Tománek <i>et al.</i>, <span>Phys. Rev. B</span> <b>28</b>, 665 (1983)]. Examining this latter work in the light of our results suggests that an inappropriate description of cluster geometry is the source of the discrepancy. Finally, we improve the accuracy of the semi-empirical model proposed in this work, which will be useful to calculate nanoparticle energies for larger sizes.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"45 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206147","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-19DOI: 10.1103/physrevmaterials.8.084005
M. Amirabbasi, P. Kratzer
The two-dimensional van der Waals (vdW) materials display antiferromagnetic ordering of the magnetic moments at the transition metal ions. The possibility to exfoliate thin layers that preserve the magnetic order makes these materials interesting for numerous applications in devices that require integration of flexible patches of magnetic materials, e.g., in antiferromagnetic spintronics. Hence, an improved understanding of their magnetic properties is desirable. Here, we parametrize spin Hamiltonians for a monolayer of all four materials of this class using density functional theory plus Hubbard calculations. We provide a step-by-step guide for calculating the magnetic exchange interactions and magnetic anisotropy energy using the (non)collinear approach with a suitably chosen for each material. It is found that the biquadratic interactions gain in importance while moving through the series. Retaining the leading terms of a Holstein-Primakoff-transformed spin Hamiltonian, the magnon spectra are calculated. While is found to be an almost isotropic antiferromagnet with a tiny gap, the biquadratic interaction opens an increasingly wider gap for , and . In line with this observation, Monte Carlo simulations demonstrate that the biquadratic interactions contribute to a systematic rise in the Néel temperature from to .
二维范德华（vdW）材料 MPS3（M=Mn,Fe,Co,Ni）显示了过渡金属离子磁矩的反铁磁有序性。由于可以剥离出保持磁序的薄层，这些材料在需要集成灵活的磁性材料贴片的设备（如反铁磁性自旋电子学）中有着广泛的应用前景。因此，我们需要更好地了解它们的磁性能。在这里，我们利用密度泛函理论和哈伯德 U 计算，对该类所有四种材料的单层自旋哈密顿进行了参数化。我们提供了使用（非）对偶 DFT+U(+SOC)方法计算磁交换相互作用和磁各向异性能的分步指南，并为每种材料适当选择了 U。研究发现，在 3d 系列中，双四次方相互作用的重要性不断增加。保留 Holstein-Primakoff 变换自旋哈密顿的前导项，计算了磁子谱。结果发现，MnPS3 几乎是各向同性的反铁磁体，具有微小的间隙，而对于 FePS3、CoPS3 和 NiPS3 来说，双四次方相互作用打开了越来越大的间隙。根据这一观察结果，蒙特卡洛模拟证明，从 FePS3 到 NiPS3，双四次方相互作用导致了内耳温度的系统性上升。
{"title":"Effect of biquadratic magnetic exchange interaction in the 2D antiferromagnets MPS3 (M=Mn,Fe,Co,Ni)","authors":"M. Amirabbasi, P. Kratzer","doi":"10.1103/physrevmaterials.8.084005","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.084005","url":null,"abstract":"The two-dimensional van der Waals (vdW) materials <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>M</mi><msub><mi>PS</mi><mn>3</mn></msub><mspace width=\"0.16em\"></mspace><mrow><mo>(</mo><mi>M</mi><mo>=</mo><mi>Mn</mi><mo>,</mo><mi>Fe</mi><mo>,</mo><mi>Co</mi><mo>,</mo><mi>Ni</mi><mo>)</mo></mrow></mrow></math> display antiferromagnetic ordering of the magnetic moments at the transition metal ions. The possibility to exfoliate thin layers that preserve the magnetic order makes these materials interesting for numerous applications in devices that require integration of flexible patches of magnetic materials, e.g., in antiferromagnetic spintronics. Hence, an improved understanding of their magnetic properties is desirable. Here, we parametrize spin Hamiltonians for a monolayer of all four materials of this class using density functional theory plus Hubbard <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>U</mi></math> calculations. We provide a step-by-step guide for calculating the magnetic exchange interactions and magnetic anisotropy energy using the (non)collinear <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>DFT</mi><mo>+</mo><mi>U</mi><mo>(</mo><mo>+</mo><mi>SOC</mi><mo>)</mo></mrow></math> approach with a suitably chosen <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>U</mi></math> for each material. It is found that the biquadratic interactions gain in importance while moving through the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>3</mn><mi>d</mi></mrow></math> series. Retaining the leading terms of a Holstein-Primakoff-transformed spin Hamiltonian, the magnon spectra are calculated. While <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>MnPS</mi><mn>3</mn></msub></math> is found to be an almost isotropic antiferromagnet with a tiny gap, the biquadratic interaction opens an increasingly wider gap for <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>FePS</mi><mn>3</mn></msub><mo>,</mo><mo> </mo><msub><mi>CoPS</mi><mn>3</mn></msub></math>, and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>NiPS</mi><mn>3</mn></msub></math>. In line with this observation, Monte Carlo simulations demonstrate that the biquadratic interactions contribute to a systematic rise in the Néel temperature from <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>FePS</mi><mn>3</mn></msub></math> to <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>NiPS</mi><mn>3</mn></msub></math>.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"57 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206151","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-19DOI: 10.1103/physrevmaterials.8.l080601
Andrzej Ptok, Surajit Basak, Aksel Kobiałka, Małgorzata Sternik, Jan Łażewski, Paweł T. Jochym, Andrzej M. Oleś, Przemysław Piekarz
Electron-correlation-driven phonon soft modes have been recently reported in the antiferromagnetic kagome FeGe compound and associated with the observed charge density wave (CDW). In this paper, we present a systematic investigation of the CDW origin in the context of the ab initio lattice dynamics study. Performing the group theory analysis of the aforementioned soft modes, we found that the stable structure has the Immm symmetry and can be achieved by shifts of Ge atoms. The occurrence of two soft modes induces the first-order phase transition, which leads to the CDW order. Additionally, we show that the final structure realizes a distorted honeycomb Ge lattice, as well as a nonflat kagome-like Fe net. For completeness, we present the electronic properties calculations. From the theoretical STM topography simulation, we indicate that the observed CDW occurs in the deformed honeycomb Ge sublattice.
最近有报道称，反铁磁性卡戈梅铁锗化合物中存在电子相关驱动的声子软模式，并与观测到的电荷密度波（CDW）有关。在本文中，我们结合 ab initio 晶格动力学研究，对 CDW 的起源进行了系统研究。通过对上述软模式进行群论分析，我们发现稳定结构具有 Immm 对称性，可以通过 Ge 原子的移动来实现。两个软模式的出现引起了一阶相变，从而导致了 CDW 阶。此外，我们还展示了最终结构实现了扭曲的蜂窝状 Ge 晶格，以及非扁平的卡戈米状 Fe 网。为了完整起见，我们还介绍了电子特性计算。通过 STM 拓扑理论模拟，我们发现观察到的 CDW 发生在变形的蜂窝状 Ge 子晶格中。
{"title":"Lattice dynamics study of electron-correlation-induced charge density wave in antiferromagnetic kagome metal FeGe","authors":"Andrzej Ptok, Surajit Basak, Aksel Kobiałka, Małgorzata Sternik, Jan Łażewski, Paweł T. Jochym, Andrzej M. Oleś, Przemysław Piekarz","doi":"10.1103/physrevmaterials.8.l080601","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.l080601","url":null,"abstract":"Electron-correlation-driven phonon soft modes have been recently reported in the antiferromagnetic kagome FeGe compound and associated with the observed charge density wave (CDW). In this paper, we present a systematic investigation of the CDW origin in the context of the <i>ab initio</i> lattice dynamics study. Performing the group theory analysis of the aforementioned soft modes, we found that the stable structure has the Immm symmetry and can be achieved by shifts of Ge atoms. The occurrence of two soft modes induces the first-order phase transition, which leads to the CDW order. Additionally, we show that the final structure realizes a distorted honeycomb Ge lattice, as well as a nonflat kagome-like Fe net. For completeness, we present the electronic properties calculations. From the theoretical STM topography simulation, we indicate that the observed CDW occurs in the deformed honeycomb Ge sublattice.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"10 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206144","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-19DOI: 10.1103/physrevmaterials.8.084004
Efstratios Manousakis
There are many reports of a surprisingly high charge-carrier density with sizable mobility in photoexcited two-dimensional (2D) halide perovskites despite their unusually high exciton binding energy. In this work we study the thermodynamic quasiequilibrium of the relative population of photoexcited free quasielectron/quasihole pairs, neutral excitons, and excitonic trions, in 2D materials that support such excitonic complexes with large binding energy. We derive and solve the general Saha equations which describe the detailed balance of such a system of photoexcited electronic degrees of freedom forming a multicomponent fluid of excitations in thermodynamic quasiequilibrium. The solution to these equations, for the special case of 2D perovskites where the reported exciton and excitonic trion binding energies are of the order of 0.3–0.4 eV for the former and 30–40 meV for the latter, reveals that while the charge-neutral excitonic population dominates all other excitations, at room temperature and below, the excitonic trion component can be the dominant population among charge carriers. We also argue that trionic hopping can take place via a tunneling mechanism which is speculated to play a role in a novel charge-transport mechanism.
尽管二维卤化物包晶石的激子结合能异常高，但有许多报告指出，在光激发二维卤化物包晶石中，电荷载流子密度出奇地高，并具有相当大的迁移率。在这项工作中，我们研究了支持这种具有高结合能的激子复合物的二维材料中，光激发自由准电子/准空穴对、中性激子和激子三离子的相对数量的热力学准平衡。我们推导并求解了一般萨哈方程，该方程描述了这种光激发电子自由度系统在热力学准平衡状态下形成多组分激发流体的详细平衡情况。在二维包晶的特殊情况下，前者的激子和激子三离子结合能分别为 0.3-0.4 eV 和 30-40 meV，这些方程的求解结果表明，虽然电荷中性的激子群在所有其他激子中占主导地位，但在室温及室温以下，激子三离子成分可以成为电荷载流子中的主导群。我们还认为，三离子跳变可以通过隧道机制发生，据推测，隧道机制在新型电荷传输机制中发挥了作用。
{"title":"Excitonic trion population in two-dimensional halide perovskites","authors":"Efstratios Manousakis","doi":"10.1103/physrevmaterials.8.084004","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.084004","url":null,"abstract":"There are many reports of a surprisingly high charge-carrier density with sizable mobility in photoexcited two-dimensional (2D) halide perovskites despite their unusually high exciton binding energy. In this work we study the thermodynamic quasiequilibrium of the relative population of photoexcited free quasielectron/quasihole pairs, neutral excitons, and excitonic trions, in 2D materials that support such excitonic complexes with large binding energy. We derive and solve the general Saha equations which describe the detailed balance of such a system of photoexcited electronic degrees of freedom forming a multicomponent fluid of excitations in thermodynamic quasiequilibrium. The solution to these equations, for the special case of 2D perovskites where the reported exciton and excitonic trion binding energies are of the order of 0.3–0.4 eV for the former and 30–40 meV for the latter, reveals that while the charge-neutral excitonic population dominates all other excitations, at room temperature and below, the excitonic trion component can be the dominant population among charge carriers. We also argue that trionic hopping can take place via a tunneling mechanism which is speculated to play a role in a novel charge-transport mechanism.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"13 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206137","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-19DOI: 10.1103/physrevmaterials.8.085202
Jizhang Wang, Meng Ye, Xiaomi Guo, Yang Li, Nianlong Zou, He Li, Zetao Zhang, Sibo Zhao, Zhiming Xu, Haowei Chen, Dezhao Wu, Ting Bao, Yong Xu, Wenhui Duan
One of the most important nonlinear optical (NLO) effects is the second-harmonic generation (SHG), and crystals with strong SHG effects are called NLO crystals. The traditional anion group theory has guided the early discovery of NLO crystals, but the variety of NLO-active motifs discovered so far is limited. In this study, material-type unbiased high-throughput first-principles calculations are performed to screen thousands of materials in a materials database for NLO crystals at target frequencies. The electronic, linear, and nonlinear optical properties of these materials are calculated. Among them, 40 NLO crystals suitable for mid-infrared (MIR) frequencies and 5 for deep-ultraviolet (DUV) frequencies are identified, from 229 materials to which scissors correction is applied. As an extension, several NLO-active motifs that dominate the SHG response are identified, and they all show good transferability among similar materials. Furthermore, for materials where scissors correction cannot be applied due to the lack of accurate bandgap value in the database, a recommendation list of NLO crystals based on the scaling law of bandgap and SHG susceptibility is presented. The discovery of new NLO crystals and NLO-active motifs beyond traditional methods will greatly accelerate the applications of NLO crystals at DUV and MIR frequencies and enrich our understanding in the search and design of new NLO crystals.
{"title":"Unbiased screening of deep-ultraviolet and mid-infrared nonlinear optical crystals: Long-neglected covalent and mixed-cation motifs","authors":"Jizhang Wang, Meng Ye, Xiaomi Guo, Yang Li, Nianlong Zou, He Li, Zetao Zhang, Sibo Zhao, Zhiming Xu, Haowei Chen, Dezhao Wu, Ting Bao, Yong Xu, Wenhui Duan","doi":"10.1103/physrevmaterials.8.085202","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.085202","url":null,"abstract":"One of the most important nonlinear optical (NLO) effects is the second-harmonic generation (SHG), and crystals with strong SHG effects are called NLO crystals. The traditional anion group theory has guided the early discovery of NLO crystals, but the variety of NLO-active motifs discovered so far is limited. In this study, material-type unbiased high-throughput first-principles calculations are performed to screen thousands of materials in a materials database for NLO crystals at target frequencies. The electronic, linear, and nonlinear optical properties of these materials are calculated. Among them, 40 NLO crystals suitable for mid-infrared (MIR) frequencies and 5 for deep-ultraviolet (DUV) frequencies are identified, from 229 materials to which scissors correction is applied. As an extension, several NLO-active motifs that dominate the SHG response are identified, and they all show good transferability among similar materials. Furthermore, for materials where scissors correction cannot be applied due to the lack of accurate bandgap value in the database, a recommendation list of NLO crystals based on the scaling law of bandgap and SHG susceptibility is presented. The discovery of new NLO crystals and NLO-active motifs beyond traditional methods will greatly accelerate the applications of NLO crystals at DUV and MIR frequencies and enrich our understanding in the search and design of new NLO crystals.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"16 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206166","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-16DOI: 10.1103/physrevmaterials.8.085001
Arushi, Raul Cardoso-Gil, Christoph Geibel
Recently, a new type of unconventional superconductivity with a field-induced transition between two different superconducting (SC) states was discovered in the heavy fermion system . This unusual SC state was proposed to be based on specific symmetries of the underlying structure, i.e., a globally centrosymmetric layered structure, but where the Ce layers themselves lack inversion symmetry. This new type of SC state has attracted strong interest, prompting the search for further heavy fermion systems crystallizing in structures with appropriate symmetries. We report the discovery and the study of a new Ce-based heavy fermion system with a globally centrosymmetric structure but without inversion symmetry on the Ce-site, . A single crystal x-ray diffraction study revealed an orthorhombic type structure. Resistivity, specific heat, and magnetization measurements indicate a moderate-heavy fermion behavior with a Kondo energy scale of the order of 40 K. Most experimental results suggest the absence of magnetic order, but a tiny anomaly in the specific heat opens the possibility for a very weak, itinerant type of ordering.
{"title":"Ce2Ir3Ga5 : A new locally noncentrosymmetric heavy fermion system","authors":"Arushi, Raul Cardoso-Gil, Christoph Geibel","doi":"10.1103/physrevmaterials.8.085001","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.085001","url":null,"abstract":"Recently, a new type of unconventional superconductivity with a field-induced transition between two different superconducting (SC) states was discovered in the heavy fermion system <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>CeRh</mi><mn>2</mn></msub><msub><mi>As</mi><mn>2</mn></msub></mrow></math>. This unusual SC state was proposed to be based on specific symmetries of the underlying structure, i.e., a globally centrosymmetric layered structure, but where the Ce layers themselves lack inversion symmetry. This new type of SC state has attracted strong interest, prompting the search for further heavy fermion systems crystallizing in structures with appropriate symmetries. We report the discovery and the study of a new Ce-based heavy fermion system with a globally centrosymmetric structure but without inversion symmetry on the Ce-site, <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Ce</mi><mn>2</mn></msub><msub><mi>Ir</mi><mn>3</mn></msub><msub><mi>Ga</mi><mn>5</mn></msub></mrow></math>. A single crystal x-ray diffraction study revealed an orthorhombic <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi mathvariant=\"normal\">U</mi><mn>2</mn></msub><msub><mi>Co</mi><mn>3</mn></msub><msub><mi>Si</mi><mn>5</mn></msub></mrow></math> type structure. Resistivity, specific heat, and magnetization measurements indicate a moderate-heavy fermion behavior with a Kondo energy scale of the order of 40 K. Most experimental results suggest the absence of magnetic order, but a tiny anomaly in the specific heat opens the possibility for a very weak, itinerant type of ordering.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"8 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206146","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-15DOI: 10.1103/physrevmaterials.8.084408
Banasree S. Mou, Xinshu Zhang, Li Xiang, Yuanyuan Xu, Ruidan Zhong, Robert J. Cava, Haidong Zhou, Zhigang Jiang, Dmitry Smirnov, Natalia Drichko, Stephen M. Winter
Co-based materials have recently been explored because of their potential to realize complex bond-dependent anisotropic magnetism. Prominent examples include , and . In order to provide insight into the magnetic interactions in these compounds, we make a comparative analysis of their local crystal electric field excitations spectra via Raman scattering measurements. Combining these measurements with theoretical analysis confirms the validity of single-ion ground states for all compounds, and provides accurate experimental estimates of the local crystal distortions, which play a prominent role in the magnetic couplings between spin-orbital coupled Co moments.
由于 Co 基材料具有实现复杂的各向异性磁性键的潜力，最近人们对它们进行了探索。突出的例子包括 Na2Co2TeO6、BaCo2(AsO4)2、Na2BaCo(PO4)2 和 CoX2（X=Cl、Br、I）。为了深入了解这些化合物中的磁相互作用，我们通过拉曼散射测量对它们的局部晶体电场激发光谱进行了比较分析。将这些测量结果与理论分析相结合，证实了所有化合物的 jeff=1/2 单离子基态的有效性，并提供了对局部晶体畸变的精确实验估计，而晶体畸变在自旋轨道耦合 Co 矩之间的磁耦合中起着重要作用。
{"title":"Comparative Raman scattering study of crystal field excitations in Co-based quantum magnets","authors":"Banasree S. Mou, Xinshu Zhang, Li Xiang, Yuanyuan Xu, Ruidan Zhong, Robert J. Cava, Haidong Zhou, Zhigang Jiang, Dmitry Smirnov, Natalia Drichko, Stephen M. Winter","doi":"10.1103/physrevmaterials.8.084408","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.084408","url":null,"abstract":"Co-based materials have recently been explored because of their potential to realize complex bond-dependent anisotropic magnetism. Prominent examples include <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Na</mi><mn>2</mn></msub><msub><mi>Co</mi><mn>2</mn></msub><msub><mi>TeO</mi><mn>6</mn></msub></mrow><mo>,</mo><mo> </mo><mrow><msub><mi>BaCo</mi><mn>2</mn></msub><msub><mrow><mo>(</mo><msub><mi>AsO</mi><mn>4</mn></msub><mo>)</mo></mrow><mn>2</mn></msub></mrow><mo>,</mo><mo> </mo><mrow><msub><mi>Na</mi><mn>2</mn></msub><mi>BaCo</mi><msub><mrow><mo>(</mo><msub><mi>PO</mi><mn>4</mn></msub><mo>)</mo></mrow><mn>2</mn></msub></mrow></math>, and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mrow><mi>Co</mi><mi mathvariant=\"italic\">X</mi></mrow><mn>2</mn></msub></math> <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo>(</mo><mi>X</mi><mo>=</mo><mi>Cl</mi><mo>,</mo><mi>Br</mi><mo>,</mo><mi mathvariant=\"normal\">I</mi><mo>)</mo></mrow></math>. In order to provide insight into the magnetic interactions in these compounds, we make a comparative analysis of their local crystal electric field excitations spectra via Raman scattering measurements. Combining these measurements with theoretical analysis confirms the validity of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>j</mi><mi>eff</mi></msub><mo>=</mo><mn>1</mn><mo>/</mo><mn>2</mn></mrow></math> single-ion ground states for all compounds, and provides accurate experimental estimates of the local crystal distortions, which play a prominent role in the magnetic couplings between spin-orbital coupled Co moments.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"2 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206148","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We detail the optimized synthesis of the <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi>Mo</mi><mn>3</mn></msub><msub><mi mathvariant="normal">O</mi><mn>8</mn></msub></mrow></math>-type cluster Mott insulator (CMI) <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi mathvariant="normal">Na</mi><mn>3</mn></msub><msub><mi mathvariant="normal">Sc</mi><mn>2</mn></msub><msub><mrow><mo>(</mo><msub><mi>MoO</mi><mn>4</mn></msub><mo>)</mo></mrow><mn>2</mn></msub><msub><mi mathvariant="normal">Mo</mi><mn>3</mn></msub><msub><mi mathvariant="normal">O</mi><mn>8</mn></msub></mrow></math>, which has been considered a candidate for realizing the spin liquid ground state. The optimized <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi mathvariant="normal">Na</mi><mn>3</mn></msub><msub><mi mathvariant="normal">Sc</mi><mn>2</mn></msub><msub><mrow><mo>(</mo><msub><mi>MoO</mi><mn>4</mn></msub><mo>)</mo></mrow><mn>2</mn></msub><msub><mi mathvariant="normal">Mo</mi><mn>3</mn></msub><msub><mi mathvariant="normal">O</mi><mn>8</mn></msub></mrow></math>, characterized by x-ray diffraction, energy-dispersive x-ray spectroscopy, and magnetic and heat capacity measurements exhibited an effective magnetic moment close to the ideal 1.73 <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>μ</mi><mi mathvariant="normal">B</mi></msub></math> for S = 1/2 spin and magnetic ordering at ∼5 K. These observations categorize <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi mathvariant="normal">Na</mi><mn>3</mn></msub><msub><mi mathvariant="normal">Sc</mi><mn>2</mn></msub><msub><mrow><mo>(</mo><msub><mi>MoO</mi><mn>4</mn></msub><mo>)</mo></mrow><mn>2</mn></msub><msub><mi mathvariant="normal">Mo</mi><mn>3</mn></msub><msub><mi mathvariant="normal">O</mi><mn>8</mn></msub></mrow></math> as the second <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi>Mo</mi><mn>3</mn></msub><msub><mi mathvariant="normal">O</mi><mn>8</mn></msub></mrow></math>-type CMI to achieve a magnetic ground state, following <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi mathvariant="normal">Li</mi><mn>2</mn></msub><msub><mi>InMo</mi><mn>3</mn></msub><msub><mi mathvariant="normal">O</mi><mn>8</mn></msub></mrow></math>. They highlight the stabilization of the magnetic ground state over the theoretically anticipated quantum spin liquid state through precise valence and chemical disorder tuning. Our findings challenge the existing theory that the magnetic ground state of <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi>Mo</mi><mn>3</mn></msub><msub><mi mathvariant="normal">O</mi><mn>8</mn></msub></mrow></math>-type CMIs is determined by the breathing parameter, instead showing that magnetic order is suppressed by spin defects. This study underscores the crucial role of chemical precision in investigating quantum magnetism. It suggests that precise tuning of valence states could induce magnetic ordering in pre
我们详细介绍了 Mo3O8 型簇状莫特绝缘体（CMI）Na3Sc2(MoO4)2Mo3O8 的优化合成，它一直被认为是实现自旋液体基态的候选材料。经过优化的 Na3Sc2(MoO4)2Mo3O8 通过 X 射线衍射、能量色散 X 射线光谱以及磁性和热容量测量，在 S = 1/2 自旋和 5 K 磁有序的条件下，有效磁矩接近理想的 1.73 μB。他们强调了通过精确的价态和化学无序调整，磁基态比理论上预期的量子自旋液态更加稳定。我们的研究结果挑战了现有的理论，即 Mo3O8 型 CMI 的磁基态由呼吸参数决定，相反，研究结果表明磁有序受到自旋缺陷的抑制。这项研究强调了化学精确性在研究量子磁性中的关键作用。它表明，对价态的精确调谐可以诱导以前无磁性的 Mo3O8 型 CMIs 产生磁有序。此外，有关量子自旋液体存在的负面发现突出了应用研究以及从理论和实验两方面重新评估我们对电子态的基本认识的必要性。
{"title":"Magnetic ordering of the Mo3O8-type cluster Mott insulator Na3Sc2(MoO4)2Mo3O8 with spin-1/2 triangular lattice prepared via optimal synthesis","authors":"Yuya Haraguchi, Daigo Ishikita, Hiroko Aruga Katori","doi":"10.1103/physrevmaterials.8.084409","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.084409","url":null,"abstract":"We detail the optimized synthesis of the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Mo</mi><mn>3</mn></msub><msub><mi mathvariant=\"normal\">O</mi><mn>8</mn></msub></mrow></math>-type cluster Mott insulator (CMI) <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi mathvariant=\"normal\">Na</mi><mn>3</mn></msub><msub><mi mathvariant=\"normal\">Sc</mi><mn>2</mn></msub><msub><mrow><mo>(</mo><msub><mi>MoO</mi><mn>4</mn></msub><mo>)</mo></mrow><mn>2</mn></msub><msub><mi mathvariant=\"normal\">Mo</mi><mn>3</mn></msub><msub><mi mathvariant=\"normal\">O</mi><mn>8</mn></msub></mrow></math>, which has been considered a candidate for realizing the spin liquid ground state. The optimized <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi mathvariant=\"normal\">Na</mi><mn>3</mn></msub><msub><mi mathvariant=\"normal\">Sc</mi><mn>2</mn></msub><msub><mrow><mo>(</mo><msub><mi>MoO</mi><mn>4</mn></msub><mo>)</mo></mrow><mn>2</mn></msub><msub><mi mathvariant=\"normal\">Mo</mi><mn>3</mn></msub><msub><mi mathvariant=\"normal\">O</mi><mn>8</mn></msub></mrow></math>, characterized by x-ray diffraction, energy-dispersive x-ray spectroscopy, and magnetic and heat capacity measurements exhibited an effective magnetic moment close to the ideal 1.73 <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>μ</mi><mi mathvariant=\"normal\">B</mi></msub></math> for S = 1/2 spin and magnetic ordering at ∼5 K. These observations categorize <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi mathvariant=\"normal\">Na</mi><mn>3</mn></msub><msub><mi mathvariant=\"normal\">Sc</mi><mn>2</mn></msub><msub><mrow><mo>(</mo><msub><mi>MoO</mi><mn>4</mn></msub><mo>)</mo></mrow><mn>2</mn></msub><msub><mi mathvariant=\"normal\">Mo</mi><mn>3</mn></msub><msub><mi mathvariant=\"normal\">O</mi><mn>8</mn></msub></mrow></math> as the second <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Mo</mi><mn>3</mn></msub><msub><mi mathvariant=\"normal\">O</mi><mn>8</mn></msub></mrow></math>-type CMI to achieve a magnetic ground state, following <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi mathvariant=\"normal\">Li</mi><mn>2</mn></msub><msub><mi>InMo</mi><mn>3</mn></msub><msub><mi mathvariant=\"normal\">O</mi><mn>8</mn></msub></mrow></math>. They highlight the stabilization of the magnetic ground state over the theoretically anticipated quantum spin liquid state through precise valence and chemical disorder tuning. Our findings challenge the existing theory that the magnetic ground state of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Mo</mi><mn>3</mn></msub><msub><mi mathvariant=\"normal\">O</mi><mn>8</mn></msub></mrow></math>-type CMIs is determined by the breathing parameter, instead showing that magnetic order is suppressed by spin defects. This study underscores the crucial role of chemical precision in investigating quantum magnetism. It suggests that precise tuning of valence states could induce magnetic ordering in pre","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"18 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206153","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-15DOI: 10.1103/physrevmaterials.8.084202
R. Fukushima, V. N. Antonov, M. M. Otrokov, T. T. Sasaki, R. Akiyama, K. Sumida, K. Ishihara, S. Ichinokura, K. Tanaka, Y. Takeda, D. P. Salinas, S. V. Eremeev, E. V. Chulkov, A. Ernst, T. Hirahara
Intrinsic magnetic topological insulators, in which magnetism and topology are inherently combined, are excellent systems to realize exotic phenomena such as the quantum anomalous Hall effect. However, there are many reports that show that the experimental samples are not so ideal and the effect of the unintentional disorder in these systems needs to be considered carefully. In this study, we investigate the role of misplaced magnetic atoms as well as nonmagnetic elements in the intrinsic magnetic topological insulator heterostructures based on and . We find that Mn atoms are not only placed at the central layer of the septuple layer (SL) but also intermix with Bi (antisite Mn) as well as reside in the van der Waals (vdW) gap. Through a detailed comparison between the experimental and theoretical x-ray magnetic circular dichroism (XMCD) spectra, we find that the antisite Mn is coupled ferromagnetically, whereas the vdW Mn couple antiferromagnetically to the Mn in the central atomic plane of the SL. Furthermore, we detect a clear XMCD signal in nonmagnetic Se, providing unambiguous evidence of its magnetic interaction with Mn.
{"title":"Direct evidence of induced magnetic moment in Se and the role of misplaced Mn in MnBi2Se4-based intrinsic magnetic topological insulator heterostructures","authors":"R. Fukushima, V. N. Antonov, M. M. Otrokov, T. T. Sasaki, R. Akiyama, K. Sumida, K. Ishihara, S. Ichinokura, K. Tanaka, Y. Takeda, D. P. Salinas, S. V. Eremeev, E. V. Chulkov, A. Ernst, T. Hirahara","doi":"10.1103/physrevmaterials.8.084202","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.084202","url":null,"abstract":"Intrinsic magnetic topological insulators, in which magnetism and topology are inherently combined, are excellent systems to realize exotic phenomena such as the quantum anomalous Hall effect. However, there are many reports that show that the experimental samples are not so ideal and the effect of the unintentional disorder in these systems needs to be considered carefully. In this study, we investigate the role of misplaced magnetic atoms as well as nonmagnetic elements in the intrinsic magnetic topological insulator heterostructures based on <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>MnBi</mi><mn>2</mn></msub><msub><mi>Se</mi><mn>4</mn></msub></mrow></math> and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Bi</mi><mn>2</mn></msub><msub><mi>Se</mi><mn>3</mn></msub></mrow></math>. We find that Mn atoms are not only placed at the central layer of the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>MnBi</mi><mn>2</mn></msub><msub><mi>Se</mi><mn>4</mn></msub></mrow></math> septuple layer (SL) but also intermix with Bi (antisite Mn) as well as reside in the van der Waals (vdW) gap. Through a detailed comparison between the experimental and theoretical x-ray magnetic circular dichroism (XMCD) spectra, we find that the antisite Mn is coupled ferromagnetically, whereas the vdW Mn couple antiferromagnetically to the Mn in the central atomic plane of the SL. Furthermore, we detect a clear XMCD signal in nonmagnetic Se, providing unambiguous evidence of its magnetic interaction with Mn.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"22 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206149","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-15DOI: 10.1103/physrevmaterials.8.085401
Yubi Chen, Rongying Jin, Bolin Liao, Sai Mu
Topological materials are often associated with exceptional thermoelectric properties. Orthorhombic is a topological semimetal consisting of alternating layers of Ba, Sb, and MnSb. A recent experiment demonstrates that has a low thermal conductivity and modest thermopower, promising as a thermoelectric material. Through first-principles calculations with Coulomb repulsion and spin-orbit coupling included, we studied the electronic structure, phononic structure, and thermoelectric transport properties of in depth. We find that exhibits a low lattice thermal conductivity, owing to the scattering of the acoustic phonons with low-frequency optical modes. Using the linearized Boltzmann transport theory with a constant relaxation time approximation, the thermopower is further calculated and an intriguing goniopolar transport behavior, which is associated with both -type and -type conduction along separate transport directions simultaneously, is observed. We propose that the figure of merit can be enhanced via doping in which electrical conductivity is increased while the thermopower remains undiminished. is a potential platform for elucidating complex band structure effects and topological phenomena, paving the way to explore rich physics in low-dimensional systems.
拓扑材料通常具有特殊的热电特性。正交态 BaMnSb2 是一种拓扑半金属，由 Ba、Sb 和 MnSb 层交替组成。最近的一项实验表明，BaMnSb2 具有较低的热导率和适度的热功率，有望成为一种热电材料。通过包含库仑斥力和自旋轨道耦合的第一性原理计算，我们深入研究了 BaMnSb2 的电子结构、声波结构和热电传输特性。我们发现，由于声子与低频光学模式的散射，BaMnSb2 表现出较低的晶格热导率。利用线性化玻尔兹曼输运理论和恒定弛豫时间近似，我们进一步计算了热功率，并观察到一种有趣的双极性输运行为，它同时与沿不同输运方向的 n 型和 p 型传导有关。我们提出，可以通过掺杂来提高优点系数，从而在提高导电性的同时保持热功率不变。BaMnSb2 是阐明复杂带状结构效应和拓扑现象的潜在平台，为探索低维系统中的丰富物理现象铺平了道路。
{"title":"Thermoelectric transport in Weyl semimetal BaMnSb2: A first-principles study","authors":"Yubi Chen, Rongying Jin, Bolin Liao, Sai Mu","doi":"10.1103/physrevmaterials.8.085401","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.085401","url":null,"abstract":"Topological materials are often associated with exceptional thermoelectric properties. Orthorhombic <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>Ba</mi><mi>Mn</mi><msub><mi>Sb</mi><mn>2</mn></msub></mrow></math> is a topological semimetal consisting of alternating layers of Ba, Sb, and MnSb. A recent experiment demonstrates that <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>Ba</mi><mi>Mn</mi><msub><mi>Sb</mi><mn>2</mn></msub></mrow></math> has a low thermal conductivity and modest thermopower, promising as a thermoelectric material. Through first-principles calculations with Coulomb repulsion and spin-orbit coupling included, we studied the electronic structure, phononic structure, and thermoelectric transport properties of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>Ba</mi><mi>Mn</mi><msub><mi>Sb</mi><mn>2</mn></msub></mrow></math> in depth. We find that <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>Ba</mi><mi>Mn</mi><msub><mi>Sb</mi><mn>2</mn></msub></mrow></math> exhibits a low lattice thermal conductivity, owing to the scattering of the acoustic phonons with low-frequency optical modes. Using the linearized Boltzmann transport theory with a constant relaxation time approximation, the thermopower is further calculated and an intriguing goniopolar transport behavior, which is associated with both <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>n</mi></math>-type and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>p</mi></math>-type conduction along separate transport directions simultaneously, is observed. We propose that the figure of merit can be enhanced via doping in which electrical conductivity is increased while the thermopower remains undiminished. <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>Ba</mi><mi>Mn</mi><msub><mi>Sb</mi><mn>2</mn></msub></mrow></math> is a potential platform for elucidating complex band structure effects and topological phenomena, paving the way to explore rich physics in low-dimensional systems.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"61 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142206150","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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