Journal of Physics: Condensed Matter最新文献

{"title":"Correlation of Dirac ordering with optical activity in AlB₂-type Dirac MBenes.","authors":"Ashish Sharma","doi":"10.1088/1361-648X/adc3e4","DOIUrl":"10.1088/1361-648X/adc3e4","url":null,"abstract":"<p><p>Using first-principles calculations, this study systematically investigates the electronic properties and optical activity of AlB₂-type Dirac MBenes alongwith their correlations. Insights from phonon-spectral calculations and<i>ab-initio</i>molecular dynamics simulations substantiates the thermally and dynamically stable character of Dirac MBenes. Electronic dispersions reveals that all Dirac MBenes exhibits finitely gapped Dirac cones (DCs) at the fermi level, while FeB₂MBene behaves as a zero-band-gap semimetal akin to graphene. Such gap in DCs is desirable and crucial for optoelectronic applications. The interplay of out-of-plane<i>d</i>_<i>xz</i>and<i>d</i>_<i>yz</i>orbitals of metal atom and hybrids in-plane dxyand dx2-y2orbitals from metal atom with p orbitals from boron atoms can be attributed to the emergence of DCs in MBenes. The calculations clearly reveal that the static dielectric constant and the energy gap within the DCs are critical factors influencing the electron-hole screening effect, consequently effecting the exciton binding energy. Further, it has been demonstrated that the exciton binding energies are consistent with predictions made by the two-dimensional (2D) Mott-Wannier model, confirming the Mott-Wannier characteristics of excitons in AlB₂-type Dirac MBenes, with the exception of partial Frenkel character in FeB₂MBene. Furthermore, it is demonstrated that Dirac MBenes exhibit a significant light absorption capacity in the near-infrared (NIR) and visible regions, with electron-hole interactions slightly modifying the optical spectral profile, making them promising for optoelectronic and photovoltaic applications. Subsequently, covariance analysis indicates that moderate energy gaps and high static dielectric constants are conducive to hosting Mott-Wannier excitons. Additionally, careful control of d-state valence electrons and hole doping can regulate the Mott-Wannier and Frenkel character of excitons in 2D Dirac materials. Thus, this comprehensive and systematic analysis of the electronic properties and optical-excitonic behavior of AlB₂-type Dirac MBenes, alongwith their correlations, enhances our understanding of this emerging family of 2D materials.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143673329","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Enhancement of ferroelectric polarization in Sm-doped BaFe_0.2Ti_0.8O₃ceramics.","authors":"Anumeet Kaur, Arkaprava Das, Trilokchand L Kumavat, Wei-Hsiang Huang, Surbhi Gupta, Joseph Vimal Vas, Chi-Liang Chen, Asokan Kandasami, Deobrat Singh, Yogesh Sonvane","doi":"10.1088/1361-648X/adc52d","DOIUrl":"10.1088/1361-648X/adc52d","url":null,"abstract":"<p><p>We show progressive enhancement in ferroelectric polarization with increasing Sm doping concentration along with retrieving tetragonality from the hexagonal paraelectric phase for Ba_1-<i>x</i>Sm<i>_x</i>Fe_0.2Ti_0.8O₃(BTO) solid solution (<i>x</i>= 0, 0.10, 0.15, 0.20). The cooperative off-centering phenomenon due to octahedral distortion promotes interpolar clustering resulting in the formation of polar nano region causing an enhancement in saturation polarization and coercive field with Sm doping. Ferroelectric domain fringes observed in scanning and transmission electron microscopic images indicate the presence of ferroelectric ordering for the highest Sm-doped compound. Formation ofSmBa∘-FeTi'defect complex results in a reduction of oxygen vacancy (V_O) defects which is observed from x-ray photoelectron spectroscopy. The reduction in V_Oimproves the domain switching by domain wall depinning and facilitates the increment in saturation polarization with Sm doping. The x-ray absorption spectra at Ti<i>L</i>_3,2edges show the increase oft2gegratio indicating enhanced Ti 3<i>d-</i>O 2<i>p</i>orbital hybridization which is supported by DFT calculation. This DFT calculation also confers that the increment in Ti 3<i>d</i>/Sm 4<i>d-</i>O 2<i>p</i>orbital hybridization further weakens the short-range repulsion between core orbitals and facilitates the enhancement of saturation polarization.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143710389","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Quantum thermoelectrics in closed circuit with non-equilibrium electrons.","authors":"Igor Volovichev, Dmytro Kadygrob","doi":"10.1088/1361-648X/adc966","DOIUrl":"https://doi.org/10.1088/1361-648X/adc966","url":null,"abstract":"<p><p>The influence of a non-equilibrium classical environment on the parameters of a quantum heat converter in a closed circuit at a given (non-zero) output power is theoretically investigated. It is shown that the non-equilibrium of the electron distribution function in metal terminals contributes to the kinetic coefficients of the linear approximation.&#xD;Analytical expressions of the Seebeck and Peltier coefficients are obtained, considering the non-equilibrium in the terminals when electric current and heat flow through the system. The influence of non-equilibrium on the theoretical power limit and efficiency of the heat engine at a fixed output power is also determined.&#xD;Closed-form solutions were obtained for the quantum bound of the heat engine output power and the theoretical limit of the heat conversion efficiency at a given output power in quantum systems with a non-equilibrium environment for certain limited cases. A spectroscopic thermoelectric method for studying quantum systems is proposed.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143788063","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Spin dynamics in linear magnetoelectric material Mn₃Ta₂O₈.","authors":"Hodaka Kikuchi, Shunsuke Hasegawa, Shinichiro Asai, Tao Hong, Kenta Kimura, Tsuyoshi Kimura, Shinichi Itoh, Takatsugu Masuda","doi":"10.1088/1361-648X/adc964","DOIUrl":"https://doi.org/10.1088/1361-648X/adc964","url":null,"abstract":"<p><p>We performed inelastic neutron scattering experiments on single crystal samples of a linear magnetoelectric material Mn₃Ta₂O₈, which exhibits a collinear antiferromagnetic order, &#xD;to reveal the spin dynamics. &#xD;Numerous modes observed in the neutron spectra were reasonably reproduced by linear spin-wave theory on the basis of the spin Hamiltonian including eight Heisenberg interactions and an easy-plane type single-ion anisotropy. The presence of strong frustration was found in the identified spin Hamiltonian.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143788277","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Frustration-induced skyrmion crystals in centrosymmetric magnets.","authors":"Hikaru Kawamura","doi":"10.1088/1361-648X/adbf5b","DOIUrl":"10.1088/1361-648X/adbf5b","url":null,"abstract":"<p><p>Recent theoretical and experimental studies on the frustration-induced skyrmion crystal (SkX) in centrosymmetric magnets are reviewed, with some emphasis on their symmetry and topological aspects. Special importance of frustration and chirality is highlighted. Theories cover the studies based on both the spin models and the electronic models. In the former, the frustrated Heisenberg models on the triangular or the square lattices interacting either via the long-range RKKY interaction or via the competing short-range exchange interactions are treated, where frustration is borne by the oscillating nature of the long-range RKKY interaction or by the competition between the shorter-range exchange interactions. Special attention is paid to the role played by the magnetic anisotropy including the dipolar interaction. The electronic models discussed are mainly the Kondo lattice model on the triangular lattice, which reduces to the RKKY Heisenberg in the weak-coupling limit. Experiments on centrosymmetric SkX-hosting magnets cover the hexagonal or trigonal magnets Gd₂PdSi₃(triangular) and Gd₃Ru₄Al₁₂(breathing kagome), and the tetragonal magnets GdRu₂Si₂and EuAl₄. Various experimental data, including magnetization or susceptibility, specific heat, Hall resistivity, resonant magnetic<i>x</i>-ray scattering, neutron scattering, Lorentz transmission electron microscopy, etc are reviewed and discussed in conjunction with the theoretical results. The nature of a variety of phases surrounding the SkX phase in the phase diagram, many of which are of multiple-<i>q</i>character, is also examined. Finally, some discussion is given about the physical origin of the centrosymmetric SkX formation, its unique features in comparison with the non-centrosymmetric SkX induced by the antisymmetric Dzaloshinskii-Moriya interaction, together with some open and challenging problems for the future.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143605266","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Ultra-wide band gap and large exciton effect in 2D ferrovalley material H-FeCl₂.","authors":"Chaobo Luo, Daxiang Chen, Zongyu Huang, Wenchao Liu, Zhihui Jiang, Landong Xiao, Gencai Guo, Xiang Qi, Xiangyang Peng","doi":"10.1088/1361-648X/adc4a8","DOIUrl":"10.1088/1361-648X/adc4a8","url":null,"abstract":"<p><p>Ferrovalley materials are valleytronic materials with intrinsic ferromagnetism, in which the presence of spontaneous valley polarization is more conducive to practical applications. The optical properties of ferrovalley are important for selectively exciting electrons at the valley. In this paper, the electronic and optical spectrum of the H-phase FeCl₂monolayer is studied using first-principles calculations as an example. We use hybrid functional HSE06 and GW₀methods with spin-orbit coupling for our calculations, the band gap of H-FeCl₂is about 3.975 and 4.072 eV at K and -K valley, which is significantly larger than that obtained by the PBE method, with a 97 meV valley splitting. It is shown that the monolayer H-FeCl₂is a ferrovalley material with an ultra-wide band gap and large intrinsic valley polarization, which has strong electronic correlation and many-body effects. Calculation of the imaginary part of the dielectric function using GW-BSE method shows that the energy corresponding to the exciton peak is 2.421 and 2.491 eV, much smaller than the GW band gap. The exciton binding energy is about 1.554 and 1.581 eV at K and -K valley, indicating a large exciton effect. And the exciton binding energy of the two valleys are unequal, with a difference of 27 meV. It is found that splitting occurs at the first exciton peak in the ferrovalley material, and the splitting value is inequivalent to the bandgap splitting at the valley, which is instructive for further research as well as application of the valleytronics.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143700814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Approaches to tunnel magnetoresistance effect with antiferromagnets.","authors":"Katsuhiro Tanaka, Takuya Nomoto, Ryotaro Arita","doi":"10.1088/1361-648X/adc05e","DOIUrl":"10.1088/1361-648X/adc05e","url":null,"abstract":"<p><p>The tunnel magnetoresistance (TMR) effect is one of the representative phenomena in spintronics. Ferromagnets, which have a net spin polarization, have been utilized for the TMR effect. Recently, by contrast, the TMR effect with antiferromagnets, which do not possess a macroscopic spin polarization, has been proposed, and also been observed in experiments. In this topical review, we discuss recent developments in the TMR effect, particularly focusing on the TMR effect with antiferromagnets. First, we review how the TMR effect can occur in antiferromagnetic tunnel junctions. The Julliere model, which has been conventionally utilized to grasp the TMR effect with ferromagnets, breaks down for the antiferromagnetic TMR effect. Instead, we see that the momentum dependent spin splitting explains the antiferromagnetic TMR effect. After that, we revisit the TMR effect from viewpoint of the local density of states (LDOS). We particularly focus on the LDOS inside the barrier, and show that the product of the LDOS will qualitatively capture the TMR effect not only in the ferromagnetic tunnel junctions but also in the ferrimagnetic and antiferromagnetic tunnel junctions. This method is expected to work usefully for designing magnetic tunnel junctions.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143625034","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Magnetic texture enabled electrical control of Dzyaloshinskii-Moriya interaction in a Weyl semimetal.","authors":"Yuriy G Semenov, Ki Wook Kim","doi":"10.1088/1361-648X/adc4a9","DOIUrl":"10.1088/1361-648X/adc4a9","url":null,"abstract":"<p><p>Purely electrical control of the Dzyaloshinskii-Moriya interaction (DMI) without any external magnetic field is explored in a magnetic Weyl semimetal (WSM). The underlying mechanism for the DMI in the WSM is the recently identified asymmetrical indirect spin-spin interaction compatible with the inversion symmetry of the structure. While the necessary imbalance in the fermion population of opposite chirality is normally achieved with non-orthogonal external electric and magnetic fields (i.e. the axial anomaly), it is found that the intrinsic axial magnetic field characteristic to an inhomogeneous magnetic texture can play the role of the magnetic field. When applied to the magnetic domain walls as specific examples, our theoretical analysis clearly illustrates that the resulting DMI is pinned by and can in turn significantly affect the wall textures. As the appearance and strength of the DMI can be solely controlled by the applied electric field, this mechanism enables electrical modulation of magnetic domains including their excitation in the WSMs. Numerical calculations highlight significant advantages of the WSM over the conventional magnetic materials in spintronic applications such as the racetrack memory.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143700803","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Experimental and theoretical investigation of strongly correlated antiferromagnet NdBiTe.","authors":"Prabuddha Kant Mishra, Shivani Kumawat, Soumyakanta Panda, Niharika Mohapatra, B K Mani, Ashok Kumar Ganguli","doi":"10.1088/1361-648X/adc231","DOIUrl":"10.1088/1361-648X/adc231","url":null,"abstract":"<p><p>The ZrSiS-class of layered materials offer interesting topological and magnetic characteristics suitable for spintronics applications. In this work, we have synthesized a polycrystalline NdBiTe using solid-state reaction technique and have examined the magnetic properties in 2-300 K temperature range using temperature and field-dependent magnetization measurements. Our magnetic and specific heat data demonstrates a long-range antiferromagnetic (AFM) ordering in the material below 4.5 K. Furthermore, our isothermal magnetization data show a signature of spin-reorientation below Neel temperature. The observed nonlinearity in inverse susceptibility vs temperature data, and a hump in specific heat in 5-20 K range, indicate the existence of crystal field splitting in the material. Our transport properties measurements show the metallic behavior with positive magnetoresistance in the temperature range of 2-300 K. The observed rise in resistivity as function of temperature below Neel temperature infers the strongly correlated fermions, which is consistent with the observed large Sommerfeld coefficient. Consistent with experimental results, our first-principles calculations predict an AFM semimetallic nature of NdBiTe. Further, our spin-orbit coupled simulations of electronic structure show a signature of weak topological nature of the material.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143657576","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Resistively detected electron spin resonance and<i>g-</i>factor in few-layer exfoliated MoS₂devices.","authors":"Chithra H Sharma, Appanna Parvangada, Lars Tiemann, Kai Rossnagel, Jens Martin, Robert H Blick","doi":"10.1088/1361-648X/adc35d","DOIUrl":"10.1088/1361-648X/adc35d","url":null,"abstract":"<p><p>MoS₂has recently emerged as a promising material for enabling quantum devices and spintronic applications. In this context, an improved physical understanding of the<i>g</i>-factor of MoS₂depending on device geometry is of great importance. Resistively detected electron spin resonance (RD-ESR) could be employed to determine the<i>g</i>-factor in micron-scale devices. However, its application and RD-ESR studies have been limited by Schottky or high-resistance contacts to MoS₂. Here, we exploit naturally<i>n</i>-doped few-layer MoS₂devices with ohmic tin (Sn) contacts that allow the electrical study of spin phenomena. Resonant excitation of electron spins and resistive detection is a possible path to exploit the spin effects in MoS₂devices. Using RD-ESR, we determine the<i>g</i>-factor of few-layer MoS₂to be ∼1.92 and observe that the<i>g</i>-factor value is independent of the charge carrier density within the limits of our measurements.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143670187","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}