2D Materials最新文献

{"title":"Pseudomagnetic fields in fully relaxed twisted bilayer and trilayer graphene","authors":"A Ceferino, F Guinea","doi":"10.1088/2053-1583/ad3b0e","DOIUrl":"https://doi.org/10.1088/2053-1583/ad3b0e","url":null,"abstract":"We present simple models to describe the in-plane and the out-of-plane lattice relaxation in twisted bilayer and symmetrically twisted trilayer graphene. Analytical results and series expansions show that for twist angles <inline-formula>\u0000<tex-math><?CDATA $thetagt 1.4^{circ}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:mi>θ</mml:mi><mml:mo>&gt;</mml:mo><mml:msup><mml:mn>1.4</mml:mn><mml:mrow><mml:mo>∘</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"tdmad3b0eieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula>, the in-plane atomic displacements lead to pseudomagnetic fields weakly dependent on <italic toggle=\"yes\">θ</italic>. In symmetrically twisted trilayer graphene, the central layer in-plane relaxation is greatly enhanced. The joint effect of the relaxation-induced pseudoscalar potentials and the associated energy difference between interlayer dimer and non-dimer pairs resulted in a significant electron–hole asymmetry both in twisted bilayer and trilayer graphene.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"10 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140834682","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}

{"title":"Dislocations in twistronic heterostructures","authors":"V V Enaldiev","doi":"10.1088/2053-1583/ad3b13","DOIUrl":"https://doi.org/10.1088/2053-1583/ad3b13","url":null,"abstract":"Long-period moiré superlattices at the twisted interface of van der Waals heterostructures relax into preferential stacking domains separated by dislocation networks. Here, we develop a mesoscale theory for dislocations in networks formed in twistronic bilayers with parallel (P) and antiparallel (AP) alignment of unit cells across the twisted interface. For P bilayers we find an exact analytical displacement field across partial dislocations and determine analytic dependences of energy per unit length and width on the orientation and microscopic model parameters. For AP bilayers we formulate a semi-analytical approximation for displacement fields across perfect dislocations, establishing parametric dependences for their widths and energies per unit length. In addition, we find regions in the parametric space of crystal thicknesses and Moiré periods for strong and weak relaxation of the Moiré pattern in multilayered twistronic heterostructures.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"6 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2024-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140798318","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}

{"title":"Goodenough–Kanamori–Anderson high-temperature ferromagnetism in tetragonal transition-metal xenes","authors":"U Yorulmaz, D Šabani, C Sevik and M V Milošević","doi":"10.1088/2053-1583/ad3e08","DOIUrl":"https://doi.org/10.1088/2053-1583/ad3e08","url":null,"abstract":"Seminal Goodenough–Kanamori–Anderson (GKA) rules provide an inceptive understanding of the superexchange interaction of two magnetic metal ions bridged with an anion, and suggest fostered ferromagnetic interaction for orthogonal bridging bonds. However, there are no examples of two-dimensional (2D) materials with structure that optimizes the GKA arguments towards enhanced ferromagnetism and its critical temperature. Here we reveal that an ideally planar GKA ferromagnetism is indeed stable in selected tetragonal transition-metal xenes (tTMXs), with Curie temperature above 300 K found in CrC and MnC. We provide the general orbitally-resolved analysis of magnetic interactions that supports the claims and sheds light at the mechanisms dominating the magnetic exchange process in these structures. Furthermore, we propose the set of three GKA-like rules that will guarantee room temperature ferromagetnism. With recent advent of epitaxially-grown tetragonal 2D materials, our findings earmark tTMXs for facilitated spintronic and magnonic applications, or as a desirable magnetic constituent of functional 2D heterostructures.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"18 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2024-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140798322","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}

{"title":"Electrically tunable correlated domain wall network in twisted bilayer graphene","authors":"Hao-Chien Wang and Chen-Hsuan Hsu","doi":"10.1088/2053-1583/ad3b11","DOIUrl":"https://doi.org/10.1088/2053-1583/ad3b11","url":null,"abstract":"We investigate the domain wall network in twisted bilayer graphene (TBG) under the influence of interlayer bias and screening effect from the layered structure. Starting from the continuum model, we analyze the low-energy domain wall modes within the moiré bilayer structure and obtain an analytic form representing charge density distributions of the two-dimensional structure. By computing the screened electron–electron interaction strengths both within and between the domain walls, we develop a bosonized model that describes the correlated domain wall network. We demonstrate that these interaction strengths can be modified through an applied interlayer bias, screening length and dielectric materials, and show how the model can be employed to investigate various properties of the domain wall network and its stability. We compute correlation functions both without and with phonons. Including electron–phonon coupling in the network, we establish phase diagrams from these correlation functions. These diagrams illustrate electrical tunability of the network between various phases, such as density wave states and superconductivity. Our findings reveal the domain wall network as a promising platform for the experimental manipulation of electron–electron interactions in low dimensions and the study of strongly correlated matter. We point out that our investigation not only enhances the understanding of domain wall modes in TBG but also has broader implications for the development of moiré devices.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"4 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140798251","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}

{"title":"Symmetry classification of 2D materials: layer groups versus space groups","authors":"Jingheng Fu, Mikael Kuisma, Ask Hjorth Larsen, Kohei Shinohara, Atsushi Togo and Kristian S Thygesen","doi":"10.1088/2053-1583/ad3e0c","DOIUrl":"https://doi.org/10.1088/2053-1583/ad3e0c","url":null,"abstract":"The symmetry of a crystal structure with a three-dimensional (3D) lattice can be classified by one of the 230 space group types. For some types of crystals, e.g. crystalline films, surfaces, or planar interfaces, it is more appropriate to assume a two-dimensional (2D) lattice. With this assumption the structure can be classified by one of the 80 layer group types. We have implemented an algorithm to determine the layer group type of a 3D structure with a 2D lattice, and applied it to more than 15 000 monolayer structures in the Computational 2D Materials Database (C2DB). We compare the classification of monolayers by layer groups and space groups, respectively. The latter is defined as the space group of the 3D bulk structure obtained by repeating the monolayer periodically in the direction perpendicular to the 2D lattice (AA-stacking). By this correspondence, nine pairs of layer group types are mapped to the same space group type due to the inability of the space group to distinguish the in-plane and out-of-plane axes. In total 18% of the monolayers in the C2DB belong to one of these layer group pairs and are thus not properly classified by the space group type. Our results show that symmetry classification of 2D materials should be based on layer groups rather than the commonly used space groups.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"28 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2024-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140798478","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}

{"title":"Effect of niobium doping on excitonic dynamics in MoSe2","authors":"Wenjie Wang, Yongsheng Wang, Jiaqi He, Zhiying Bai, Guili Li, Xiaoxian Zhang, Dawei He, Hui Zhao","doi":"10.1088/2053-1583/ad3b0d","DOIUrl":"https://doi.org/10.1088/2053-1583/ad3b0d","url":null,"abstract":"Transition metal dichalcogenides (TMDs) have emerged as attractive two-dimensional semiconductors for future electronic and optoelectronic applications. Their charge transport properties, such as conductivity and the type of charge carriers, can be effectively controlled by substitutional doping of the transition metal atoms. However, the effects of doping on the excitonic properties, particularly their dynamical properties, have been less studied. Using Nb-doped MoSe₂ as a case study, we experimentally investigate the effect of doping on excitonic dynamics in TMDs. Transient absorption measurements are used to directly compare the dynamical properties of excitons in Nb-doped MoSe₂ across monolayer, bilayer, and bulk flakes with their undoped counterparts. The exciton lifetimes in Nb-doped flakes are significantly shorter than those in their undoped counterparts. This effect is attributed to the trapping of excitons in defect states introduced by Nb impurities. These results reveal an important consequence of Nb doping on excitonic dynamics in TMDs.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"96 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2024-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140612816","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}

{"title":"Structural distortion and dynamical electron correlation driven enhanced ferromagnetism in Ni-doped two-dimensional Fe5GeTe2 beyond room temperature","authors":"Sukanya Ghosh, Soheil Ershadrad, Biplab Sanyal","doi":"10.1088/2053-1583/ad3b10","DOIUrl":"https://doi.org/10.1088/2053-1583/ad3b10","url":null,"abstract":"Achieving beyond room-temperature ferromagnetism in two-dimensional (2D) magnets is immensely desirable for spintronic applications. Fe₅GeTe₂ is an exceptional van der Waals metallic ferromagnet due to its tunable physical properties and relatively higher Curie temperature (<inline-formula>\u0000<tex-math><?CDATA $T_mathrm{C}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mi>T</mml:mi><mml:mrow><mml:mi mathvariant=\"normal\">C</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"tdmad3b10ieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula>) than other 2D magnets. Using density functional theory combined with dynamical electron correlation and Monte Carlo simulations, we find the <inline-formula>\u0000<tex-math><?CDATA $T_mathrm{C}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mi>T</mml:mi><mml:mrow><mml:mi mathvariant=\"normal\">C</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"tdmad3b10ieqn2.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> of (Fe<inline-formula>\u0000<tex-math><?CDATA $_{1-delta}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mi></mml:mi><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>δ</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"tdmad3b10ieqn3.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula>Ni<inline-formula>\u0000<tex-math><?CDATA $_{delta})_{5}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mi></mml:mi><mml:mrow><mml:mi>δ</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mo stretchy=\"false\">)</mml:mo><mml:mrow><mml:mn>5</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"tdmad3b10ieqn4.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula>GeTe₂ monolayer can increase up to ∼400 K at <inline-formula>\u0000<tex-math><?CDATA $delta sim 0.20$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:mi>δ</mml:mi><mml:mo>∼</mml:mo><mml:mn>0.20</mml:mn></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"tdmad3b10ieqn5.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> (<italic toggle=\"yes\">δ</italic>: fractional occupation). Two specific Fe sublattices are identified to be the most energetically preferred sites to host Ni. Exchange interactions between particular Fe pairs play a dominating role in controlling <inline-formula>\u0000<tex-math><?CDATA $T_mathrm{C}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mi>T</mml:mi><mml:mrow><mml:mi mathvariant=\"normal\">C</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"tdmad3b10ieqn6.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula>, influenced by the dopant-induced structural distortions. Dynamical electron correlation induces site- and orbital-specific quasi-particle mass of Fe-<italic toggle=\"yes\">d</italic> states with varying Ni concentrations. This work provides fundamen","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"63 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2024-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140612680","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}

{"title":"High spin-Chern-number insulator in α-antimonene with a hidden topological phase","authors":"Baokai Wang, Xiaoting Zhou, Yi-Chun Hung, Yen-Chuan Lin, Hsin Lin, Arun Bansil","doi":"10.1088/2053-1583/ad3136","DOIUrl":"https://doi.org/10.1088/2053-1583/ad3136","url":null,"abstract":"For a time-reversal symmetric system, the quantum spin Hall phase is assumed to be the same as the &lt;inline-formula&gt;\u0000&lt;tex-math&gt;&lt;?CDATA $mathbb{Z}_2$?&gt;&lt;/tex-math&gt;\u0000&lt;mml:math overflow=\"scroll\"&gt;&lt;mml:mrow&gt;&lt;mml:msub&gt;&lt;mml:mrow&gt;&lt;mml:mi mathvariant=\"double-struck\"&gt;Z&lt;/mml:mi&gt;&lt;/mml:mrow&gt;&lt;mml:mn&gt;2&lt;/mml:mn&gt;&lt;/mml:msub&gt;&lt;/mml:mrow&gt;&lt;/mml:math&gt;\u0000&lt;inline-graphic xlink:href=\"tdmad3136ieqn1.gif\" xlink:type=\"simple\"&gt;&lt;/inline-graphic&gt;\u0000&lt;/inline-formula&gt; topological insulator phase in the existing literature. The spin Chern number &lt;inline-formula&gt;\u0000&lt;tex-math&gt;&lt;?CDATA $mathcal{C}_s$?&gt;&lt;/tex-math&gt;\u0000&lt;mml:math overflow=\"scroll\"&gt;&lt;mml:mrow&gt;&lt;mml:msub&gt;&lt;mml:mrow&gt;&lt;mml:mi&gt;C&lt;/mml:mi&gt;&lt;/mml:mrow&gt;&lt;mml:mi&gt;s&lt;/mml:mi&gt;&lt;/mml:msub&gt;&lt;/mml:mrow&gt;&lt;/mml:math&gt;\u0000&lt;inline-graphic xlink:href=\"tdmad3136ieqn2.gif\" xlink:type=\"simple\"&gt;&lt;/inline-graphic&gt;\u0000&lt;/inline-formula&gt; is presumed to yield the same topological classification as the &lt;inline-formula&gt;\u0000&lt;tex-math&gt;&lt;?CDATA $mathbb{Z}_2$?&gt;&lt;/tex-math&gt;\u0000&lt;mml:math overflow=\"scroll\"&gt;&lt;mml:mrow&gt;&lt;mml:msub&gt;&lt;mml:mrow&gt;&lt;mml:mi mathvariant=\"double-struck\"&gt;Z&lt;/mml:mi&gt;&lt;/mml:mrow&gt;&lt;mml:mn&gt;2&lt;/mml:mn&gt;&lt;/mml:msub&gt;&lt;/mml:mrow&gt;&lt;/mml:math&gt;\u0000&lt;inline-graphic xlink:href=\"tdmad3136ieqn3.gif\" xlink:type=\"simple\"&gt;&lt;/inline-graphic&gt;\u0000&lt;/inline-formula&gt; invariant. Here, by investigating the electronic structures of monolayer &lt;italic toggle=\"yes\"&gt;α&lt;/italic&gt;-phase group V elements, we uncover the presence of a topological phase in &lt;italic toggle=\"yes\"&gt;α&lt;/italic&gt;-Sb, which can be characterized by a spin Chern number &lt;inline-formula&gt;\u0000&lt;tex-math&gt;&lt;?CDATA $mathcal{C}_s$?&gt;&lt;/tex-math&gt;\u0000&lt;mml:math overflow=\"scroll\"&gt;&lt;mml:mrow&gt;&lt;mml:msub&gt;&lt;mml:mrow&gt;&lt;mml:mi&gt;C&lt;/mml:mi&gt;&lt;/mml:mrow&gt;&lt;mml:mi&gt;s&lt;/mml:mi&gt;&lt;/mml:msub&gt;&lt;/mml:mrow&gt;&lt;/mml:math&gt;\u0000&lt;inline-graphic xlink:href=\"tdmad3136ieqn4.gif\" xlink:type=\"simple\"&gt;&lt;/inline-graphic&gt;\u0000&lt;/inline-formula&gt; = 2, even though it is &lt;inline-formula&gt;\u0000&lt;tex-math&gt;&lt;?CDATA $mathbb{Z}_2$?&gt;&lt;/tex-math&gt;\u0000&lt;mml:math overflow=\"scroll\"&gt;&lt;mml:mrow&gt;&lt;mml:msub&gt;&lt;mml:mrow&gt;&lt;mml:mi mathvariant=\"double-struck\"&gt;Z&lt;/mml:mi&gt;&lt;/mml:mrow&gt;&lt;mml:mn&gt;2&lt;/mml:mn&gt;&lt;/mml:msub&gt;&lt;/mml:mrow&gt;&lt;/mml:math&gt;\u0000&lt;inline-graphic xlink:href=\"tdmad3136ieqn5.gif\" xlink:type=\"simple\"&gt;&lt;/inline-graphic&gt;\u0000&lt;/inline-formula&gt; trivial. Although &lt;italic toggle=\"yes\"&gt;α&lt;/italic&gt;-As and Sb would thus be classified as trivial insulators within the classification schemes, we demonstrate the existence of a phase transition between &lt;italic toggle=\"yes\"&gt;α&lt;/italic&gt;-As and Sb, which is induced by band inversions at two generic &lt;italic toggle=\"yes\"&gt;k&lt;/italic&gt; points. Without spin–orbit coupling (SOC), &lt;italic toggle=\"yes\"&gt;α&lt;/italic&gt;-As is a trivial insulator, while &lt;italic toggle=\"yes\"&gt;α&lt;/italic&gt;-Sb is a Dirac semimetal with four Dirac points (DPs) located away from the high-symmetry lines. Inclusion of the SOC gaps out the DPs and induces a nontrivial Berry curvature, endowing &lt;italic toggle=\"yes\"&gt;α&lt;/italic&gt;-Sb with a high spin Chern number of &lt;inline-formula&gt;\u0000&lt;tex-math&gt;&lt;?CDATA $mathcal{C}_s$?&gt;&lt;/tex-math&gt;\u0000&lt;mml:math overflow=\"scroll\"&gt;&lt;mml:mrow&gt;&lt;mml:msub&gt;&lt;mml:mrow&gt;&lt;mml:mi&gt;C&lt;/mml:mi&gt;&lt;","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"5 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2024-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140313720","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}

{"title":"Symmetry breaking in vanadium trihalides","authors":"Luigi Camerano, Gianni Profeta","doi":"10.1088/2053-1583/ad3137","DOIUrl":"https://doi.org/10.1088/2053-1583/ad3137","url":null,"abstract":"In the light of new experimental evidence we study the insulating ground state of the <inline-formula>\u0000<tex-math><?CDATA $3d^2$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:mn>3</mml:mn><mml:msup><mml:mi>d</mml:mi><mml:mn>2</mml:mn></mml:msup></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"tdmad3137ieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula>-transition metal trihalides V<italic toggle=\"yes\">X</italic>\u0000₃ (<italic toggle=\"yes\">X</italic> = Cl, I). Based on density functional theory with the Hubbard correction we systematically show how these systems host multiple metastable states characterised by different orbital ordering and electronic behaviour. Our calculations reveal the importance of imposing a precondition in the on site <italic toggle=\"yes\">d</italic> density matrix and of considering a symmetry broken unit cell to correctly take into account the correlation effects in a mean field framework. Furthermore we ultimately found a ground state with the <inline-formula>\u0000<tex-math><?CDATA $a_{1g}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mi>a</mml:mi><mml:mrow><mml:mn>1</mml:mn><mml:mi>g</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"tdmad3137ieqn2.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> orbital occupied in a distorted V<italic toggle=\"yes\">X</italic>\u0000₆ octahedra driven by an optical phonon mode.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"2022 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2024-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140313534","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}

{"title":"Enhanced sensitivity and tunability of thermomechanical resonance near the buckling bifurcation","authors":"Hanqing Liu, Gabriele Baglioni, Carla Boix-Constant, Herre S J van der Zant, Peter G Steeneken, Gerard J Verbiest","doi":"10.1088/2053-1583/ad3133","DOIUrl":"https://doi.org/10.1088/2053-1583/ad3133","url":null,"abstract":"The high susceptibility of ultrathin two-dimensional (2D) material resonators to force and temperature makes them ideal systems for sensing applications and exploring thermomechanical coupling. Although the dynamics of these systems at high stress has been thoroughly investigated, their behavior near the buckling transition has received less attention. Here, we demonstrate that the force sensitivity and frequency tunability of 2D material resonators are significantly enhanced near the buckling bifurcation. This bifurcation is triggered by compressive displacement that we induce via thermal expansion of the devices, while measuring their dynamics via an optomechanical technique. We understand the frequency tuning of the devices through a mechanical buckling model, which allows to extract the central deflection and boundary compressive displacement of the membrane. Surprisingly, we obtain a remarkable enhancement of up to 14× the vibration amplitude attributed to a very low stiffness of the membrane at the buckling transition, as well as a high frequency tunability by temperature of more than 4.02<inline-formula>\u0000<tex-math><?CDATA $%$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:mi mathvariant=\"normal\">%</mml:mi></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"tdmad3133ieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> K⁻¹. The presented results provide insights into the effects of buckling on the dynamics of free-standing 2D materials and thereby open up opportunities for the realization of 2D resonant sensors with buckling-enhanced sensitivity.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"47 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2024-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140313536","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}