npj Quantum Materials最新文献

{"title":"Gauge field dynamics in multilayer Kitaev spin liquids","authors":"Aprem P. Joy, Achim Rosch","doi":"10.1038/s41535-024-00673-z","DOIUrl":"https://doi.org/10.1038/s41535-024-00673-z","url":null,"abstract":"<p>The Kitaev spin liquid realizes an emergent static <span>({{mathbb{Z}}}_{2})</span> gauge field with vison excitations coupled to Majorana fermions. We consider Kitaev models stacked on top of each other, weakly coupled by Heisenberg interaction <span>∝</span> <i>J</i>_{<span>⊥</span>}. This inter-layer coupling breaks the integrability of the model and makes the gauge fields dynamic. Conservation laws and topology keep single visons immobile. However, an inter-layer vison pairs can hop with a hopping amplitude linear in <i>J</i>_{<span>⊥</span>} confined to the layer, but their motion is strongly influenced by the type of stacking. For AA stacking, an interlayer pair has a two-dimensional motion but for AB or ABC stacking, sheet conservation laws restrict its motion to a one-dimensional channel within the plane. For all stacking types, an intra-layer vison-pair is constrained to move out-of-plane only. Depending on the anisotropy of the Kitaev couplings <i>K</i>_<i>x</i>, <i>K</i>_<i>y</i>, <i>K</i>_<i>z</i>, the intra-layer vison pairs can display either coherent tunnelling or purely incoherent hopping. When a magnetic field opens a gap for Majorana fermions, there exist two types of intra-layer vison pairs - a bosonic and a fermionic one. Only the bosonic pair obtains a hopping rate linear in <i>J</i>_{<span>⊥</span>}. We use our results to identify the leading instabilities of the spin liquid phase induced by the inter-layer coupling.</p>","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"58 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2024-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142002779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"High-TC superconductivity in La3Ni2O7 based on the bilayer two-orbital t-J model","authors":"Zhihui Luo, Biao Lv, Meng Wang, Wéi Wú, Dao-Xin Yao","doi":"10.1038/s41535-024-00668-w","DOIUrl":"https://doi.org/10.1038/s41535-024-00668-w","url":null,"abstract":"<p>The recently discovered high-<i>T</i>_c superconductor La₃Ni₂O₇ has sparked renewed interest in unconventional superconductivity. Here we study superconductivity in pressurized La₃Ni₂O₇ based on a bilayer two-orbital <i>t</i>−<i>J</i> model, using the renormalized mean-field theory. Our results reveal a robust <i>s</i>^±-wave pairing driven by the inter-layer <span>({d}_{{z}^{2}})</span> magnetic coupling, which exhibits a transition temperature within the same order of magnitude as the experimentally observed <i>T</i>_c ~ 80 K. We establish a comprehensive superconducting phase diagram in the doping plane. Notably, the La₃Ni₂O₇ under pressure is found to be situated roughly in the optimal doping regime of the phase diagram. When the <span>({d}_{{x}^{2}-{y}^{2}})</span> orbital becomes close to half-filling, <i>d</i>-wave and <i>d</i> + <i>i</i><i>s</i> pairing can emerge from the system. We discuss the interplay between Fermi surface topology and different pairing symmetries. The stability of the <i>s</i>^±-wave pairing against Hund’s coupling and other magnetic exchange couplings is discussed.</p>","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"51 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141980978","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Excellent thermoelectric performance of Fe2NbAl alloy induced by strong crystal anharmonicity and high band degeneracy","authors":"Xianfeng Ye, Jian Yu, Shaoqiu Ke, Dong Liang, Tiantian Chen, Chengshan Liu, Wenjie Xu, Longzhou Li, Wanting Zhu, Xiaolei Nie, Ping Wei, Wenyu Zhao, Qingjie Zhang","doi":"10.1038/s41535-024-00671-1","DOIUrl":"https://doi.org/10.1038/s41535-024-00671-1","url":null,"abstract":"<p>Full-Heusler alloys with earth-abundant elements exhibit high mechanical strength and favorable electrical transport behavior, but their high intrinsic lattice thermal conductivity limits potential thermoelectric application. Here, the thermoelectric transport properties of Fe-based Full-Heusler Fe₂MAl (M = V, Nb, Ta) alloys are comprehensively investigated utilizing density functional theory. The results suggest that Fe₂NbAl exhibits exceptionally low lattice thermal conductivity due to low phonon velocities and weakly bound Nb atoms. In Fe₂NbAl, the underbonding of the Nb atoms leads large Grüneisen parameters and high anharmonic scattering rates of low-frequency acoustic phonon. Meanwhile, the high band degeneracy and large electrical conductivity lead to a maximum <i>p</i>-type power factor of 255.6 μW·K⁻²·cm⁻¹ at 900 K. The combination of low lattice thermal conductivity and favorable electrical transport properties leads a maximum <i>p</i>-type dimensionless figure of merit of 1.7. Our work indicates Fe₂NbAl, as a low-cost, environmentally friendly, is a potential high-performance <i>p</i>-type thermoelectric material.</p>","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"92 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141973794","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Majorana modes in striped two-dimensional inhomogeneous topological superconductors","authors":"Pasquale Marra, Daisuke Inotani, Takeshi Mizushima, Muneto Nitta","doi":"10.1038/s41535-024-00672-0","DOIUrl":"https://doi.org/10.1038/s41535-024-00672-0","url":null,"abstract":"<p>Majorana zero modes have gained significant interest due to their potential applications in topological quantum computing and in the realization of exotic quantum phases. These zero-energy quasiparticle excitations localize at the vortex cores of two-dimensional topological superconductors or at the ends of one-dimensional topological superconductors. Here we describe an alternative platform: a two-dimensional topological superconductor with inhomogeneous superconductivity, where Majorana modes localize at the ends of topologically nontrivial one-dimensional stripes induced by the spatial variations of the order parameter phase. In certain regimes, these Majorana modes hybridize into a single highly nonlocal state delocalized over spatially separated points, with exactly zero energy at finite system sizes and with emergent quantum-mechanical supersymmetry. We then present detailed descriptions of braiding and fusion protocols and showcase the versatility of our proposal by suggesting possible setups that can potentially lead to the realization of Yang-Lee anyons and the Sachdev-Ye-Kitaev model.</p>","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"127 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2024-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141915210","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Multiferroic quantum material Ba2Cu1−xMnxGe2O7 (0 ≤ x ≤ 1) as a potential candidate for frustrated Heisenberg antiferromagnet","authors":"Henrik Thoma, Rajesh Dutta, Vladimir Hutanu, Veronica Granata, Rosalba Fittipaldi, Qiang Zhang, Jeffrey W. Lynn, Petr Čermák, Nazir Khan, Shibabrata Nandi, Manuel Angst","doi":"10.1038/s41535-024-00665-z","DOIUrl":"https://doi.org/10.1038/s41535-024-00665-z","url":null,"abstract":"<p>Multiferroic Ba₂CuGe₂O₇ was anticipated as a potential member of the exciting group of materials hosting a skyrmion or vortex lattice because of its profound Dzyaloshinskii–Moriya interaction (DMI) and the absence of single ion anisotropy (SIA). This phase, however, could not be evidenced and instead, it exhibits a complex incommensurate antiferromagnetic (AFM) cycloidal structure. Its sister compound Ba₂MnGe₂O₇, in contrast, is characterized by a relatively strong in-plane exchange interaction that competes with a non-vanishing SIA and the weak DMI, resulting in a quasi-two-dimensional commensurate AFM structure. Considering this versatility in the magnetic interactions, a mixed solid solution of Cu and Mn in Ba₂Cu_1−<i>x</i>Mn_<i>x</i>Ge₂O₇ can hold an interesting playground for its interactive DMI and SIA depending on the mixed spin states of the transition metal ions towards the skyrmion physics. Here, we present a detailed study of the micro- and macroscopic spin structure of the Ba₂Cu₁₋_<i>x</i>Mn_<i>x</i>Ge₂O₇ solid solution series using high-resolution neutron powder diffraction techniques. We have developed a remarkably rich magnetic phase diagram as a function of the applied magnetic field and <i>x</i>, which consists of two end-line phases separated by a potentially quantum-critical phase at <i>x</i> = 0.57. An AFM conical structure at zero magnetic field is demonstrated to persist up to <i>x</i> = 0.50. Our results provide crucial information on the spin structure and magnetic properties, which are necessary for the general understanding and theoretical developments on multiferroicity in the frame of skyrmion type or frustrated AFM lattice where DMI and SIA play an important role.</p>","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"4 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2024-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141791066","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Cr doping-induced ferromagnetism in SnTe thin films","authors":"Shanshan Liu, Enze Zhang, Zihan Li, Xiaoqian Zhang, Wenqing Liu, Awadhesh Narayan, Zhi-Gang Chen, Jin Zou, Faxian Xiu","doi":"10.1038/s41535-024-00667-x","DOIUrl":"https://doi.org/10.1038/s41535-024-00667-x","url":null,"abstract":"<p>Transition-metal doped topological insulators have been widely explored since the observation of quantum anomalous Hall effect (QAHE). Subsequently, the magnetic (Pb,Sn)(Te,Se) was predicted to possibly possess a high-temperature QAHE state. However, the fundamental understanding of Cr-doping-induced ferromagnetism in this system remains unclear. Here, we report the stable ferromagnetism in the high-crystalline Cr-doped SnTe films. Upon Cr doping, the magnetoconductance unveils a crossover from weak antilocalization to weak localization. Further increasing the Cr concentration to Cr_0.17Sn_0.83Te introduces a strong ferromagnetism with a Curie temperature of ~140 K. We detected a sizable spin moment <i>m</i>_s = 2.28 ± 0.23 <i>μ</i>_B/Cr and a suppressed orbital moment <i>m</i>_l = 0.02 <i>μ</i>_B/Cr. Cr dopants prefer to substitute the Sn sites and behave as divalent cations, as indicated by the experimental results and density function theory calculations. The controllable growth of magnetic SnTe thin films provides enlightenment towards the high-temperature QAHE in magnetic TCIs for the desired dissipationless transport in electronics.</p>","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"170 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2024-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141732680","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Anomalous upper critical field in the quasicrystal superconductor Ta1.6Te","authors":"Taichi Terashima, Yuki Tokumoto, Kotaro Hamano, Takako Konoike, Naoki Kikugawa, Keiichi Edagawa","doi":"10.1038/s41535-024-00669-9","DOIUrl":"https://doi.org/10.1038/s41535-024-00669-9","url":null,"abstract":"<p>Superconductivity in quasicrystals poses a new challenge in condensed matter physics. We measured the resistance and ac magnetic susceptibility of a Ta_1.6Te dodecagonal quasicrystal, which is superconducting below <i>T</i>_<i>c</i> ~ 1 K. We show that the upper critical field increases linearly with a large slope of − 4.4 T/K with decreasing temperature down to 0.04 K, with no tendency to level off. The extrapolated zero-temperature critical field exceeds the Pauli limit by a factor of 2.3. We also observed flux-flow resistance with thermally activated behavior and an irreversibility field that is distinct from the upper critical field. We discuss these peculiarities in terms of the nonuniform superconducting gap and spin-orbit interaction in quasicrystal structures.</p>","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"6 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2024-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141730558","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 and lattice dynamics of the two-dimensional van der Waals ferromagnet CrI3","authors":"Jonghyeon Kim, Saikat Banerjee, Junghyun Kim, Minseong Lee, Suhan Son, Jangwon Kim, Taek Sun Jung, Kyung Ik Sim, Je-Geun Park, Jae Hoon Kim","doi":"10.1038/s41535-024-00666-y","DOIUrl":"https://doi.org/10.1038/s41535-024-00666-y","url":null,"abstract":"<p>Chromium tri-iodide (CrI₃) is a prototypical ferromagnetic van der Waals insulator with its genuinely two-dimensional (2D) long-range magnetic order below 45 K demonstrated recently. The underlying magnetic anisotropy has not been completely understood while both the Dzyaloshinskii-Moriya (DM) interaction and the Kitaev<span>(-Gamma)</span> type interaction have been considered as the relevant magnetic Hamiltonian. In addition, the relation between the crystal structure and the magnetic order needs to be further elucidated concerning their possible coupling in few-layer samples and in the topmost surface layers of bulk samples. Here, we investigate these issues via temperature- and magnetic field-dependent terahertz spectroscopy on bulk CrI₃ single crystals, focusing on the dynamics of ferromagnetic resonances (FMRs) and optical phonons in the terahertz (THz) region from 4 to 120 cm⁻¹ (from 0.5 to 15 meV). We narrow down the possible ranges of the interaction parameters such as the off-diagonal symmetric terms and the single-ion anisotropy. The accurate values of these parameters significantly constrain the magnitude of possible Kitaev<span>(-Gamma)</span> exchange interaction and the topological magnon gap. Moreover, the structure-magnetism relationship was critically analyzed based on the temperature- and field-dependences of two <span>({{rm{E}}}_{{rm{u}}})</span> in-plane optical phonon modes, which shows that the commonly believed structural phase diagram of CrI₃, derived from surface-preferential data, has to be seriously modified.</p>","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"27 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2024-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141730560","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Observation of the sliding phason mode of the incommensurate magnetic texture in Fe/Ir(111)","authors":"Hung-Hsiang Yang, Louise Desplat, Volodymyr P. Kravchuk, Marie Hervé, Timofey Balashov, Simon Gerber, Markus Garst, Bertrand Dupé, Wulf Wulfhekel","doi":"10.1038/s41535-024-00664-0","DOIUrl":"https://doi.org/10.1038/s41535-024-00664-0","url":null,"abstract":"<p>The nanoscopic magnetic texture forming in a monolayer of iron on the (111) surface of iridium, Fe/Ir(111), is spatially modulated and uniaxially incommensurate with respect to the crystallographic periodicities. As a consequence, a low-energy magnetic excitation is expected that corresponds to the sliding of the texture along the incommensurate direction, i.e., a phason mode, which we explicitly confirm with atomistic spin simulations. Using scanning tunneling microscopy (STM), we succeed to observe this phason mode experimentally. It can be excited by the STM tip, which leads to a random telegraph noise in the tunneling current that we attribute to the presence of two minima in the phason potential due to the presence of disorder in our sample. This provides the prospect of a floating phase in cleaner samples and, potentially, a commensurate-incommensurate transition as a function of external control parameters.</p>","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"78 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2024-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141584527","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Competition between d-wave superconductivity and magnetism in uniaxially strained Sr2RuO4","authors":"Jonas B. Profe, Sophie Beck, Dante M. Kennes, Antoine Georges, Olivier Gingras","doi":"10.1038/s41535-024-00661-3","DOIUrl":"https://doi.org/10.1038/s41535-024-00661-3","url":null,"abstract":"<p>The pairing symmetry of Sr₂RuO₄ is a long-standing fundamental question in the physics of superconducting materials with strong electronic correlations. We use the functional renormalization group to investigate the behavior of superconductivity under uniaxial strain in a two-dimensional realistic model of Sr₂RuO₄ obtained with density functional theory and incorporating the effect of spin-orbit coupling. We find a dominant <span>({d}_{{{{{rm{x}}}}}^{2}-{{{{rm{y}}}}}^{2}})</span> superconductor mostly hosted by the <i>d</i>_xy-orbital, with no other closely competing superconducting state. Within this framework, we reproduce the experimentally observed enhancement of the critical temperature under strain and propose a simple mechanism driven by the density of states to explain our findings. We also investigate the competition between superconductivity and spin-density wave ordering as a function of interaction strength. By comparing theory and experiment, we discuss constraints on a possible degenerate partner of the <span>({d}_{{{{{rm{x}}}}}^{2}-{{{{rm{y}}}}}^{2}})</span> superconducting state.</p>","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"36 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141576274","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}