Hasan Yilmaz, Kathrin Küster, Ulrich Starke, Oliver Clemens, Masahiko Isobe, Pascal Puphal
{"title":"Realization of a classical Ruddlesden Popper type bilayer nickelate in Sr3Ni2−xAlxO7−δ with unusual Ni4+","authors":"Hasan Yilmaz, Kathrin Küster, Ulrich Starke, Oliver Clemens, Masahiko Isobe, Pascal Puphal","doi":"10.1038/s41535-024-00708-5","DOIUrl":"https://doi.org/10.1038/s41535-024-00708-5","url":null,"abstract":"<p>The discovery of 80 K superconductivity in bilayer La<sub>3</sub>Ni<sub>2</sub>O<sub>7</sub> at pressures greater than 14 GPa presents a unique opportunity to study a novel class of high-temperature superconductors. Therefore, other bilayer nickelates following the classical (<i>T</i><sup>4+</sup>) Ruddlesden-Popper (RP) series of Sr<sub>3</sub>Ni<sub>2</sub>O<sub>7</sub> would present an interesting new candidate. In this work, we study the stabilization of RP <i>n</i> = 2 phase in Sr<sub>3</sub>Ni<sub>2−<i>x</i></sub>Al<sub><i>x</i></sub>O<sub>7−<i>δ</i></sub>, via floating zone growth of crystals. With powder and single-crystal XRD, we study the stability range of the RP-type phase. Our Thermogravimetric Analysis (TGA), X-ray photoelectron spectroscopy (XPS) and gas extraction studies reveal a remarkably high oxidation state of Ni<sup>4+</sup> stabilized by chemical strain from Al. The obtained black crystals are insulating in transport and show a magnetic transition around 12 K.</p>","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"253 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142684219","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}
Hyeok Yoon, Yun Suk Eo, Jihun Park, Jarryd A. Horn, Ryan G. Dorman, Shanta R. Saha, Ian M. Hayes, Ichiro Takeuchi, Philip M. R. Brydon, Johnpierre Paglione
{"title":"Probing p-wave superconductivity in UTe2 via point-contact junctions","authors":"Hyeok Yoon, Yun Suk Eo, Jihun Park, Jarryd A. Horn, Ryan G. Dorman, Shanta R. Saha, Ian M. Hayes, Ichiro Takeuchi, Philip M. R. Brydon, Johnpierre Paglione","doi":"10.1038/s41535-024-00700-z","DOIUrl":"https://doi.org/10.1038/s41535-024-00700-z","url":null,"abstract":"<p>Uranium ditelluride (UTe<sub>2</sub>) is the strongest contender to date for a <i>p</i>-wave superconductor in bulk form. Here we perform a spectroscopic study of the ambient pressure superconducting phase of UTe<sub>2</sub>, measuring conductance through point-contact junctions formed by metallic contacts on different crystalline facets down to 250 mK and up to 18 T. Fitting a range of qualitatively varying spectra with a Blonder-Tinkham-Klapwijk (BTK) model for <i>p</i>-wave pairing, we can extract gap amplitude and interface barrier strength for each junction. We find good agreement with the data for a dominant <i>p</i><sub><i>y</i></sub>-wave gap function with amplitude 0.26 ± 0.06 meV. Our work provides spectroscopic evidence for a gap structure consistent with the proposed spin-triplet pairing in the superconducting state of UTe<sub>2</sub>.</p>","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"16 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142637131","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":"Floquet engineering of anomalous Hall effects in monolayer MoS2","authors":"Haijun Cao, Jia-Tao Sun, Sheng Meng","doi":"10.1038/s41535-024-00702-x","DOIUrl":"https://doi.org/10.1038/s41535-024-00702-x","url":null,"abstract":"<p>Light-matter interactions have emerged as a new research focus recently offering promises of unveiling novel physics and leading to applications under nonequilibrium conditions. The quantized Hall conductivities predicted by Floquet theory assuming a Fermi-Dirac distribution however deviate from experimental observations. To resolve these puzzles, we consider the effect of nonequilibrium electron occupation to study the anomalous, valley, and spin Hall effects of a prototype monolayer transition metal dichalcogenide MoS<sub>2</sub>. We find that spin Hall conductivity can be effectively suppressed approaching zero value by linearly polarized light under near resonant excitations. In contrast, it is substantially enhanced by circularly polarized light, originating from optical selection rules and topological phase transitions. Besides, the quantized anomalous Hall conductivity is much reduced if nonequilibrium occupations of Floquet bands are considered. Our study provides a novel avenue for engineering various Hall effects in two-dimensional materials using light, holding great promises for future device applications.</p>","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"44 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142637136","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}
Benjamin Geisler, Laura Fanfarillo, James J. Hamlin, Gregory R. Stewart, Richard G. Hennig, P. J. Hirschfeld
{"title":"Optical properties and electronic correlations in La3Ni2O7 bilayer nickelates under high pressure","authors":"Benjamin Geisler, Laura Fanfarillo, James J. Hamlin, Gregory R. Stewart, Richard G. Hennig, P. J. Hirschfeld","doi":"10.1038/s41535-024-00690-y","DOIUrl":"https://doi.org/10.1038/s41535-024-00690-y","url":null,"abstract":"<p>We explore the optical properties of La<sub>3</sub>Ni<sub>2</sub>O<sub>7</sub> bilayer nickelates by using density functional theory including a Coulomb repulsion term. Convincing agreement with recent experimental ambient-pressure spectra is achieved for <i>U</i> ~ 3 eV, which permits tracing the microscopic origin of the characteristic features. Simultaneous consistency with angle-resolved photoemission spectroscopy and x-ray diffraction suggests the notion of rather moderate electronic correlations in this novel high-<i>T</i><sub><i>c</i></sub> superconductor. Oxygen vacancies form predominantly at the inner apical sites and renormalize the optical spectrum quantitatively, while the released electrons are largely accommodated by a defect state. We show that the structural transition occurring under high pressure coincides with a significant enhancement of the Drude weight and a reduction of the out-of-plane interband contribution that acts as a fingerprint of the emerging hole pocket. We further calculate the optical spectra for various possible magnetic phases including spin-density waves and discuss the results in the context of experiment. Finally, we investigate the role of the 2–2 versus 1–3 layer stacking and compare the bilayer nickelate to La<sub>4</sub>Ni<sub>3</sub>O<sub>10</sub>, La<sub>3</sub>Ni<sub>2</sub>O<sub>6</sub>, and NdNiO<sub>2</sub>, unveiling general trends in the optical spectrum as a function of the formal Ni valence in Ruddlesden–Popper versus reduced Ruddlesden–Popper nickelates.</p>","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"40 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142637133","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}
Mohamed Oudah, Hsiang-Hsi Kung, Samikshya Sahu, Niclas Heinsdorf, Armin Schulz, Kai Philippi, Marta-Villa De Toro Sanchez, Yipeng Cai, Kenji Kojima, Andreas P. Schnyder, Hidenori Takagi, Bernhard Keimer, Doug A. Bonn, Alannah M. Hallas
{"title":"Discovery of superconductivity and electron-phonon drag in the non-centrosymmetric Weyl semimetal LaRhGe3","authors":"Mohamed Oudah, Hsiang-Hsi Kung, Samikshya Sahu, Niclas Heinsdorf, Armin Schulz, Kai Philippi, Marta-Villa De Toro Sanchez, Yipeng Cai, Kenji Kojima, Andreas P. Schnyder, Hidenori Takagi, Bernhard Keimer, Doug A. Bonn, Alannah M. Hallas","doi":"10.1038/s41535-024-00686-8","DOIUrl":"https://doi.org/10.1038/s41535-024-00686-8","url":null,"abstract":"<p>We present an exploration of the effect of electron-phonon coupling and broken inversion symmetry on the electronic and thermal properties of the semimetal LaRhGe<sub>3</sub>. Our transport measurements reveal evidence for electron-hole compensation at low temperatures, resulting in a large magnetoresistance of 3000% at 1.8 K and 14 T. The carrier concentration is on the order of 10<sup>21</sup>/cm<sup>3</sup> with high carrier mobilities of 2000 cm<sup>2</sup>/Vs. When coupled to our theoretical demonstration of symmetry-protected <i>almost movable</i> Weyl nodal lines, we conclude that LaRhGe<sub>3</sub> supports a Weyl semimetallic state. We discover superconductivity in this compound with a <i>T</i><sub>c</sub> of 0.39(1) K and <i>B</i><sub>c</sub>(0) of 2.2(1) mT, with evidence from specific heat and transverse-field muon spin relaxation. We find an exponential dependence in the normal state electrical resistivity below ~50 K, while Seebeck coefficient and thermal conductivity measurements each reveal a prominent peak at low temperatures, indicative of strong electron-phonon interactions. To this end, we examine the temperature-dependent Raman spectra of LaRhGe<sub>3</sub> and find that the lifetime of the lowest energy <i>A</i><sub>1</sub> phonon is dominated by phonon-electron scattering instead of anharmonic decay. We conclude that LaRhGe<sub>3</sub> has strong electron-phonon coupling in the normal state, while the superconductivity emerges from weak electron-phonon coupling. These results open up the investigation of electron-phonon interactions in the normal state of superconducting non-centrosymmetric Weyl semimetals.</p>","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"5 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2024-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142597169","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":"Pseudospins revealed through the giant dynamical Franz-Keldysh effect in massless Dirac materials","authors":"Youngjae Kim","doi":"10.1038/s41535-024-00701-y","DOIUrl":"https://doi.org/10.1038/s41535-024-00701-y","url":null,"abstract":"<p>The dynamical Franz-Keldysh effect, indicative of the transient light-matter interaction regime between quantum and classical realms, is widely recognized as an essential signature in wide bandgap condensed matter systems such as dielectrics. In this theoretical study, we applied time-resolved transient absorption spectroscopy to investigate ultrafast optical responses in graphene, a zero-bandgap system. We observed in the gate-tuned graphene that the massless Dirac materials notably enhance intraband light-driven transitions, significantly leading to the giant dynamical Franz-Keldysh effect compared to the massive Dirac materials, a wide bandgap system. In addition, employing the angle-resolved spectroscopy, it is found that the unique polarimetry orientation, i.e., perpendicular polarizations for the pump and the probe, further pronounces the optical spectra to exhibit the complete fishbone structure, reflecting quantum pseudospin natures of Dirac cones. Our findings expand the establishment of emergent transient spectroscopy frameworks into not only zero-bandgap systems but also pseudospin-mediated quantum phenomena, moving beyond dielectrics.</p>","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"33 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142597172","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}
Jialiang Tang, Ruoqian Xu, Yongcheng Ding, Xusheng Xu, Yue Ban, Man-Hong Yung, Axel Pérez-Obiol, Gloria Platero, Xi Chen
{"title":"Exploring ground states of Fermi-Hubbard model on honeycomb lattices with counterdiabaticity","authors":"Jialiang Tang, Ruoqian Xu, Yongcheng Ding, Xusheng Xu, Yue Ban, Man-Hong Yung, Axel Pérez-Obiol, Gloria Platero, Xi Chen","doi":"10.1038/s41535-024-00697-5","DOIUrl":"https://doi.org/10.1038/s41535-024-00697-5","url":null,"abstract":"<p>Exploring the ground state properties of many-body quantum systems conventionally involves adiabatic processes, alongside exact diagonalization, in the context of quantum annealing or adiabatic quantum computation. Shortcuts to adiabaticity by counter-diabatic driving serve to accelerate these processes by suppressing energy excitations. Motivated by this, we develop variational quantum algorithms incorporating the auxiliary counter-diabatic interactions, comparing them with digitized adiabatic algorithms. These algorithms are then implemented on gate-based quantum circuits to explore the ground states of the Fermi-Hubbard model on honeycomb lattices, utilizing systems with up to 26 qubits. The comparison reveals that the counter-diabatic inspired ansatz is superior to traditional Hamiltonian variational ansatz. Furthermore, the number and duration of Trotter steps are analyzed to understand and mitigate errors. Given the model’s relevance to materials in condensed matter, our study paves the way for using variational quantum algorithms with counterdiabaticity to explore quantum materials in the noisy intermediate-scale quantum era.</p>","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"62 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142597173","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}
Xiang-Rui Liu, Ming-Yuan Zhu, Yuanwen Feng, Meng Zeng, Xiao-Ming Ma, Yu-Jie Hao, Yue Dai, Rong-Hao Luo, Yu-Peng Zhu, Kohei Yamagami, Yi Liu, Shengtao Cui, Zhe Sun, Jia-Yu Liu, Yu Huang, Zhengtai Liu, Mao Ye, Dawei Shen, Bing Li, Chang Liu
{"title":"Observation of floating surface state in obstructed atomic insulator candidate NiP2","authors":"Xiang-Rui Liu, Ming-Yuan Zhu, Yuanwen Feng, Meng Zeng, Xiao-Ming Ma, Yu-Jie Hao, Yue Dai, Rong-Hao Luo, Yu-Peng Zhu, Kohei Yamagami, Yi Liu, Shengtao Cui, Zhe Sun, Jia-Yu Liu, Yu Huang, Zhengtai Liu, Mao Ye, Dawei Shen, Bing Li, Chang Liu","doi":"10.1038/s41535-024-00699-3","DOIUrl":"https://doi.org/10.1038/s41535-024-00699-3","url":null,"abstract":"<p>Obstructed atomic insulator is recently proposed as an unconventional material, in which electric charge centers localized at sites away from the atoms. A half-filling surface state would emerge at specific interfaces cutting through these charge centers and avoid intersecting any atoms. In this article, we utilized photoemission spectroscopy and density functional theory calculations to study one of the obstructed atomic insulator candidates, NiP<sub>2</sub>. A floating surface state with large effective mass that is close to the Fermi level and isolated from all bulk states is resolved on the (100) cleavage plane, implying better catalytic activity in this plane than the previously studied surfaces. Density functional theory calculation results elucidate that this floating surface state is originated from the obstructed Wannier charge centers, albeit underwent surface reconstruction. Our findings not only shed lights on the study of obstructed atomic insulators, but also provide possible route for development of new catalysts.</p>","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"4 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2024-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142566128","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}
N. D. Andriushin, J. Muller, N. S. Pavlovskii, J. Grumbach, S. Granovsky, Y. V. Tymoshenko, O. Zaharko, A. Ivanov, J. Ollivier, M. Doerr, B. Keimer, M. Mostovoy, D. S. Inosov, D. C. Peets
{"title":"Reentrant multiple-q magnetic order and a “spin meta-cholesteric” phase in Sr3Fe2O7","authors":"N. D. Andriushin, J. Muller, N. S. Pavlovskii, J. Grumbach, S. Granovsky, Y. V. Tymoshenko, O. Zaharko, A. Ivanov, J. Ollivier, M. Doerr, B. Keimer, M. Mostovoy, D. S. Inosov, D. C. Peets","doi":"10.1038/s41535-024-00698-4","DOIUrl":"https://doi.org/10.1038/s41535-024-00698-4","url":null,"abstract":"<p>Topologically nontrivial magnetic structures such as skyrmion lattices are well known in materials lacking lattice inversion symmetry, where antisymmetric exchange interactions are allowed. Only recently, topological multi-<b>q</b> magnetic textures that spontaneously break the chiral symmetry, for example, three-dimensional hedgehog lattices, were discovered in centrosymmetric compounds, where they are instead driven by frustrated interactions. Here we show that the bilayer perovskite Sr<sub>3</sub>Fe<sub>2</sub>O<sub>7</sub>, previously believed to adopt a simple single-<b>q</b> spin-helical order, hosts two distinct types of multi-<b>q</b> spin textures. Its ground state represents a novel multi-<b>q</b> spin texture with unequally intense spin modulations at the two ordering vectors. This is followed in temperature by a new “spin meta-cholesteric” phase, in which the chiral symmetry is spontaneously broken along one of the crystal directions, but the weaker orthogonal modulation melts, giving rise to intense short-range dynamical fluctuations. Shortly before the transition to the paramagnetic state, vortex-crystal order spanned by two equivalent <b>q</b> vectors emerges. This renders Sr<sub>3</sub>Fe<sub>2</sub>O<sub>7</sub> an ideal material to study transitions among multiple-<b>q</b> spin textures in a centrosymmetric host.</p>","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"7 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2024-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142490625","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}
Yu-Hang Li, Zi-Qian Zhou, Ran Cheng, Hua Jiang, X. C. Xie
{"title":"Doubled Shapiro steps in a dynamic axion insulator Josephson junction","authors":"Yu-Hang Li, Zi-Qian Zhou, Ran Cheng, Hua Jiang, X. C. Xie","doi":"10.1038/s41535-024-00692-w","DOIUrl":"https://doi.org/10.1038/s41535-024-00692-w","url":null,"abstract":"<p>Dynamic axion insulators feature a time-dependent axion field that can be induced by antiferromagnetic resonance. Here, we show that a Josephson junction incorporating this dynamic axion insulator between two superconductors exhibits striking doubled Shapiro steps wherein all odd steps are completely suppressed in the joint presence of a DC bias and a static magnetic field. The resistively shunted junction simulation confirms that these doubled Shapiro steps originate from the distinctive axion electrodynamics driven by the antiferromagnetic resonance, which thus not only furnishes a hallmark to identify the dynamic axion insulator but also provides a method to evaluate its mass term. Furthermore, the experimentally feasible differential conductance is also determined. Our work holds significant importance in condensed matter physics and materials science for understanding the dynamic axion insulator, paving the way for its further exploration and applications.</p>","PeriodicalId":19283,"journal":{"name":"npj Quantum Materials","volume":"9 1","pages":""},"PeriodicalIF":5.7,"publicationDate":"2024-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142488931","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}