Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session E47: Electronic Structure of Superconductors (Photoemission, etc.)Live
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Sponsoring Units: DCMP Chair: Sheng Ran, Washington University |
Tuesday, March 16, 2021 8:00AM - 8:12AM Live |
E47.00001: Strong-coupling mechanism of the pseudogap in small Hubbard clusters Edwin Huang In the hole-doped cuprates, the pseudogap refers to a suppression of the density of states at low energies, in the absence of superconducting long-range order. Numerous calculations of the Hubbard model show a pseudogap in the single-particle spectra, with striking similarities to photoemission and tunneling experiments on cuprates. However, no clear mechanism has been established. Here, we solve the Hubbard model on 2×2 clusters by exact diagonalization, with integration over twisted boundary conditions. A pseudogap is found in the single-particle density of states with the following characteristics: a decreasing energy scale and onset temperature for increased hole-doping, closure at a critical hole doping near 15%, absence upon electron-doping, particle-hole asymmetry indicated by the location of the gap center, and persistence in the strong-coupling limit of U/t → ∞. Studying the many-body excitation spectrum reveals that the pseudogap in single-particle spectra is due to orthogonality between bare electrons and the lowest energy excitations for U/t ≥ ∼8. |
Tuesday, March 16, 2021 8:12AM - 8:24AM Live |
E47.00002: Electronic Structure of Doped 1D Cuprate Chains Zhuoyu Chen, Yao Wang, Slavko N Rebec, Tao Jia, Makoto Hashimoto, Donghui Lu, Brian John Moritz, Robert G Moore, Thomas Devereaux, Zhixun Shen 1D cuprate chain compounds provide a unique opportunity to reveal the Hamiltonian of cuprates due to the availability of reliable theoretical solutions. However, progress has been hindered by the inability of controlled doping in these materials. We synthesize the 1D cuprate Ba2-xSrxCuO3+δ over a wide range of hole doping. Our angle-resolved photoemission spectroscopy experiments disclose the doping evolution of both the holon and spinon excitations. A prominent folding branch with an intensity far exceeding the prediction of the simple Hubbard model is identified. A quantitative theory-experiment comparison provides concrete evidence for a key missing ingredient in cuprates: a strong near-neighbor attraction. |
Tuesday, March 16, 2021 8:24AM - 8:36AM Live |
E47.00003: Signature of Tomonaga-Luttinger Liquid State in Epitaxial CoSb Nanoribbons Rui Lou, Minyinan Lei, Wenjun Ding, Wentao Yang, Xiaoyang Chen, Ran Tao, Shuyue Ding, Xiaoping Shen, Yajun Yan, Ping Cui, Haichao Xu, Rui Peng, Tong Zhang, Zhenyu Zhang, Donglai Feng Here, building upon molecular beam epitaxy, we have fabricated CoSb nanoribbons on SrTiO3(001) substrates, and investigated the electronic structures by in situ angle-resolved photoemission spectroscopy. Straight Fermi surface sheets containing multibands are observed to disperse without lateral undulations. The corresponding spectra exhibit power-law scaling with the energy and temperature in the vicinity of Fermi level, serving as a signature of Tomonaga-Luttinger liquid (TLL) state. We also reveal that this TLL system is stable against charge density wave and superconductivity down to low temperature. |
Tuesday, March 16, 2021 8:36AM - 8:48AM Live |
E47.00004: Electronic Structure across the Rare-Earth Series in Superconducting Infinite Layer Nickelates Emily Been, Wei-Sheng Lee, Harold Hwang, Yi Cui, Jan Zaanen, Thomas Devereaux, Brian John Moritz, Chunjing Jia The exciting discovery of superconductivity in oxygen-reduced monovalent nickelates has raised a new platform for the study of unconventional superconductivity, with similarities and differences to the cuprate high temperature superconductors. General trends appear in the infinite nickelates RNiO2 with rare-earths R spanning across the Lanthanides. The role of oxygen charge transfer diminishes in comparison to the cuprates, with an increased and prominent role played by rare-earth 5d electrons near the Fermi level when traversing from La to Lu. A decrease in lattice volume indicates that the magnetic exchange additionally grows, which may be favorable for superconductivity. However, compensation effects from the itinerant 5d electrons presents a close analogy to Kondo or Anderson lattices, indicating a more complex interplay between charge transfer, bandwidth renormalization, compensation, and magnetic exchange. |
Tuesday, March 16, 2021 8:48AM - 9:00AM Live |
E47.00005: Electronic structure of the all-epitaxial NbN/GaN interface Betul Pamuk, Tianlun Yu, John G Wright, Guru Khalsa, Celesta S Chang, Yury Matveyev, Thorsten Schmitt, Donglai Feng, David Anthony Muller, Huili Grace Xing, Debdeep Jena, Vladimir N. Strocov The all-epitaxial integration of the NbN superconductor with Group III-Nitride direct-band-gap semiconductors by molecular beam epitaxy has created an opportunity for scalable, integrated superconductor/semiconductor devices. Paramount to our understanding of this novel hybrid system is concrete identification of the electronic structure of both materials at their interface. While the electronic structure of III-Nitrides are well-understood, the electronic structure of NbN – an important superconductor due to its large critical temperature – has only been reported theoretically, eluding experimental verification. |
Tuesday, March 16, 2021 9:00AM - 9:12AM Live |
E47.00006: Effect of screening on high-energy phonon branches in NdBa2Cu3O7-x Leonardo Martinelli, Matteo Rossi, Riccardo Arpaia, Marco Moretti, Marco Salluzzo, Andrew Walters, Ke-jin Zhou, Lucio Braicovich, Giacomo Ghiringhelli The role of high-energy optical phonons in cuprate superconductors has recently drawn new attention. While the BCS theory evidently fails to describe the physics of these materials, phonons could assist spin fluctuations in providing the glue for Cooper pairs, significantly enhancing the critical temperature [1]. This proposal has recently been supported by the observation of a strong electron phonon coupling in some cuprates, comparable to the superexchange energy governing the magnetic properties [2,3]. Using Resonant Inelastic X-ray Scattering (RIXS) at the oxygen K-edge we have studied how the coupling between Fermi electrons and the highest-energy phonon branches is affected by the screening of free carriers in NdBa2Cu3O7-x, from the strongly under-doped to the optimally doped region. We have found a strong renormalization of bond-stretching phonons, while bond-bending ones seem to be less affected by the addition of free carriers, in agreement with the theoretical results [1]. |
Tuesday, March 16, 2021 9:12AM - 9:24AM Live |
E47.00007: Three interaction energy scales in single-layer high-Tc cuprate HgBa2CuO4+δ Sudheer Anand Sreedhar, Antonio Rossi, Jayita Nayak, Zachary Anderson, YANG TANG, Benjamin Gregory, Makoto Hashimoto, Donghui Lu, Eli Rotenberg, Robert J Birgeneau, Martin Greven, Ming Yi, Inna Vishik A major obstacle in the attempt to understand high-temperature superconductivity in cuprate superconductors has been distinguishing universal features and trends in experimental signatures from those that are materials or technique-dependent. Towards that end, we have pursued angle-resolved photoemission spectroscopy (ARPES) studies on the model cuprate HgBa2CuO4+δ (Hg1201), which has a simple crystal structure, high optimal Tc, and is well characterized by other techniques. Here, we provide an ARPES study of doping-, temperature- and momentum-dependent systematics of near-nodal dispersion anomalies in Hg1201, revealing a hierarchy of three distinct energy scales. These establish several universal phenomena connecting multiple experimental techniques with comparable spectral features across different cuprates |
Tuesday, March 16, 2021 9:24AM - 9:36AM Live |
E47.00008: First principles based theory of magnetic impurities embedded onto the surface of superconducting host, an application to FeNb(110) Bendegúz Nyári, Balazs Ujfalussy, László Szunyogh, András Lászlóffy, Kyungwha Park In this talk we describe a new, first principles based theory of |
Tuesday, March 16, 2021 9:36AM - 9:48AM Live |
E47.00009: Stability and superconductivity of compressed superhydride CeH9 with Dirac-nodal-line fermions Chongze Wang, Hyunsoo Jeon, Seho Yi, Shuyuan Liu, Jun-Hyung Cho The experimental realization of high-temperature superconductivity (SC) in compressed hydrides under megabar pressures has aroused many efforts to search for hydrides stabilized at modest pressures. For cerium hydride CeH9 recently synthesized at 80-100 GPa, our density-functional theory calculations with the Migdal-Eliashberg formalism show the presence of large anisotropic SC with a single s-wave gap spreading in the range of ~3-18 meV at T = 10 K, giving rise to a superconducting temperature of ~80 K. It is revealed that, although the Fermi surface consists of three separate sheets, their electronic states are mostly characterized by strong hybridization between Ce 4f and H 1s orbitals. All the Fermi surface sheets possess the large anisotropy of superconducting gap, which is induced by anisotropic electron-phonon coupling due to the H clathrate structure comprising three different species of H atoms. Further, we find that the nonsymmorphic S2z symmetry protects Dirac nodal surface around the Fermi energy, which is converted into Dirac nodal lines through spin-orbit coupling. Our findings offer a new platform to investigate the intriguing interplay between compressed hydrides, SC, and Dirac fermions. |
Tuesday, March 16, 2021 9:48AM - 10:00AM Live |
E47.00010: Colossal Electron-Antiferromagnetic-Magnon Coupling Induced Band Renormalization that Drives a Stoner Ferromagnetism Tianlun Yu, Rui Peng, Min Xu, Wentao Yang, Yuanhe Song, Chenhaoping Wen, Qi Yao, Xia Lou, Tong Zhang, Wei Li, Xinyuan Wei, Guang-Han Cao, Pavel Dudin, Jonathan Denlinger, Vladimir N. Strocov, Haichao Xu, Donglai Feng The interactions between electrons and antiferromagnetic magnons (AFMMs) are important for a large class of correlated materials. For example, they are the most plausible pairing glues in high-temperature superconductors, such as cuprates and iron pnictides. However, unlike electron-phonon interactions (EPIs), clear-cut observations regarding how electron-AFMM interactions (EAIs) affect the band structure are still lacking. Consequently, critical information on the EAI, such as its renormalization strength and doping dependence, remains elusive. Here we directly observe that EAI induces a kink structure in the band dispersion in Ba1-xKxMn2As2, and subsequently unveil several key characteristics of EAI. We found that the coupling constant of EAI can be as large as 6. Such a colossal renormalization from electron-boson interaction drives the system to the Stoner criteria, giving the intriguing ferromagnetic state in Ba1-xKxMn2As2. Our results expand the current knowledge of EAI, which may facilitate the further understanding of many correlated materials with similar interactions, such as high-temperature superconductors, where EAI plays a critical role. |
Tuesday, March 16, 2021 10:00AM - 10:12AM Live |
E47.00011: Ab initio description of the Bi2Sr2CaCu2O8+δ electronic structure Johannes Nokelainen, Christopher Lane, Robert Markiewicz, Bernardo Barbiellini, Aki Pulkkinen, Bahadur Singh, Jianwei Sun, Katariina Pussi, Arun Kumar Bansil Bi-based cuprate superconductors are important materials for both fundamental research and applications. As in other cuprates, the superconducting phase in the Bi compounds lies close to an antiferromagnetic phase. Our density functional theory calculations1 based on the strongly-constrained-and-appropriately-normed (SCAN) exchange correlation functional in Bi2Sr2CaCu2O8+δ reveal the persistence of magnetic moments on the copper ions for oxygen concentrations ranging from the pristine phase to the optimally hole-doped compound. We also find the existence of ferrimagnetic solutions in the heavily doped compounds, which are expected to suppress superconductivity. |
Tuesday, March 16, 2021 10:12AM - 10:24AM Live |
E47.00012: Termination-dependent electronic structure of LaFeAsO revealed by nano-ARPES Sungwon Jung, Matthew D Watson, Luke Rhodes, Daniil V. Evtushinsky, Cephise Cacho, Saicharan Aswartham, Sabine Wurmehl, Bernd Büchner, Timur Kim LaFeAsO is the parent compound of the so-called ``1111” family of iron-based superconductors – the family in which superconductivity was first discovered and in which the highest reported superconducting transition temperatures have been found. Despite its initial preeminence, its experimental electronic structure still remains an unsolved mystery. We report the experimental electronic structures as measured on both LaO and FeAs terminations using photoemission spectroscopy with a sub-micron focused beam-spot (nano-ARPES). Our data reveal very different band dispersions and core-level spectra for the different surface terminations. Our measurements are consistent with the theoretical calculations taking into account the polar charge and surface relaxations in the system [1], and give reliable assignments to the various band dispersions previously observed with a macroscopic beam spot. Our results show how nano-ARPES can now be used to study materials, and even strongly correlated electron systems, which present multiple surface terminations. |
Tuesday, March 16, 2021 10:24AM - 10:36AM On Demand |
E47.00013: Evolution of Electronic Spectral Weight in the Hubbard ladder Masanori Kohno Although the number of electronic bands is usually considered invariant in a conventional band picture, the electronic states can generally emerge, grow, and disappear as the electron density changes in strongly correlated systems. Here, the evolution of the electronic states as a function of the electron density is illustrated in the Hubbard ladder in the strong Coulomb repulsion and strong intra-rung hopping regime using the non-Abelian dynamical density-matrix renormalization group method and perturbation theory. An emergent mode in the low-electron density regime grows with the electron density and plays a significant role in the dimer Mott physics at quarter filling, whereas an originally non-interacting band at zero electron density loses the spectral weight and disappears in the Mott transition at half filling, which leads to the spin excitation of the Mott insulator. The emergence and disappearance of electronic states, which have almost been overlooked in conventional band theory and Fermi liquid theory, are particularly important in understanding of the physics around the Mott transition. |
Tuesday, March 16, 2021 10:36AM - 10:48AM On Demand |
E47.00014: Correlation between superconducting transition temperatures and physical properties Yundi Quan, Stephen Raymond Xie, Gregory Randall Stewart, James Hamlin, Peter Hirschfeld, Richard Hennig We analyze the correlation between the superconducting transition temperatures and the physical properties in the normal state, extending the previous work by Hirsch[1]. Several classes of superconductors, including the elemental superconductors, the A15 compounds and the hydrides etc, are studied and analyzed. We identify the properties that correlate with Tc in each class of superconductors. In particular, the correlation between the metallic covalent bonding and the superconducting transition temperatures is strong, which suggests a possible route for finding new high temperature superconductors by high throughput search for compounds with strong metallic covalent bonds. |
Tuesday, March 16, 2021 10:48AM - 11:00AM Not Participating |
E47.00015: When superconductivity does not fear magnetism: Insight into electronic structure of RbEuFe4As4 Timur Kim, Kirill S. Pervakov, Daniil V. Evtushinsky, Sungwon Jung, Georg Poelchen, Kurt Kummer, Vladimir A. Vlasenko, Vladimir M. Pudalov, Dimitri Roditchev, Vasily S. Stolyarov, Denis V. Vyalikh, Vladislav Borisov, Roser Valenti, Arthur Ernst, Sergey V. Eremeev, Eugene V. Chulkov In the novel stoichiometric iron-based material RbEuFe4As4 superconductivity coexists with a peculiar long range magnetic order of Eu 4f states. Using angle-resolved photoemission spectroscopy, we reveal a complex three dimensional electronic structure and compare it with density functional theory calculations. Multiple superconducting gaps were measured on various sheets of the Fermi surface. High resolution resonant photoemission spectroscopy reveals magnetic order of the Eu 4f states deep into the superconducting phase. Both the absolute values and the anisotropy of the superconducting gaps are remarkably similar to the sibling compound without Eu, indicating that Eu magnetism does not affect the pairing of electrons. A complete decoupling between Fe- and Eu-derived states was established from their evolution with temperature, thus unambiguously demonstrating that superconducting and a long range magnetic orders exist independently from each other. |
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