Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session B08: Superconductivity: Copper Oxide - ARPESFocus
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Sponsoring Units: DCMP Chair: Daniel Dessau, University of Colorado, Boulder Room: BCEC 150 |
Monday, March 4, 2019 11:15AM - 11:27AM |
B08.00001: Three observations on the ARPES data of the cuprate superconductors - what the AF spin fluctuation can do and what it cannot
Tao Li
Renmin University of China, Beijing, China Tao Li We discuss the origin of the pseudogap phenomena in the cuprate superconductors from the perspective of the spin-Fermion model. We find that the vanishing of the pseudogap around (\pi,0) as observed recently in Pr1.3−xLa0.7CexCuO4 is consistent with the AF band folding picture of the pseudogap in the electron-doped cuprates, if we assume a strongly momentum dependent quasi-particle scattering rate on the Fermi surface[1,4]. However, we find that the pseudogap in the hole-doped cuprates is unlikely an AF band folding gap. In particular, we show that electron pairing is indispensable to eliminate the Fermi level crossing along (\pi,0)-(\pi,\pi) in a way consistent with the ARPES observation on the underdoped Bi-2201 system around T*[2,4]. Nevertheless, we find that the AF spin fluctuation in the hole-doped cuprates is responsible for the high energy hump structure, the mismatch between the hump back-bending momentum and the bare Fermi momentum, and in particular, the extremely flatness of the anti-nodal quasi-particle dispersion in the superconducting state [3,4]. |
Monday, March 4, 2019 11:27AM - 11:39AM |
B08.00002: Temperature Dependence of the Anisotropic Gap in YBa2Cu307 Guang-Lin Zhao Due to the complexity of the material structures, the experimental results for high Tc cuprates, including YBa2Cu3O7 (YBCO), are far more difficult to understand than those for conventional low Tc superconductors of simple structures. It is our view that many experimental results cannot be understood without careful first-principles calculations to include realistic electronic structures and electron-phonon (e-ph) interaction effect in these materials. We present the results of first-principles calculations for the electronic structure, e-ph interaction, and the temperature dependence of the anisotropic superconducting gap in YBCO. Our calculations show that the smaller gaps at some k-points on the Fermi surface of YBCO collapse earlier than the larger ones as the temperature increases, that leads to gapless state on the Fermi surface of YBCO even below Tc. The work was funded in part by NSF (Award # HRD 1736136 ) and ARO (Award # W911NF-15-1-0483). |
Monday, March 4, 2019 11:39AM - 11:51AM |
B08.00003: Study of the interplay between pseudogap and antiferromagnetic correlations in electron-doped cuprates via TR-ARPES Marta Zonno, Fabio Boschini, Elia Razzoli, Matteo Michiardi, Ryan P Day, Berend Zwartsenberg, Pascal Nigge, Eduardo H Da Silva Neto, Andreas Erb, Sergey Zhdanovich, Giorgio Levy, Claudio Giannetti, David J Jones, Andrea Damascelli In recent years, various angle-resolved photoemission spectroscopy (ARPES) studies focused on electron-doped cuprate superconductors to explore the similarities and differences between the two sides of the cuprates phase diagram. The pseudogap (PG) is a well-known phenomenon in the physics of high-temperature superconductors but despite numerous theoretical and experimental works, the origin of the PG in the cuprates is still under debate. Contrary to the hole-doped counterpart, antiferromagnetic (AF) correlations in the electron-doped side are stronger, offering the unique opportunity to explore the close interplay between AF, superconductivity, PG and other underlying phases. By exploiting time-resolved ARPES, we investigate the transient evolution of the low-energy density of state of the optimally doped Nd2-xCexCuO4 (NCCO, x=0.15). In particular, by studying the temperature-dependence of the PG spectral features, we demonstrate the direct relation between PG and spin correlation length and provide evidence for the primary role of AF correlations in determining the PG in electron-doped cuprates. |
Monday, March 4, 2019 11:51AM - 12:03PM |
B08.00004: Strong electron-phonon coupling in Hg1201 Ming Yi, Jayita Nayak, Zachary Anderson, Yang Tang, Martin Greven, Robert J Birgeneau, Inna Vishik Among single-layer cuprate high temperature superconductors, some materials have maximum Tc (Tc, max) near 40K while others have Tc, max near 100K, and the origin of this discrepancy is still unsettled. We present doping-dependent angle-resolved photoemission spectroscopy (ARPES) studies on HgBa2CuO4+δ (Hg1201), a single-layer cuprate with higher Tc, max, with a focus on spectral features which differ from more commonly studied single layer cuprates with lower Tc, max. Our studies indicate two different aspects of enhanced electron-phonon coupling in this system with distinct momentum dependence. |
Monday, March 4, 2019 12:03PM - 12:15PM |
B08.00005: Micro-ARPES study on the cuprate superconductor YBCO Hideaki Iwasawa, Niels Schröter, Takahiko Masui, Setsuko Tajima, Timur Kim, Moritz Hoesch Utilizing angle-resolve photoemission spectroscopy with several tens of microns spot size (micro-ARPES), we disentangled surface electronic inhomogeneity of the high-Tc cuprate superconductor YBa2Cu3O7-δ. Two surface terminations consisting of either a CuO or BaO layer are identified through a chemical-states-specified core-level intensity distribution. This enables us to perform termination-selective ARPES measurements that uncover the different charge fillings and electronic configurations depending on the surface termination. By combining the real-space and electronic information, we propose a simple model to explain the termination-dependent surface electronic reconstruction. Further, we will also present new observations of peculiar superconducting states as well as zero-energy surface states on the heavily overdoped BaO surface. |
Monday, March 4, 2019 12:15PM - 12:27PM |
B08.00006: Hidden Spin-Momentum Texture in High Tc Cuprate Superconductor Chiu-Yun Lin, Kenneth Gotlieb, Maksym Serbyn, Wentao Zhang, Christopher L Smallwood, Chris Jozwiak, Hiroshi Eisaki, Ashvin Vishwanath, Zahid Hussain, Alessandra Lanzara Spin-orbit coupling (SOC) in cuprate superconductors was not a focus of condensed matter research due to the negligible SOC value of the conducting orbitals comparing with the strong electronic correlations and its centrosymmetric crystal structure. By using spin- and angle-resolved photoemission spectroscopy, we unveiled a nontrivial spin-momentum locking pattern in Bi2Sr2CaCu2O8+x. The asymmetry of the spin-up and spin-down channel suggests the strength of SOC is in the same order of the bilayer interaction. This poses an intriguing question of how the high temperature superconducting state emerges in the presence of SOC. |
Monday, March 4, 2019 12:27PM - 12:39PM |
B08.00007: Fermi Surface Topology and Energy Gap of Heavily Underdoped Bi2212 Studied by Laser ARPES Qiang Gao, Ping Ai, Jing Liu, Cheng Hu, Guodong Liu, Xingjiang Zhou The high temperature cuprate superconductors exhibit a number of exotic properties especially in the underdoped region. Here we have carried out high resolution angle-resolved photoemission (ARPES) measurements on heavily underdoped Bi2Sr2CaCuO8 (Bi2212) superconductors by using our new laser-based ARPES system equipped with angle-resolved time-of-flight analyzer and 7 eV and 11 eV laser sources. We have synthesized high quality heavily underdoped Bi2212 single crystals with different dopings by Dy substitution of calcium and vacuum annealing. Taking advantage of our high resolution laser-ARPES, we have systematically studied the Fermi surface topology, the energy gap and the many-body effects in these heavily underdoped Bi2212. Implications of these results will be discussed. |
Monday, March 4, 2019 12:39PM - 12:51PM |
B08.00008: ARPES study of the phase diagram of superconducting BSCCO-2212 with in-situ control of surface doping Ilya K Drozdov In high-Tc cuprates, the doping of carriers into the parent Mott insulator induces unconventional superconductivity. In most materials, including the widely studied Bi-2212, the doping level p cannot be determined from the chemical composition but is rather derived from the superconducting transition temperature, Tc, which is, in turn, measured in transport, relying on the assumption that Tc dependence on doping is universal across all the cuprate families. I will present angle-resolved photoemission studies of Bi2Sr2CaCu2O8+δ single crystals cleaved and annealed in ultra-high vacuum or in ozone to reduce or increase the doping on-demand. Such in-situ annealing technique allows mapping of a wide doping range, covering not only the superconducting dome but also previously experimentally inaccessible for this material family, metallic, non-superconducting phase on the overdoped side (OD0K). Evolution of the Fermi surface with doping shows surprisingly smooth dependence across the superconducting dome while the evolution of spectroscopic features corresponding to electron-boson coupling can be continuously tracked across the entire phase diagram including the extreme overdoped region. |
Monday, March 4, 2019 12:51PM - 1:03PM |
B08.00009: Co-substitution effect on electronic structure of high-Tc cuprate superconductor, Bi2Sr2Ca(Cu1-xCox)2O8 Takeo Miyashita, Wumiti Mansuer, Hitoshi Takita, Takuya Kubo, Satoshi Ishizaka, Hideaki Iwasawa, Eike F Schwier, Kenya Shimada, Masashi Arita, Yoshinori Numata, Tatsuro Uto, Azusa Matsuda, Akihiro Ino Conventional superconductivity occurs when electron pairs are formed. However, the pairing mechanism of high-Tc superconductivity is still controversial. One may expect that experimental clues to this problem can be obtained from the behavior of superconducting gap, which represents the binding energy of an electron pair. It has previously been reported that the decrease in critical temperature, Tc, of Bi2Sr2Ca(Cu1-xCox)2O8 is proportional to Co substitution, x. Thus, it gives us a good opportunity to investigate the relation between Tc and the energy gap. Here, we report a high-resolution angel-resolved photoemission study of Bi2Sr2Ca(Cu1-xCox)2O8 by using ultraviolet laser and synchrotron radiation. Even though Tc decreases from 91 K to 55 K with 4 % substitution of Co for Cu, almost no decrease in the superconducting gap has been observed. We also measured the residual intensity within the gap as a function of temperature. We have found that the residual intensity for Co 4% samples is larger than that for pristine samples. These results suggest that the Co substitution results in reduction of the density of the electron pairs rather than the change in the binding energy of the electron pairs. |
Monday, March 4, 2019 1:03PM - 1:15PM |
B08.00010: Deviation between magnetic quantum- and Lifshitz- critical point in electron doped cuprate Pr1-xLaCexCuO4-δ Dongjoon Song, Suheon Lee, Woobin Jung, Seung-Ryoung Park, Shigeyuki Ishida, Yoshiyuki Yoshida, Hiroshi Eisaki, Kwang-Yong Choi, Changyoung Kim Since high-Tc superconductivity in copper oxide (cuprate) and Fe-based material arises near the anti-ferromagnetic (AF) order phase boundary, relation between the magnetic quantum criticality and superconductivity has attracted extensive interest. On the other hand, there is an argument in many novel superconductors that the key role in inducing superconductivity is played by Lifshitz transition which leads to Fermi surface transformation without symmetry breaking. |
Monday, March 4, 2019 1:15PM - 1:27PM |
B08.00011: Doping Evolution of Energy Gaps in Bi2Sr2CaCu2O8+δ superconductors studied by Laser-based ARPES Ping Ai, Qiang Gao, Liu Jing, Jianwei Huang, Ying Ding, Guodong Liu, Genda Gu, Xingjiang Zhou The energy gap is a key quantity in understanding the high temperature superconductivity mechanism in cuprate superconductors. We have carried out comprehensive angle-resolved photoemission (ARPES) measurements on Bi2Sr2CaCu2O8+δ (Bi2212) superconductors by utilizing our high resolution laser-based ARPES system equipped with an angle-resolved time-of-flight (ARToF) electron energy analyzer and lasers with 7 and 11 eV photon energies. With high instrumental resolution (~1 meV) and wide coverage of the momentum space, we will report detailed doping, momentum and temperature dependences of the energy gap (superconducting gap and pseudogap) in Bi2212. Implications of these results will be discussed. |
Monday, March 4, 2019 1:27PM - 1:39PM |
B08.00012: Doping evolution of kink from the contionously doped cuprate surface Yigui Zhong, Jianyu Guan, Jin Zhao, Jianhao Zhang, Zheng-Yu Weng, Genda Gu, Yujie Sun, Hong Ding We present the doping evolution of the kink dispersion at node by in-situ ARPES measuring on a continuously doped surface of Bi2212 using our recently pronounced surface treating technique of ozone/vacuum annealing [1]. We demonstrate the Fermi velocity (<5meV) decreases and the band velocity of middle energy (25~55 meV) is a constant when doping decreases. However, the band velocity beyond ~70 meV is larger and larger when goes to UD region. We propose a splendid scenario as a possibility to explain these exotic velocities of kink dispersion. We speculate there is an additional renormalisation to the Fermi velocity for the reason that the kink at ~ 10 meV comes from the coupling to boson modes like phonons. The band at middle energy constitutes by the “bared electron”, so its band velocity is independent with doping due to the rigid-band shift nature of Bi2212 [2]. However, for band dispersion higher than the ~70 meV, the electrons are fractionalized then they acquire a greater velocity. And this fractionalized effect becomes stronger when comes to more and more UD, so the band velocity becomes bigger and bigger. |
Monday, March 4, 2019 1:39PM - 1:51PM |
B08.00013: Fermi surface reconstruction in electron-doped cuprates without antiferromagnetic long-range order Junfeng He, Costel R. Rotundu, Mathias Scheurer, Yu He, Makoto Hashimoto, Kejun Xu, Yao Wang, Edwin Huang, Tao Jia, Sudi Chen, Brian Moritz, Donghui Lu, Young Sang Lee, Thomas Devereaux, Zhixun Shen Fermi surface (FS) topology is a fundamental property of metals and superconductors. In electron-doped cuprate Nd2-xCexCuO4 (NCCO), an unexpected FS reconstruction has been observed in optimal- and over-doped regime (x=0.15-0.17) by quantum oscillation measurements (QOM). This is all the more puzzling because neutron scattering suggests that the antiferromagnetic (AFM) long-range order, which is believed to reconstruct the FS, vanishes before x=0.14. To reconcile the conflict, a widely discussed external magnetic field-induced AFM long-range order in QOM explains the FS reconstruction as an extrinsic property. Here, we report angle-resolved photoemission (ARPES) evidence of FS reconstruction in optimal- and over-doped NCCO. The observed FSs are in quantitative agreement with QOM, suggesting an intrinsic FS reconstruction without field. This reconstructed FS, despite its importance as a basis to understand electron-doped cuprates, cannot be explained under the traditional scheme. We discuss the possible origin. |
Monday, March 4, 2019 1:51PM - 2:03PM |
B08.00014: In situ angle-resolved photoemission spectroscopy measurements of cuprate thin films grown by molecular beam epitaxy Zhuoyu Chen, Slavko Rebec, Tao Jia, Makoto Hashimoto, Donghui Lu, Zhixun Shen, Robert G Moore Utilizing the oxide molecular beam epitaxy (MBE) in situ connected to beam-line angle-resolved photoemission spectroscopy (ARPES) in Stanford Synchrotron Radiation Lightsource (SSRL), high-quality cuprate films grown atomic-layer-by-layer enable measurements of electronic structure tuned by various parameters, such as epitaxial strain and surface termination, which have not been possible before with bulk materials. With the in situ connected scanning tunneling microscopy (STM), we are able to further resolve electronic properties of these films in spatial dimensions. In this talk, the newest results coming from this interconnected system will be presented. |
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