Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session F28: Fe-Based Superconductors: Multiple Magnetic Orders and New FrontiersFocus
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Sponsoring Units: DMP Chair: Omar Chmaissem, Northern Illinois University and Argonne National Laboratory Room: Room 220 |
Tuesday, March 7, 2023 8:00AM - 8:36AM |
F28.00001: Sequential magnetic anisotropies in LaFeAs1-xPxO uncover the hidden universality of iron-pnictide superconductors Invited Speaker: Omar Chmaissem Iron-pnictides have been at the center extensive research motivated by the unusual competition between exotic magnetic orders and unconventional superconductivity. Several magnetic states have been sporadically observed in different systems for which their microscopic origins remain the subject of intense theoretical modeling. A puzzling conundrum was understanding the role played by competing electronic and structural instabilities that lead to seemingly unrelated magnetic states. For example, a collinear spin-density-wave (SSDW) is observed in all the iron-based arsenide series, however, only hole-doped 122-type materials enable the atabilization of a rare double-Q magnetic state (charge spin density wave – CSDW) in a narrow region of the phase diagram just before the onset of superconductivity, whereas their electron-doped 122 counterparts do not! To add intrigue to an already perplexing system, a third magnetic state (spin vortex crystal – SVC) was reported to coexist with or without the SDW magnetic order in another class of hole-doped pnictides known as 1144 (CaKFe4As4). Curiously and to the best of our knowledge, not a single pnictide system was previously found to display all the three ground states. Using neutron diffraction, we have recently shown the existence of all three magnetic orders in a single-phase diagram for P-substituted LaFeAsO (1111), all of which compete strongly with superconductivity. Our observations of SDW, CSDW and SVC in the 1111, 122 and 1144 compounds uncovers a long-sought underlying generality of magnetic ordering in the iron-pnictides and the role it plays in relation to superconductivity. |
Tuesday, March 7, 2023 8:36AM - 8:48AM |
F28.00002: Interplay of Antiferromagnetic Order with Superconductivity in CaK(Fe1-xMnx)4As4 John M Wilde, Paul C Canfield, Sergey L Budko, Aashish Sapkota, YUJI FURUKAWA, Andreas Kreyssig, Qing-Ping Ding, Mingyu Xu, Wei Tian We characterize the magnetic order using NMR, Mössbauer spectroscopy, and neutron diffraction data for several compositions of CaK(Fe1-xMnx)4As4. The magnetic order is antiferromagnetic and consistent with the hedgehog spin vortex crystal (hSVC) magnetic moment motif which has previously been found for Ni-doped CaKFe4As4. The hSVC state is characterized by the stripe-type propagation vectors (π, 0) and (0, π) just as in the doped 122 compounds. The hSVC state preserves tetragonal symmetry about the Fe site, and only this SVC motif with simple AFM stacking along c is consistent with all our observations. The Mn-doped 1144 compound coexists with superconductivity, but unlike several 122 compounds the ordered magnetic moment is not observed to decrease as the superconducting order parameter develops. In addition, with measurements of TN < TC, we infer a possible quantum phase transition into the AFM state at approximatively x=0.10. |
Tuesday, March 7, 2023 8:48AM - 9:00AM |
F28.00003: Correlations in the Fe-Chalcogenide Semiconductor K5Fe4Ag6Te10 Nathan Giles-Donovan, Youzhe Chen, Shan Wu, Songxue Chi, Henyang Zhong, Xingye Lu, Yu Song, Robert J Birgeneau Unconventional superconductors such as Fe pnictides and chalcogenides exemplify systems where the interplay between multiple degrees of freedom results in a rich phase diagram. This includes superconductivity, antiferromagnetism, and nematicity and understanding these intertwined phases remains an open question. Here we present a study of K5Fe4Ag6Te10 (KFAT) which displays both nematic and magnetic order, as in Fe-based superconductors, but is a semiconductor with a relatively large magnetic moment which allows critical scattering to be probed reliably and accurately in 3d using neutrons. KFAT displays a superstructure which orders with an incommensurate wavevector. We report neutron diffraction and critical scattering at this incommensurate position allowing the magnetic correlation length to be extracted and the phase transition to be characterized. Links to nematic ordering and correlations will be explored. This provides insight into the microscopic mechanisms in these novel materials not able to be probed accurately in other Fe pnictides due to inherently small magnetic moments. |
Tuesday, March 7, 2023 9:00AM - 9:12AM |
F28.00004: Obstruction to superconducting pairing from Dirac monopoles in iron-based superconductors Shouvik Sur, Chandan Setty, Qimiao Si Iron based superconductors (FeSCs) are known to exhibit intriguing topological properties such as surface states, hinge modes and Majorana zero-modes. For clues to the origin of these properties, recent experiments [1, 2] have suggested the role of the parent state being a doped Dirac semimetal. |
Tuesday, March 7, 2023 9:12AM - 9:24AM |
F28.00005: The role of structural disorder on the electronic nematicity of iron-based superconductors William J Meese, Thomas Vojta, Rafael M Fernandes Electronic nematicity is a key ingredient for the unconventional superconductivity observed in iron-based superconductors. Thus, elucidating its evolution in the phase diagram is crucial for a complete understanding of these materials. Regardless of the microscopic mechanism at play, the electronic nematic instability always triggers a structural tetragonal-to-orthorhombic phase transition, reflecting the fact that shear strain acts as a conjugate nematic field. An important consequence of this nemato-elastic coupling is that any type of lattice disorder, such as dislocations and vacancies, will strongly affect the nematic phase by introducing local strains. While it is common to model them as random uncorrelated nematic fields, the distribution of local strains in a crystal is correlated and anisotropic. Additionally, since the nematic order is a vestige of the stripe-magnetic order, structural disorder creates non-trivial correlations between these two intertwined degrees of freedom. In this talk, we use Monte Carlo simulations to investigate models that capture these effects, going beyond a description in terms of the random-field Ising model. We discuss experimental manifestations of these effects and their impact on the nematic phase of iron-based superconductors. |
Tuesday, March 7, 2023 9:24AM - 9:36AM |
F28.00006: An emergent quasi-2D metallic state derived from the Mott insulator framework Jiunn-Yuan Lin Recent quasi-2D systems with judicious exploitation of the atomic monolayer or few-layer architecture exhibit unprecedented physical properties that challenge the conventional wisdom on the condensed matter physics. Here we show that the infinite layer SrCuO2 (SCO), a topical cuprate Mott insulator in the bulk form, can manifest an unexpected metallic state in the quasi-2D limit when SCO is grown on TiO2-terminated SrTiO3 (STO) substrates. The sheet resistance does not conform to Landau’s Fermi liquid paradigm. Hard x-ray core-level photoemission spectra demonstrateds a definiteive Fermi level that resembles the hole doped metal, and the soft x-ray absorption spectroscopy revealeds features analogous to those of a doped Mott insulator. The hole doping does not occur at the interfaces between SCO and STO; instead it comes from the transient layers between the chain-type and planar-type structures within the SCO sector. The present work reveals a novel metallic state in the infinite layer SCO and invites further exploration to elucidate the spatial extent of this state. |
Tuesday, March 7, 2023 9:36AM - 9:48AM |
F28.00007: Evolution of the Infinite Layer Superconducting Phase from the Perovskite Phase Ariando Ariando, Saurav Prakash, Lin Er Chow, Shou Xuan Yap, Zhaoyang Luo The recent experimental report of elusive superconductivity in the infinite-layer nickelates has renewed interest in the field of high-Tc superconductors. Using soft-chemistry topotactic reduction method on doped perovskite nickelate thin films (using CaH2), apical oxygen was successfully removed, resulting in the infinite layer superconducting phase. This process has not been understood well, and has been the source of irreproducibility in the field. The reported reduction parameters are mostly an estimate. Also, very little is understood about the intermediate states during the reduction. We have used a specially designed set up to perform in situ electrical measurements on the sample whilst the reduction is happening. We have found that the perovskite phase gets reduced to the superconducting phase through a very stable insulating intermediate state. The evolution and characteristics of the infinite layer from the perovskite through the various intermediate phases will be presented. |
Tuesday, March 7, 2023 9:48AM - 10:00AM |
F28.00008: Orbital-selective Mott phase from a dehybridization in a multiorbital Hubbard model Fang Xie, Haoyu Hu, Lei Chen, Jian-Xin Zhu, Rong Yu, Qimiao Si In multi-orbital systems, certain orbitals can become Mott localized, leading to an orbital-selective Mott phase (OSMP) that is of considerable current interest in the field of iron-based superconductors. Here, we consider the OSMP in the presence of an inter-orbital hopping term. The stability of the OSMP against an interorbital has been demonstrated using an auxiliary spin method [1,2,3], but has yet to be shown in methods based on the dynamical mean field theory [4]. |
Tuesday, March 7, 2023 10:00AM - 10:12AM |
F28.00009: Nematicity in iron-based superconductors: emergent symmetry at transitions between composite electronic orders Yiming Wang, Rong Yu, Changle Liu, Jianda Wu, Qimiao Si The phase diagram of iron-based superconductors contains various electronic orders, which are intimately connected with the superconducting phase. Among the electronic states are nematic and related composite electronic orders. Here we analyze the fluctuations of one type of orders in the other. This analysis leads to an emergent U(1) symmetry at the first-order transition between a nematic phase and a C4-symmetric charge-ordered phase. We also discuss this emergent symmetry in terms of certain hidden algebra that links the different orders. The enriched continuous symmetry leads to a Goldstone mode at the transition and causes softening of excitations in the nematic and charge sectors when the system is tuned towards the transition. We address the experimental means to probe these effects and discuss the implications of our results for the iron-based superconductors and other correlated systems. |
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