Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session D71: Correlated Electronic Phenomena in Complex Oxide Thin Films and InterfacesFocus Recordings Available
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Sponsoring Units: DMP Chair: Ankit Disa, Max Planck - NYC Center for Non-equilibrium Quantum Phenomena Room: Hyatt Regency Hotel -Jackson Park C |
Monday, March 14, 2022 3:00PM - 3:12PM |
D71.00001: Energy Landscape analysis of metal-insulator transitions: theory and application to Ca$_2$RuO$_4$, RNiO$_3# and their heterostructures Andrew J Millis We present a general methodology that enables the disentanglement of the electronic and lattice contributions to the metal-insulator transition by building an energy landscape from numerical solutions of the equation of state. The methodology works with any electronic structure method that provides electronic expectation values at given atomic positions. Applying the theory to rare-earth perovskite nickelates (RNiO3) and Ruddlesden-Popper calcium ruthenates (Ca2RuO4) in bulk, heterostructure and epitaxially strained thin film forms using equation of state results from density functional plus dynamical mean field calculations we show that the electron-lattice coupling is an essential driver of the transition from the metallic to the insulating state in these materials. The methodology is used to unravel strain effects in heterostructures and interpret pump-probe experiments. |
Monday, March 14, 2022 3:12PM - 3:48PM |
D71.00002: A DFT+DMFT perspective on correlated oxide interfaces Invited Speaker: Sophie Beck Complex transition metal oxides have become a platform for materials design and discovery because they are host to a manifold of interesting physical phenomena and have a wide range of control parameters. However, the emerging phenomena at interfaces and multilayers of such materials pose a particular challenge, both theoretically and experimentally, due to the complexity of coupling different degrees of freedom at the interface. |
Monday, March 14, 2022 3:48PM - 4:00PM |
D71.00003: Electronic Transport in CaIrO3 Epitaxial Thin Films Emily R Lindgren, Sanyum Channa, Yuri Suzuki Within the complex oxide family, there has been recent interest in the study of materials that have strong spin-orbit coupling and electron-electron interactions as they hold potential for realizing topological states and other novel emergent phenomena. In the bulk, perovskite CaIrO3 is a semimetal with strong spin-orbit coupling that is reported to have electron mobility values up to 60,000 cm2/Vs and predicted to host Dirac electrons. The coexistence of high carrier mobility and strong spin-orbit coupling in CaIrO3 makes it a promising candidate for a spin sink or in spin current detection applications. In order to investigate the coexistence of high mobility and strong spin-orbit coupling in the thin film regime, we have grown perovskite CaIrO3 thin films on (001) SrTiO3 substrates via pulsed laser deposition. X-ray diffraction measurements verify epitaxial growth on the substrate. The presence of clear Laue oscillations and typical omega-rocking curve full width half maximum values of ∼0.03° indicate high crystalline quality. Our CaIrO3 films show semi-metallic behavior between 2-300K with ∂ρ/∂T <0 between 300-150K, and ∂ρ/∂T >0 down to low temperatures. Typical resistivity values for our films are on the order of a few mΩcm at room temperature, comparable to bulk values. Preliminary Hall effect measurements show electron conduction across the entire temperature range. Transport measurements in high fields out of plane to the film show a weak positive magnetoresistance at low temperatures. |
Monday, March 14, 2022 4:00PM - 4:12PM |
D71.00004: DFT-based resonant inelastic scattering study of LaCoO3, CoO and LaCoO3/LaTiO3 superlattices Alex T Lee, Sangjae Lee, Frederick J Walker, Charles H Ahn, Sohrab Ismail-Beigi Cobalt-based transition metal oxides show a variety of electronic and magnetic behaviors stemming from the multiple electronic configurations Co cations can adopt. Recently synthesized LaCoO3/LaTiO3 superlattices display strong orbital polarization [1]. Density functional theory (DFT) calculations showed that Co cations in LaCoO3 have the primarily 3+ low-spin state, while Co in the superlattices is 2+ with high-spin. The Co 2+ character is similar to CoO [2,3], but Co-O hybridization is stronger in the superlattice. |
Monday, March 14, 2022 4:12PM - 4:24PM |
D71.00005: Temperature-dependent Dielectric Properties of Hybrid MBE-Grown SrTiO3 Films Zhifei Yang, DOOYONG LEE, Jin Yue, Patricia-Lia Pop-Ghe, Shoham Sen, Richard D James, Bharat Jalan SrTiO3 (STO) is an incipient ferroelectric oxide where the onset of ferroelectric order is suppressed by quantum fluctuations. This has resulted in a giant increase in the dielectric constant from ~300 at room temperature to ~ 20,000 at low temperatures which then remained unchanged at T ≤ 30 K. While this behavior has been routinely observed in bulk STO single crystals, realization of the same in thin films has remained elusive. Low temperature dielectric constant in STO films has been limited to a few hundred or sometimes, to few thousands. Whether the low dielectric constant is due to the defects, or the interface (between film and metal electrodes) has also remained unclear. Using hybrid molecular beam epitaxy (MBE), we present detailed temperature- and frequency-dependent dielectric property measurements of STO films with a dielectric constant exceeding 20,000 in STO films. We discuss an important role of strain, point defects and interface on the measured dielectric constant. |
Monday, March 14, 2022 4:24PM - 4:36PM |
D71.00006: Orbital Aspects of Electron Correlation in the Metallic Oxide SrVO3 Lior Kornblum, Lishai Shoham, Maria Baskin, Guy Ankonina, Shay Joseph, Myung-Geun Han, Yimei Zhu, Cinthia Piamonteze, Isao H Inoue, Marcelo J Rozenberg Electron correlation is responsible for countless interesting condensed matter phenomena. Oxides with electron correlation provide an attractive testbed for many of those, where coupling between the spin, charge and lattice degrees of freedom can be found and tuned. We consider strontium vanadate (SrVO3) as a simple test case of the Mott-Hubbard type of correlated electronic structure. The material’s (relative) simplicity stems from its d1 electronic configuration and high-symmetry cubic perovskite structure. Furthermore, SrVO3 is interesting for being the metallic endmember of compounds exhibiting a filling-controlled metal-insulator transition. Recently, SrVO3 has shown promise as an earth-abundant transparent conductive oxide (TCO), a crucial element of solar cells and other optoelectronic devices. We harness advanced thin film synthesis techniques via oxide reactive molecular beam epitaxy to fabricate SrVO3 films with high structural quality, as evidenced by an electronic behavior in the low-defect regime. We combine electronic transport measurements with optical conductivity analysis, bridging between the macroscopic manifestation of the correlation and the band structure. By decoupling the contribution of defects from the electronic transport, we observe the orbital character of the electron correlation in this material. This picture, derived from a simple and clean system, might shed light on other, more complex examples. |
Monday, March 14, 2022 4:36PM - 4:48PM |
D71.00007: Disorder in Metallic Correlated-Electron SrVO3 Films Lishai Shoham, Maria Baskin, Guy Ankonina, Shay Joshef, Myung-Geun Han, Yimei Zhu, Cinthia Piamonteze, Isao H Inoue, Marcelo J Rozenberg, Lior Kornblum Correlated electron systems garner interest for their fundamental physics and their potential for novel electronics. For decades, numerous methods have been applied to vary the electron-electron interaction and study their electronic structure. SrVO3 is a correlated metal with 3d1 electron configuration and a cubic perovskite structure; therefore, it is an attractive case study for Mott-Hubbard materials. Moreover, this material system recently received considerable attention for its potential as transparent conductive oxide (TCO). In this work, we grow epitaxial SrVO3 thin films and study the impact of disorder on their electronic properties. We generate and investigate varying degrees of structural disorder, discuss its origins and pinpoint its effects in determining the transport properties. This work emphasizes the role of disorder in correlated systems, highlighting the need to decouple it for an accurate understanding of their intrinsic electronic structure. |
Monday, March 14, 2022 4:48PM - 5:24PM |
D71.00008: Electronic coupling in nickelate-based superlattices Invited Speaker: Bernat Mundet Rare earth nickelates are fascinating materials, well-known, for their metal to insulator transition (MIT) and unique antiferromagnetic ground state. Due to the lack of sizeable single crystals, heterostructures constitute the best system to study the fascinating properties of these materials [1]. Pursuant to this, we have grown superlattices made of SmNiO3 and NdNiO3 layers – two nickelates having different MIT temperatures. When these two compounds are brought together at an interface the stability of a metal-insulator phase separation can be controlled by the thickness of the individual layers with a critical length scale (Λc-MIT) below which, a single MIT occurs. Room temperature STEM-EELS confirmed that below Λc-MIT the entire structure is metallic whereas above Λc-MIT the NdNiO3 layers are metallic and the SmNiO3 layers insulating with a sharp electronic interface [2]. We propose that this behavior is controlled by the balance between the energy of the interfacial phase-boundary and the bulk phase energies [3]. |
Monday, March 14, 2022 5:24PM - 5:36PM |
D71.00009: Perturbing the bond disproportionated state in NdNiO3 KRISHNENDU PATRA, Sagar Sarkar, Priya Mahadevan
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Monday, March 14, 2022 5:36PM - 5:48PM |
D71.00010: Designing controllable cross coupling between polarization, magnetization, insulator-metal transition in oxide superlattices by multimode coupling Monirul Shaikh, Saurabh Ghosh We have employed first-principles density functional theory (DFT) calculations guided by group-theoretical analysis and demonstrated the polarization control of insulator-metal transition (IMT) in (LaFeO3)1/(CaFeO3)1 superlattice (LFO/CFO 1/1 SL). We have discovered a new charge disproportionation mode (ACD) in LFO/CFO 1/1 SL which is analogous to the A-type antiferromagnetic ordering. We found that the ACD mode couples with the tri-linear coupling (common in Pnma), QTri ~ QRQTQAFEA where QR, QT, and QAFE represent rotation, tilt, and anti-ferroelectric A-site modes respectively. The observed multimode coupling, i.e.; QM ~ QTri QACD shows a large magnetization difference associated with the ACD mode. This particular mode coupling offers polarization control of metal-to-insulator transition and magnetization. Finally, we have discussed how structural, magnetic, and electronic properties are interlinked in LFO/CFO 1/1 SL leading to the design of multifunctional materials and can be tunable via strain. |
Monday, March 14, 2022 5:48PM - 6:00PM |
D71.00011: Large Rashba Spin-Orbit Effect by Orbital Engineering at SrTiO3-based Correlated Interfaces Ganesh Ji Omar, Ariando Ariando Large spin-orbit effect is an essential element for efficient spin-orbitronics that utilizes the interplay between charge and spin degree of freedom. This spin-orbit effect is generally small in heavy-metal-based or requires large external applied voltages in complex-oxide-based heterostructures. Here, I will firstly discuss lattice and orbital polarization induced at the SrTiO3-based interfaces. Then, I will present our experimental data to show how Ti-O lattice polarization can be tuned via atomic control of orbital hybridization. This unique approach can present a large Rashba spin-orbit effect at zero applied voltages by interfacial atomic control of orbital hybridization that introduces Ti-O lattice polarization at SrTiO3-based interfaces. The observed spin-orbit effect (∼3.5×10-12eV-m) is four-fold larger than that observed in conventional SrTiO3 interfaces at zero bias voltage. The orbital hybridization and Ti-O polarization are verified through ab-initio electronic structure calculations and high-resolution atomic microscopy. Our results present a unique approach to achieve lattice polarization at SrTiO3 interfaces and open hitherto unexplored avenues of generating and controlling Rashba spin-orbit effect via orbital engineering to design next-generation spin-orbitronics. |
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