Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session Q66: Magnetic, Ferroelectric and Polar: Films and InterfacesRecordings Available
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Chair: Seongshik Oh, Rutgers University Room: Hyatt Regency Hotel -Grant Park D |
Wednesday, March 16, 2022 3:00PM - 3:12PM |
Q66.00001: Air-stable tetragonal antiferromagnetic FeTe thin films by molecular beam epitaxy Jisoo Moon, Qiang Zhou, Lian Li, Connie H Li Antiferromagnetic (AFM) materials have gained renewed attention due to recent demonstration of manipulation and detection of the magnetic state of antiferromagnets. Here we report thin film growth of AFM tetragonal FeTe on SrTiO3(001) substrates by molecular beam epitaxy (MBE). Layer-by-layer growth is verified by in situ scanning tunneling microscopy (STM), and atomic resolution imaging displays square lattices, confirming the tetragonal phase. Furthermore, tunneling spectroscopy shows metallic behavior. For Se-capped 20 monolayer FeTe films, temperature-dependent superconducting quantum interference device (SQUID) magnetometry measurements indicate the Néel temperature (TN) of about 100 K. The TN drops to 75 K after air exposure for more than a year. Electrical transport measurements reveal that majority carriers are p-type, and that the system is metallic from room temperature down to 2 K. The carrier mobility reaches >2,000 cm2/V∙s at 2 K, three orders of magnitude higher than those previously reported in this material system. The growth of high-quality wafer-scale air-stable AFM FeTe thin films opens new opportunities for studies of novel phenomena for spintronic applications. |
Wednesday, March 16, 2022 3:12PM - 3:24PM Withdrawn |
Q66.00002: Buffer layered growth of nickeline and zinc-blende MnTe on c-plane Al2O3 Deepti Jain, Hee Taek Yi, Matthew Brahlek, Xiong Yao, Seongshik Oh MnTe is a well-known polymorphic semiconductor with nickeline, zinc blende and wurtzite being its most widely studied phases. While nickeline MnTe has found application in dilute magnetic semiconductors and thermoelectric materials, the zinc blende and wurtzite phases are utilized in optoelectronic devices owing to their larger bandgap. So far, these films have been grown on structurally compatible substrates, via doping or by displacive transformation. We have successfully grown both nickeline and zinc blende phases on c-plane Al2O3 substrates by developing different buffer layer for the two phases. Such control over growth of MnTe could potentially lead to novel heterostructures and provide new directions for fabrication of devices. |
Wednesday, March 16, 2022 3:24PM - 3:36PM |
Q66.00003: Using anisotropic epitaxy to stabilise a low-symmetry phase in BiFeO3 with an enhanced electromechanical response. Oliver H Paull, Daniel Sando, Changsong Xu, Nagarajan Valanoor, Xuan Cheng, Yangyang Zhang, Bin Xu, Kyle Kelley, Alex DeMarco, Rama K Vasudevan, Laurent Bellaiche Piezoelectrics interconvert mechanical energy and electric charge and are widely used in actuators and sensors. The best performing materials are ferroelectrics at a morphotropic phase boundary, where several phases coexist. Switching between these phases by electric field produces a large electromechanical response. In ferroelectric BiFeO3, strain can create a morphotropic-phase-boundary-like phase mixture and thus generate large electric-field-dependent strains. However, this enhanced response occurs at localized, randomly positioned regions of the film. Here, we use epitaxial strain and orientation engineering in tandem—anisotropic epitaxy—to craft a low-symmetry phase of BiFeO3 that acts as a structural bridge between the rhombohedral-like and tetragonal-like polymorphs. Interferometric displacement sensor measurements reveal that this phase has an enhanced piezoelectric coefficient of ×2.4 compared with typical rhombohedral-like BiFeO3. Band-excitation frequency response measurements and first-principles calculations provide evidence that this phase undergoes a transition to the tetragonal-like polymorph under electric field, generating an enhanced piezoelectric response throughout the film and associated field-induced reversible strains. These results offer a route to engineer thin-film piezoelectrics with improved functionalities, with broader perspectives for other functional oxides. |
Wednesday, March 16, 2022 3:36PM - 3:48PM |
Q66.00004: Mixture of Local Moment and Itinerant Fe Magnetism in Fe3GeN Mari Tsumuraya, David J Singh The ternary iron nitride compound Fe3GeN has a tetragonal symmetry at a room temperature with a space group I4/mcm. The first-principles calculation investigates the magnetic behavior of the two different positions of Fe atoms. |
Wednesday, March 16, 2022 3:48PM - 4:00PM |
Q66.00005: Signatures of Rashba and Rashba-Edelstein effect in charge and spin transport properties of elemental Bismuth thin films Eugene D Ark, Naween Anand, Deshun Hong, Changjiang Liu, Vidya Madhavan, Anand Bhattacharya The (111) surface of elemental bismuth has been associated with a large Rashba spin-orbit coupling that can lead to significant spin polarization of carriers, and also conversion of charge currents to spin-accumulation via the Rashba-Edelstein (RE) effect. However, direct evidence for the RE effect in transport properties has been lacking. Using magnetotransport measurements, we present evidence for high-mobility, two-dimensional surface states in epitaxially grown Bi (111) thin films, that begin to dominate charge transport below a characteristic temperature Ts ~ 100 K. We also conduct spin-torque ferromagnetic resonance (ST-FMR) measurements on Bi (111)/Permalloy bilayers. We observe a significant increase in the damping like torque below Ts, consistent with enhanced spin transport across the Bi/Permalloy interface. We relate our observations to the spin-momentum locking at Bi (111) surfaces. |
Wednesday, March 16, 2022 4:00PM - 4:12PM |
Q66.00006: Thickness dependence of magnetic anisotropy and anomalous Hall effect in hydrogenated PdCoO2 films Gaurab Rimal, Yiting Liu, Haoming Yu, Shriram Ramanathan, Matthew Brahlek, Seongshik Oh The metallic delafossite PdCoO2, which is among the most conductive materials, is an outstanding candidate for studying the electronic behaviors of layered triangular lattice oxides. It was previously found that a simple hydrogen annealing procedure reduces this oxide, which leads to the emergence of magnetism with perpendicular magnetic anisotropy (PMA) and exhibits sign-tunability of anomalous Hall effect (AHE). We show that this effect is dependent on the film thickness. Beyond a critical thickness of 25 nm, the PMA changes to in-plane anisotropy and the sign-tunability of AHE is also inhibited. Extensive analysis of longitudinal and Hall resistance suggests that microscopic changes induced by hydrogen annealing leads to the changes in AHE. |
Wednesday, March 16, 2022 4:12PM - 4:24PM |
Q66.00007: Weak-antilocalization and superconductivity at the (111) KTaO3 Interfaces Athby H Al-Tawhid The intersection of two-dimensional superconductivity and topologically nontrivial states hosts a wide range of quantum phenomena, including Majorana fermions. Here, we report on the observation of two-dimensional superconductivity and weak anti-localization at the TiOx/KTaO3(111) interfaces. A remnant, saturating resistance persists below the transition temperature as superconducting puddles fail to reach phase coherence. Signatures of weak anti-localization are observed below the superconducting transition, suggesting the coexistence of superconductivity and weak anti-localization. The superconducting interfaces show roughly one order of magnitude larger weak anti-localization correction, compared to non-superconducting interfaces, alluding to the presence of topologically nontrivial states in these interfaces. |
Wednesday, March 16, 2022 4:24PM - 4:36PM |
Q66.00008: Ionic-liquid-gating study of SrTiO3 and KTaO3 Chiou Yang Tan, Issam Khayr, Tathamay Basu, Sajna Hameed, Damjan Pelc, Martin Greven Strontium titanate (SrTiO3, STO) and potassium tantalate (KTaO3, KTO) are insulators, quantum paraelectrics, and they both have the cubic perovskite structure at room temperature [1,2]. The charge-carrier density in these materials is usually modified via substitutional- or oxygen-vacancy doping. An alternative approach is ionic-liquid gating, which involves the use of an electric field to modify the carrier density in a material; an electric double layer forms between the sample and the ionic liquid when a gate voltage is applied between them [3]. Here we report on a systematic investigation of the gating-induced insulator-metal transition and temperature-dependent resistivity of STO and KTO. |
Wednesday, March 16, 2022 4:36PM - 4:48PM |
Q66.00009: Shubnikov-de Haas Oscillations into the Quantum Limit in Two-Dimensional Electron Systems at SrTiO3 (111) Interfaces Ziqiao Wang, Autumn Heltman, Shalini Kumari, Lunhui Hu, Zhu Lin, Lin Jiao, Shalinee Chikara, Alexey Suslov, John Singleton, Fedor Balakirev, Chaoxing Liu, Qi Li Transition metal oxides in the (111) orientation have been predicted to harbor topological phases and unconventional quantum states because of their hexagonal crystal symmetry and strong interactions between charge, spin, and orbital degrees of freedom. We report Shubnikov-de Haas oscillations into the quantum limit at magnetic fields up to 35 T and temperatures down to 300 mK in high mobility (>20,000 cm2V-1s-1) two-dimensional electron liquids at (111) oriented SrTiO3 interfaces with controllable carrier densities. Angular dependent spin splitting is observed at low Landau levels which is attributed to the interplay between the Zeeman splitting and Rashba spin-orbit coupling according to our theoretical modeling. After the system reaches the quantum limit, the temperature dependence of the resistance shows a metallic to insulating state transition with the magnetoresistance changing significantly from a primarily quadratic to a large linear field dependence. |
Wednesday, March 16, 2022 4:48PM - 5:00PM |
Q66.00010: Evidence for the Domain Wall Nature of Sketched LaAlO3/SrTiO3 Nanowires Dawei Qiu, Mengke Ha, Qing Xiao, Zhiyuan Qin, Danqing Liu, Changjian Ma, Guanglei Cheng The SrTiO3 based complex oxide interfaces host a large array of tunable properties, which can be further programmed to a nanoscale by a conductive atomic force microscope (cAFM) probe. Stemming from the STO matrix, the quantum mechanical properties of cAFM enabled devices are drastically enhanced, with the origin remaining elusive. Here we investigate electrical and thermodynamical responses in cAFM sketched nanowires and reveal abnormal behaviors at temperature of 105 K, 80 K and 40 K, which are characteristic of the polar domain walls in STO. Our evidence points to a ferroelastic domain wall nature of the cAFM nanowires, which is critical to understand the exotic correlated phenomena in cAFM devices. |
Wednesday, March 16, 2022 5:00PM - 5:12PM |
Q66.00011: Growth of oxide thin films for various medical and electronic applications Wilfrid Prellier Interest in thin film transition metal oxides is driven in part by the potential technological application of devices exploiting intriguing phenomena, i.e. oxide electronics, and in part by the novel structures and properties observed in epitaxial oxide films, using phase, strain, and interfacial engineering. However, in spite of the large number of observations and promise of epitaxial oxide thin films, most of the investigations have been focused on films on low-index commercially-available single-crystal substrates, which have limited the scope of the study, and the applications. Here, we will present how oxide thins films can be grown on different substrtaes including polycrystalline substrates, and glass tempates. Examples will given to show different applications that can be utilzed for medecine or electronics. |
Wednesday, March 16, 2022 5:12PM - 5:24PM |
Q66.00012: SrZrS3 thin films grown on different single crystal substrates by PLD Haolei Hui, Zhonghai Yu, Sen Yang, Hao Zeng Chalcogenide perovskite is an emerging class of semiconductor materials with potential applications in electronics and optoelectronics. β-SrZrS3 with a distorted perovskite structure was theoretically predicted to be a direct gap semiconductor with band gap value of ~ 2 eV. Its powder was synthesized and optical measurement confirmed the calculation results. In this work, we report the growth of β-SrZrS3 thin films on sapphire and Lanthanum aluminate (LAO) substrates, using CS2 treatment of PLD grown films. While the films on sapphire substrates are polycrystalline with random orientation, the films on ALO show strong texture, suggesting epitaxial growth. The composition and structure were verified by EDX and XRD. The PL and Uv-vis absorption measurements show the films possess a band gap of around 2.1eV. Prospects for device applications will be discussed. |
Wednesday, March 16, 2022 5:24PM - 5:36PM |
Q66.00013: Colossal linear magnetoresistance in LaTiO3thin films on SrTiO3 Teresa M Tschirner, Berengar Leikert, Marc Gabay, Kirill Miller, Fabian Hartmann, Sven Hoefling, Joseph Dufouleur, Michael Sing, Bernd Büchner, Ralf Claessen, Louis Veyrat LaTiO3, a 3d transition metal oxide, has been of interest for its prototypical Mott insulator character, and can be readily tuned by excess oxygen doping from the insulating to the metallic phase. In this study, metallic thin films of LaTiO3 of different thicknesses (3, 5 and 10u.c.) grown by pulsed laser deposition on SrTiO3 substrates are investigated and show a series of very interesting transport effects. The films show metallic behavior, high carrier densities of ~ 2x1023 cm-3 and transport mobilities of μ > 40 000cm2 /V.s at low T. Under a perpendicular magnetic field, a strong non-saturating colossal magnetoresistance (CMR) develops with amplitudes up to 6500%. Moreover, this MR is observed to be linear starting from very low field (<1T) and non-saturating up to at least 11T. This very distinct feature is compatible with the existence of low-mobility islands with a coverage of up to 88%. The presence of so many islands under magnetic field in an otherwise high mobility system at zero magnetic field, hints to a possible paramagnetic nature of the islands. On top of these findings, an in-plane anisotropic magnetoresistance (AMR) and a planar Hall effect (PHE) is observed. |
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