Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session E32: 2D Complex Oxide Devices and Devices at Oxide InterfacesFocus
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Sponsoring Units: DMP Chair: Xiaobo Yin, University of Colorado Boulder Room: 295 |
Tuesday, March 14, 2017 8:00AM - 8:36AM |
E32.00001: Synthesis and devices of complex oxides in the 2D limit Invited Speaker: Harold Hwang Recent advances in synthetic techniques have enabled the growth of complex oxides and their heterostructures with atomic-scale control. We will present new approaches to fabricating freestanding crystalline membranes, which provide the opportunity for wide-scale integration with other materials families. We will also present novel devices utilizing 2D oxide heterostuctures, with emphasis on perpendicular transport geometries. [Preview Abstract] |
Tuesday, March 14, 2017 8:36AM - 8:48AM |
E32.00002: Transport and Optoelectronic Studies of Monolayer MoS$_{2}$ Homojunctions {\&} Nanostructures Controlled By Ferroelectric Domain Patterning Zhiyong Xiao, Jinfeng Song, David Ferry, Dawei Li, Yongfeng Lu, Stephen Ducharme, Xia Hong Transition metal dichalcogenide (TMDC) monolayers such as MoS$_{2}$ have direct band gap and are promising for building nanoelectronic and optoelectronic applications. In this study, we have fabricated MoS$_{2}$ homo-junctions and nanostructures using the ferroelectric field effect combined with scanning probe controlled domain patterning. Monolayer MoS$_{2}$ field effect transistors (FETs) are fabricated on SiO$_{2}$/Si substrates, and a top gate of ferroelectric copolymer poly(vinylidene fluoride-trifluoroethylene) [PVDF-TrFE] are deposited using Langmuir-Blodgett approach. The extracted band mobility of our devices ranges from 1 to 10 cm$^{2}$V$^{-1}$s$^{-1}$ depending on the carrier density, which suggests charged impurity rather than phonon as the major scatters. Modeling the transfer characteristics in the two polarization states shows that the polarization switching does not affect the sample mobility. By patterning the top gate into half polarization up and half polarization down domains, we created a Schottky junction with a barrier height tunable by the back gate. We also create nanoscale conducting wire at the center of the channel sandwiched by two insulating regions. The optical response of the devices will be discussed. [Preview Abstract] |
Tuesday, March 14, 2017 8:48AM - 9:00AM |
E32.00003: Quantum Conductance of Graphene Field Effect Transistor on SrTiO$_{\mathrm{\mathbf{3\thinspace }}}$\textbf{Epitaxial Thin Film} Jeongmin Park, Haeyong Kang, Kyeong Tae Kang, Yoojoo Yun, Young Hee Lee, Woo Seok Choi, Dongseok Suh In this work [1], graphene field effect transistor (FET) combined with epitaxial SrTiO$_{\mathrm{3}}$ (STO) thin film of ultrahigh-k dielectric constant, was examined to check the possibility of gate-voltage scaling. Due to the atomically flat surface of thin STO film grown on Nb-doped STO single-crystal substrate, the interface between graphene and STO showed good adhesion and nonhysteretic electrical conduction as function of gate bias was observed in all temperature ranges down to 2 K. Furthermore, quantized conductance corresponding to quantum Hall state was observed up to 200 K in a magnetic field of 14 T. We noticed that the temperature-dependent shift of charge neutrality point in graphene FET is correlated with the STO's dielectric constant variation. In addition, from the analysis of the universality of quantum phenomena in graphene, effective dielectric properties of STO thin film could be deduced. Our results indicate that operating gate bias was reduced successfully by using high-k STO thin film as gate insulator, without any drawback of graphene FET performance. [1] J. Park et. al., Nano Lett., 2016, 16 (3), pp 1754--1759 [Preview Abstract] |
Tuesday, March 14, 2017 9:00AM - 9:36AM |
E32.00004: TBD - 2D Materials: Metals, Superconductors, and Correlated Materials Invited Speaker: Qi-Kun Xue |
Tuesday, March 14, 2017 9:36AM - 9:48AM |
E32.00005: Observation of transient superconductivity at LaAlO$_3$/SrTiO$_3$ interface Gopi Nath Daptary, Shelender Kumar, Pramod Kumar, Anjana Dogra, Dushyant Kumar, N. Mohanta, A. Taraphder, R. C. Budhani, Aveek Bid We present observations of a novel magnetic field assisted transient superconducting state in the two-dimensional electron gas existing at the interface of LaAlO$_3$/SrTiO$_3$ heterostructure. The observed transient superconductivity appears upon the application of a time dependent magnetic field at a temperature significantly higher than the normal superconducting T$_C$ reported previously in this material. This metastable state depends critically on the doping density in the parent compound. It appears concomitantly with a Lifshitz transition because of the interplay between ferromagnetism and superconductivity and the finite relaxation time of the in-plane magnetization. Superconductivity and magnetism are antagonistic to each other. Hence the observation of the co-existence of these two phases in the oxide heterostructures has thrown up many interesting and yet unanswered questions. Our results clearly demonstrate the inherently metastable nature of the superconducting state competing with a magnetic order in these systems. An open question in this field is the energetics of the interplay between these two competing orders and the present observation goes a long way in understanding the underlying mechanism. [Preview Abstract] |
Tuesday, March 14, 2017 9:48AM - 10:00AM |
E32.00006: Ultrahigh volumetric performance of HRGO/MnO$_{\mathrm{2}}$ hybrid all solid state flexible supercapacitors Fatima Amir, Viet Hung Pham, Evan Schultheis, James Dickerson The development of flexible energy storage devices with high energy and high power densities is critical to the emergence of wearable electronics technologies. All solid-state flexible supercapacitors, a subset of these energy storage devices, are believed to be a key solution in powering fast, flexible mobile devices. Herein, we report an easy and low cost method to fabricate bendable holey reduced graphene oxide (HRGO)/manganese oxide (MnO$_{\mathrm{2}})$ electrodes using electrophoretic deposition. Cross sectional analysis of the layers using scanning electron microscopy (SEM) showed a layer-by-layer deposition. The obtained HRGO/MnO$_{\mathrm{2}}$ supercapacitor exhibited excellent electrochemical capacitive performance within a LiClO$_{\mathrm{4\thinspace }}$gel electrolyte, with a volumetric capacitance ranging between of 608.15F/cm$^{\mathrm{3}}$ and 233.95F/cm$^{\mathrm{3}}$ for electrodes masses between 0.2mg and 2.2mg. Additionally, the assembled supercapacitors exhibited an ultrahigh volumetric energy density of 54.06Wh L$^{\mathrm{-1}}$, and a power density of 9221.82 W L$^{\mathrm{-1}}$ which is the highest value so far reported for flexible supercapacitors. [Preview Abstract] |
Tuesday, March 14, 2017 10:00AM - 10:12AM |
E32.00007: Atomic structure of single-layer FeSe/SrTiO3 interface studied by synchrotron X-ray diffraction Rui Peng, Ke Zou, Stephen Albright, Claudia Lau, Haichao Xu, Hawoong Hong, C.H. Ahn, F.J. Walker The superconducting transition temperature of single unit cell epitaxial FeSe/SrTiO$_{\mathrm{3}}$ interface (60-109 K) is significantly enhanced compared to the transition temperature in bulk FeSe (8K). It is now widely accepted that the oxide-FeSe interface plays a crucial role in enhancing the superconductivity of FeSe. One key prerequisite to understanding the role of the interface is to resolve its atomic structure and chemistry. Here we report synchrotron X-ray diffraction studies on single-layer FeSe/SrTiO$_{\mathrm{3}}$ grown and measured in ultra-high vacuum chamber. Crystal truncation rod analysis reveals a $\surd $13$\times$ $\surd $13 reconstructed SrTiO$_{\mathrm{3}}$ surface with double TiO$_{\mathrm{2}}$ termination and rumpling of SrTiO$_{\mathrm{3}}$ atoms near the interface. The details of the interface structure provide an experimental foundation towards acquiring a theoretical understanding of the interface-enhanced superconductivity in single-layer FeSe/SrTiO$_{\mathrm{3}}$. [Preview Abstract] |
Tuesday, March 14, 2017 10:12AM - 10:24AM |
E32.00008: Quantum Hall ferroelectrics and nematics in multivalley systems I. Sodemann, Zheng Zhu, Liang Fu We study broken symmetry states in multivalley quantum Hall systems whose low energy dispersions are anisotropic. Interactions tend to select states that are maximally valley polarized and have nematic character. Interestingly, in certain systems like the recently studied Bismuth (111) surfaces, the formation of these nematic states can be accompanied by appearance of an spontaneous dipole moment, leading to formation of a quantum Hall ferroelectric state. We study these states combining mean field calculations with state of the art DMRG numerical approach, and demonstrate that skyrmion-type charged excitations are extremely robust to the presence of nematic anisotropy. [Preview Abstract] |
Tuesday, March 14, 2017 10:24AM - 10:36AM |
E32.00009: Charge Density Waves and the Hidden Nesting of Purple Bronze KMo6O17 Lei Su, Vitor Pereira The layered purple bronze KMo$_6$O$_{17}$, with its robust triple CDW phase up to high temperatures, became the emblematic example of the "hidden nesting" concept. Recent experiments suggest that, on the surface layers, its CDW phase can be stabilized at much higher temperatures, and with a tenfold increase in the electronic gap in comparison with the bulk. Despite such interesting fermiology and properties, the K and Na purple bronzes remain largely unexplored systems, most particularly so at the theoretical level. We introduce the first multi-orbital effective tight-binding model to describe the effect of electron-electron interactions in this system. Upon fixing all the effective hopping parameters in the normal state against an ab-initio band structure, and with only the overall scale of the interactions as sole adjustable parameter, we find that a self-consistent Hartree-Fock solution reproduces extremely well the experimental behavior of the charge density wave (CDW) order parameter in the full range $0{\,<\,}T{\,<\,}T_c$, as well as the precise reciprocal space locations of the partial gap opening and Fermi arc development. The interaction strengths extracted from fitting to the experimental CDW gap are consistent with those derived from an independent Stoner-type analysis [Preview Abstract] |
Tuesday, March 14, 2017 10:36AM - 10:48AM |
E32.00010: Surface and Quantum-Confinement Effects in Ultrathin MoSi2 films Liang-Feng Huang, James Rondinelli Mo-Si-based alloys are promising structural materials for ultrahigh-temperature applications owing to their excellent mechanical strength at elevated temperature. Among the Mo-Si alloys, MoSi$_2$ exhibits outstanding oxidation resistance as a result of native SiO$_2$ scale formation. In this work, using density-functional theory calculations, we propose the alternative novel usage of MoSi$_2$ for nanoelectronics. The cleavage of MoSi$_2$ nanofilms from the layered bulk requires low energy because of the preserved chemical stoichiometry, indicating their facile synthesis in experiment. We explore the surface and quantum-confinement effects by investigating the thickness-dependent structure, stability, and electronic structure of MoSi$_2$ nanofilms, where high carrier concentrations have also been observed. The possible applications of MoSi$_2$ nanofilms as robust metallic substrates, electrodes, and in other nanodevices are discussed. In addition, we also discuss the effect of surface-induced metallicity on Raman spectra of MoSi$_2$, which are frequently used to characterize MoSi$_2$ samples. [Preview Abstract] |
Tuesday, March 14, 2017 10:48AM - 11:00AM |
E32.00011: Monolayered copper based film. Experimental observation and theoretical investigation. Pavel Sorokin, Emi Kano, Dmitry Kvashnin, Leonid Chernozatonskii, Seiji Sakai, Ayako Hashimoto, Masaki Takeguchi Here we present the report of existence of novel two-dimensional phase of copper oxide studied by experimental and theoretical methods. Using \textit{in situ} scanning transmission electron microscopy it was observed 2D CuO on graphene as well as in the graphene pore with principally different structure from the former reports Density functional theory allowed to elucidate the nature of the stability of observed CuO nanofilms. It was defined a critical role of the oxygen impurity atoms in the formation of stable 2D Cu cluster with unexpected orthogonal crystal lattice. It was found that the structure and stability of 2D Cu clusters strongly depends on the concentration and relative arrangement of oxygen impurities. Number of oxygen configurations was analyzed and the stable configuration was found corresponded well with experimental data. Additional to separated clusters, the periodic 2D CuO crystal was studied in details. Relative stability, features of elastic, electronic and magnetic properties were investigated. First-principles calculations explained the origin of the 2D phase formation and confirms the experimentally observed structures. [Preview Abstract] |
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