Bulletin of the American Physical Society
2018 Annual Meeting of the APS Four Corners Section
Volume 63, Number 16
Friday–Saturday, October 12–13, 2018; University of Utah, Salt Lake City, Utah
Session L01: CMP + Materials 7: Superconductors |
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Chair: Y.-S. Wu, University of Utah Room: JFB 101 |
Saturday, October 13, 2018 11:20AM - 11:56AM |
L01.00001: Thermoelectric Effects in Superconductor-Ferromagnet Hybrids Invited Speaker: Meenakshi Singh Superconductor-ferromagnet (S/F) hybrids host a profusion of fascinating phenomena rooted in the conflicting spin orders of the two component systems. Most experimental studies of these systems have focused on charge and spin transport measurements. Thermal properties remain largely experimentally unexplored. This is not for lack of exciting predictions, including a dramatic increase in the thermoelectric figure of merit of S/F hybrids compared to either system alone. This talk will focus on experimental design and measurements to determine the thermoelectric figure of merit in S/F hybrids. The effects that the dimensionality, type of superconductivity, and Andreev reflections have on thermal phenomena, and potential applications like thermoelectric cooling at sub-Kelvin temperatures will also be discussed. |
Saturday, October 13, 2018 11:56AM - 12:08PM |
L01.00002: Thermoelectric properties of Copper Benzenehexathiol Ryuichi Tsuchikawa, Neda Lotfizadeh, Nabajit Lahiri, Shuwan Liu, Mackenzie Lach, Celine Slam, Janis Louie, Vikram V Deshpande Copper benzenehexathiol (CuBHT) is an electrically conductive, two-dimensional (2D) metal-organic framework (MOF). It has a potential to be a new class of organic thermoelectric material because of its high electrical conductivity and low thermal conductivity arising from periodic nano-sized pores [1,2]. We measured the thermal conductivity, electrical conductivity, and Seebeck coefficient of thin flakes of Cu-BHT in a mesoscopic device scale. Our measurement of thermal conductivity shows that the phonon mean free path is determined by pore separations even at room temperature, and the temperature dependence of electrical conductivity shows a wide range of variations due to the highly anisotropic connectivity of the 2D CuBHT domains, giving an independent tunability of σ. The thermoelectric figure of merit, ZT, a measure of the efficiency of the energy conversion from heat to electricity, is found to be relatively small as compared with Bi2Te3 but is still one of the highest values for MOFs [2].
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Saturday, October 13, 2018 12:08PM - 12:20PM |
L01.00003: Calculating the Superconducting Superheating Field and Critical Wavelength Using Automatic Differentiation within Ginzburg-Landau Theory Mark Transtrum, Alden Pack For many physical systems the stability and equations of motion are derived by calculating variations of a free energy. We show how automatic differentiation simplifies the task of evaluating these variations while avoiding tedious calculations performed by hand or through symbolic computation. We illustrate its usefulness by recalculating the superconducting superheating field and critical wavelength of type-II superconductors within Ginzburg-Landau theory. |
Saturday, October 13, 2018 12:20PM - 12:32PM |
L01.00004: Modeling of 2DEG Formation at Polar ε-(AlGa)2O3/ε-Ga2O3 Heterojunctions Praneeth Ranga, Sung Beom Cho, Rohan Mishra, Sriram Krishnamoorthy We report on the modeling of two-dimensional electron gas (2DEG) formation at the ε-AlGaO3/ε-Ga2O3 interface. Orthorhombic ε-Ga2O3 is the second most stable polymorph of Ga2O3, with an ultra-wideband gap. ε-Ga2O3 is predicted to be a ferroelectric material (APPLIED PHYSICS LETTERS 112, 162101 (2018)), with much larger polarization than polar Gallium Nitride. A (2DEG) formed between polar materials is expected to exhibit high charge density and higher mobility compared to a modulation-doped heterostructure due to the absence of impurity and remote scattering. Ab-initio density functional theory (DFT) modeling was performed on ordered and disordered alloys of ε-(AlGa)2O3 to calculate spontaneous polarization, piezoelectric and stiffness coefficients. Band Diagrams calculations using Schrödinger-Poisson simulations show the formation of 2DEG at ε-AlGa2O3/ ε-Ga2O3 interface with a large sheet charge in the range of 1e13- 5e13 cm-2 . This work is the first investigation of polar ε-Ga2O3 based heterostructures for potential high frequency and high-power applications. |
Saturday, October 13, 2018 12:32PM - 12:44PM |
L01.00005: Electric and Magnetic Properties of Tungsten Doping in VO2/Ni multilayers Logan Sutton, Joshua P Lauzier, Jose De La Venta The effect of W doping in VO2 on the structural, electrical, and magnetic properties of VO2/Ni heterostructures through the VO2 phase transition was studied. It is well-known that VO2 has a Structural Phase Transition (SPT) coincident with a metal-insulator transition (MIT) around 340 K, from a low temperature insulating monoclinic (M) to a high temperature metallic rutile (R) structure [1]. Doping VO2 with W is known to lower the transition temperature proportional to the doping percentage [2]. The SPT of VO2 induces an inverse magnetoelastic effect that strongly modifies the coercivity and magnetization of the Ni films [3]. Doped films were grown using two techniques; reactive magnetron co-sputtering of V and W in an O2 environment, and spin coating using a sol-gel process. Doped films showed both a shift in temperature and suppression of the MIT proportional to doping percentage consistent with previous studies. A sharp decrease in the coercivity at the shifted SPT is observed for all samples grown using the sol-gel technique. Doped samples grown using magnetron sputtering have not shown any magnetoelastic effect. 1. N.F. Mott, Rev. Mod. Phys. 40, 677 (1968). 2. Shibuya K. et al, Appl. Phys. Lett. 96 (2010). 3. J. De La Venta et al, Appl. Phys. Lett. 104 (2014). |
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