Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session S65: Superlattices and Nanostructures II: Transport and Electronic Phenomena |
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Sponsoring Units: DCMP Chair: Simone Assali, Ecole Polytechnique de Montreal Room: Mile High Ballroom 4F |
Thursday, March 5, 2020 11:15AM - 11:27AM |
S65.00001: Classical diffusion anomalies in two-dimensional Lorentz gases Thomas Heinzel, Beate Horn-Cosfeld, Jürgen Horbach, Nima Siboni, Rene Lohmann, Jakob Schluck The magnetoresistivity of two-dimensional Lorentz gases, formed by a free electron gas exposed to sparse, strong scatterers of identical shape at random positions, shows strong deviations from the Drude-Boltzmann model due to classical memory effects. At intermediate magnetic fields where the cyclotron radius is similar to the obstacle size, a conductance peak is observed which originates from transient superdiffusive motion along, and across, the obstacle clusters. [1] On the other hand, for strongly retroreflective [2] obstacles of sufficiently large number density, transient subdiffusive motion of the electrons is found in molecular dynamics simulations, which increases as the magnetic field approaches zero, and an anomaly ist observed for B=0 where the diffusion constant cannot be defined, similar to earlier kinetic studies at low obstacle densities.[3] A suppression of the longitudinal conductivity around zero magnetic field is measured at sub-Kelvin temperatures and interpreted as an experimental signature of this transport anomaly. |
Thursday, March 5, 2020 11:27AM - 11:39AM |
S65.00002: Kondo effect in Aharonov-Casher spin field-effect transistor Anton Parafilo, Leonid Gorelik, Mikhail Kiselev, Hee Chul Park, Robert Shekhter We address the question how Coulomb blockade in the nanowire affects the transport in Datta-Das transistor with anti-collinear partially magnetized electrodes in the regime when Kondo phenomena is reached. We use non-equilibrium Keldysh Green function technique at weak coupling regime to obtain first two non-vanishing contribution to the charge current. It is predicted that the effects of spin-orbit interaction result in a non-vanishing current for any spin polarization of the leads including the case of fully polarized anti-collinear contacts. |
Thursday, March 5, 2020 11:39AM - 11:51AM |
S65.00003: Control of Resonant Tunneling transport in III-Nitride Double-Barrier Heterostructures by δ-doping engineering Jimy Encomendero, Vladimir Protasenko, Debdeep Jena, Huili Grace Xing The spontaneous and piezoelectric polarization fields in III-Nitride semiconductors control their electronic, optical, and piezoelectric properties. Accordingly, the fundamental physics of resonant tunneling transport through nitride resonant tunneling diodes (RTDs) is also dominated by the built-in polarization fields. We have recently elucidated this connection by developing a transport model which reproduces the measured tunneling currents in multiple RTD designs. Using this model and the exponential dependence of the currents on the electric fields, we measured the polarization fields with unprecedented precision. |
Thursday, March 5, 2020 11:51AM - 12:03PM |
S65.00004: Wentzel-Kramers-Brillouin (WKB) analysis and resonant electron tunneling in α-T3 lattices Liubov Zhemchuzhna, Andrii Iurov, Godfrey Gumbs, Danhong Huang We have adopted the Wentzel-Kramers-Brillouin (WKB) theory for investigating pseudospin-1 α-T3 materials for arbitrary hopping |
Thursday, March 5, 2020 12:03PM - 12:15PM |
S65.00005: Electron tunneling and transport in α-T3 lattices under linearly polarized irradiation Paula Fekete, Andrii Iurov, Godfrey Gumbs, Danhong Huang We have considered electron tunneling through a square electrostatic potential barrier for Floquet states, i.e., pseudospin-1 Dirac electrons coupled to a dressing, off-resonant field which is linearly polarized. While for the dice lattice we can still observe an asymmetric Klein tunneling, i.e., perfect transmission for electrons colliding with the barrier that is different from the head-on case, the Klein paradox is completely suppressed for the α-T3 lattice in general with α ≠ 1. We have also calculated electron transmission for finite incidence angles and the tunneling conductance corresponding to these transmission amplitudes. |
Thursday, March 5, 2020 12:15PM - 12:27PM |
S65.00006: Incoherent Effects in Hot-Electron Quantum Optics Clarissa Barratt, Lewis Clark, Clive Emary Using dynamical quantum dot single electron pumps, high-energy (“hot”) single electrons may be injected into semiconductor systems both reliably and at a high rate. When combined with energy and time-resolved detection, electrons from these sources provide us with a new platform to probe fundamental semiconductor physics in unprecedented detail. |
Thursday, March 5, 2020 12:27PM - 12:39PM |
S65.00007: Photoconductivity of DNA-Porphyrin Complexes Daniel Van Beveren, Peco Myint, Stefanos Logothetis, Zhenqing John Qi, Carl Naylor, Mengqiang Zhao, Qicheng Zhang, Alan T Johnson, Walter Fox Smith
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Thursday, March 5, 2020 12:39PM - 12:51PM |
S65.00008: Thermal conductivity of thermally annealed nanocrystalline silicon film grown by PECVD technique Battogtokh Jugdersuren, Xiao Liu, Brian T Kearney, James Clifford Culbertson, Christopher N Chervin, Rhonda Michele Stroud Nanocrystalline silicon films (nc-Si) have been shown to have significantly lower lattice thermal conductivity than its micro-polycrystalline counterparts. However, it is essential for high temperature applications, such as thermoelectrics, to maintain their low thermal conductivity characteristics upon annealing, which may depend on the details of film preparation techniques. We investigate the effect of postdeposition thermal annealing on the thermal conductivity of nc-Si films prepared by plasma-enhanced chemical vapor deposition (PECVD) . After annealing the PECVD nc-Si at 600°C for two hours, its thermal conductivity is increased two-fold, reaching 1.86 W/mK at 300K, however this value is lower than similarly annealed nc-Si films prepared by the hot-wire chemical vapor deposition technique by a factor of 2.5. Our structural characterizations reveal that after annealing, the average crystalline grain size of PECVD nc-Si is increased to ~4.6 nm from the as-grown value of 3 nm. We discuss the possible cause of the low lattice thermal conductivity of PECVD nc-samples in terms of grain boundary scattering. |
Thursday, March 5, 2020 12:51PM - 1:03PM |
S65.00009: Strain Controlled Modulations and Anomalies in the Thermopower of Si/Ge Superlattices: A First-Principles Study Manoj Settipalli, Sanghamitra Neogi The thermopower/Seebeck coefficient (S) of metals and heavily doped semiconductors usually decreases monotonically with increasing carrier concentration, ne, following the Pisarenko relation (PR). Heterostructures, such as III-V semiconductor superlattices (SLs), have been shown to display oscillatory S, deviating from the PR. Interestingly, this behavior has not been observed in highly technologically relevant n-doped Si/Ge SLs. Here, we demonstrate a strong oscillatory behavior of the cross-plane S of n-doped Si/Ge SLs with ne, deviating from the PR, using symmetry, composition, and strain engineering. We use the density functional theory (DFT) and the effective mass approximation, independently, in combination with the Boltzmann transport equation framework, to establish the results. We predict 5.4- and 1.8-fold enhancements in the cross-plane S and the power factor of Si/Ge SLs, respectively, in the high doping regime, compared to bulk Si. In addition, our DFT study shows that cross-plane S displays anomalous sign-changing nature within the conduction miniband regime. This study will open up research directions to use strain-engineered bands to control electronic properties for various heterostructures. |
Thursday, March 5, 2020 1:03PM - 1:15PM |
S65.00010: Prediction of large Seebeck coefficient in ferroelectric domain walls of GeTe Dorde Dangic, Eamonn D Murray, Stephen B Fahy, Ivana Savic Domain walls in ferroelectric materials can have significantly different properties than their bulk counterparts, which creates new opportunities for the manipulation of material properties. GeTe is a ferroelectric material that is also an excellent thermoelectric, exhibiting relatively high electrical conductivity and Seebeck coefficient, as well as low lattice thermal conductivity. In this work, we present a first principles study indicating that ferroelectric domain walls in GeTe have a considerably larger Seebeck coefficient than bulk GeTe. Polarization discontinuity at domain walls gives rise to bound charge that localizes free charge carriers on the domain walls. We find that the two-dimensional electron gas confined to domain walls can exhibit large peaks in the local density of states near the Fermi level due to Van Hove singularities, resulting in an enhanced Seebeck coefficient. Van der Waals gaps along domain walls cause additional confinement of carriers within the domain walls that further increases the in-plane Seebeck coefficient perpendicular to the van der Waals gaps. The out-of-plane Seebeck coefficient is also significantly enhanced due to the charge localization on domain walls. |
Thursday, March 5, 2020 1:15PM - 1:27PM |
S65.00011: Visualizing Electronic Inhomogeneity in CsPbBr3 Perovskite Nanorods Yize Li, Shuang Liang, Tuong Trieu, Tyler Stabile, Zhiqun Lin Abstract: All-inorganic perovskite nanocrystals (NCs), such as CsPbBr3 NCs, have demonstrated promising applications in solar cells, light-emitting diodes (LEDs), electroluminescence devices, and lasing. Grain boundaries and point defects influence carrier transport in perovskite NCs, thereby impacting the device performance. We use contactless dielectric force microscopy (DFM), a novel scanning probe microscopy (SPM)-based imaging technique, to probe local electronic inhomogeneity in CsPbBr3 nanorods (NRs). We find that while some NRs exhibit nearly homogeneous DFM responses, others behave as p-n junctions with well-defined grain boundaries. Moreover, point defects are observed in some CsPbBr3 NRs. It is thus feasible to identify CsPbBr3 NRs that are suitable for device fabrications based on their DFM responses. |
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S65.00012: Kondo-free quantum mirage: mechanism and manipulation Qili Li, Xiaoxia Li, Bingfeng Miao, Liang Sun, Gong Chen, Ping han, Haifeng Ding Quantum mirage is a fascinating phenomenon in fundamental physics. Landmark experiment on quantum mirage reveals novel information transport at the atomic scale and exhibits great potentials for remotely probing atoms or molecules with minimized perturbation. Previous experimental investigations are Kondo effect based and quantum mirages only appear near Fermi energy. This strongly limits the exploration of the mechanism and potential application. Here we demonstrate a Kondo-free quantum mirage, which can operate in a wide energy range beyond Fermi energy. Together with an analytical model, our systematic investigations identify that quantum mirage is the result of quantum interference of the onsite electronic states with those scattered by the adatom at the focus of elliptical quantum corrals, where two kinds of scattering paths are of critical importance. Moreover, we also demonstrate the manipulation of quantum mirage with pseudo logic operations, such as NOT, FANOUT and OR gates. |
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