Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session M14: Focus Session: Mesoscopic Electronic Phenomena |
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Sponsoring Units: DMP Chair: Juan M. Merlo, Boston College Room: 008A |
Wednesday, March 4, 2015 11:15AM - 11:27AM |
M14.00001: Hydrodynamic Coulomb drag, magnetodrag and Hall drag of strongly correlated electron liquids Stanislav Apostolov, Alex Levchenko, Anton Andreev We develop a theory of Coulomb drag in ultraclean double layers with strongly correlated carriers. In the regime where the equilibration length of the electron liquid is shorter than the interlayer spacing the main contribution to the Coulomb drag arises from hydrodynamic density fluctuations. The latter consist of plasmons driven by fluctuating longitudinal stresses, and diffusive modes caused by temperature fluctuations and thermal expansion of the electron liquid. We express the drag resistivity in terms of the kinetic coefficients of the electron fluid. Our results are nonperturbative in interaction strength and do not assume Fermi-liquid behavior of the electron liquid. [Preview Abstract] |
Wednesday, March 4, 2015 11:27AM - 11:39AM |
M14.00002: Spin-charge scattering in generic Luttinger liquids Alex Levchenko We discuss the violation of spin-charge separation in generic nonlinear Luttinger liquids and investigate its effect on the relaxation, electrical and thermal transport of genuine spin-$1/2$ electron liquids in ballistic quantum wires. We identify basic scattering processes compatible with the symmetry of the problem and conservation laws that lead to the decay of plasmons into the spin modes and Brownian backscattering of spin excitations. We derive a closed set of coupled kinetic equations for the spin-charge excitations and solve the problem of conductance of interacting electrons for an arbitrary relation between the quantum wire length and spin-charge relaxation length. [Preview Abstract] |
Wednesday, March 4, 2015 11:39AM - 11:51AM |
M14.00003: Determination of time-reversal symmetry breaking lengths in an InGaAs Sagnac interferometer array Shaola Ren, J.J. Heremans, C.K. Gaspe, S. Vijeyaragunathan, T.D. Mishima, M.B. Santos Time-reversed trajectories in Aharonov-Bohm ring Sagnac interferometers yield AAS oscillations if time-reversal symmetry is preserved. The quantum interference oscillations can be used to quantify time-reversal symmetry breaking, more particularly the mesoscopic dephasing length associated with time-reversal symmetry breaking under applied magnetic field, an effective magnetic length. We measured AAS oscillations with periodicity 13 G, corresponding to h/2e flux in the 650 nm radius rings of a 5 $\times$ 5 Sagnac interferometer array fabricated on a 2D electron system in an InGaAs/InAlAs heterostructure at 0.4 K. The oscillation amplitudes were investigated over magnetic field spanning 2.2 T, with the amplitude estimated by Fourier transform over segments of 0.04 T as optimum between resolution and Fourier signal. As the magnetic field increases, the amplitude decreases due to time-reversal symmetry breaking by the magnetic flux in the interferometer arms. A dephasing model for coherent networks allows extraction of the effective magnetic length. In wide diffusive system this length corresponds theoretically and experimentally to the usual magnetic length, whereas the data show that corrections enter for ballistic quasi-1D systems (DOE DE-FG02-08ER46532, NSF DMR-0520550). [Preview Abstract] |
Wednesday, March 4, 2015 11:51AM - 12:27PM |
M14.00004: Quantum interference and correlations in single dopants and exchange-coupled dopants in silicon Invited Speaker: Joe Salfi Quantum electronics exploiting the highly coherent states of single dopants in silicon invariably requires interactions between states and interfaces, and inter-dopant coupling by exchange interactions. We have developed a low temperature STM scheme for spatially resolved single-electron transport in a device-like environment, providing the first wave-function measurements of single donors and exchange-coupled acceptors in silicon. For single donors, we directly observed valley quantum interference due to linear superpositions of the valleys [1], and found that valley degrees of freedom are highly robust to the symmetry-breaking perturbation of nearby (3 nm) surfaces. For exchange-coupled acceptors, we measured the singlet-triplet splitting, and from the spatial tunneling probability, extracted enough information about the 2-body wavefunction amplitudes to determine the entanglement entropy [2], a measure of the quantum inseparability (quantum correlations) generated by the interactions between indistinguishable particles. Entanglement entropy of the J=3/2 holes was found to increase with increasing dopant distance, as Coulomb interactions overcome tunneling, coherently localizing spin towards a Heitler-London singlet, mimicing S=1/2 particles [3]. In the future these capabilities will be exploited to peer into the inner workings of few-dopant quantum devices and shed new light on multi-dopant correlated states, engineered atom-by-atom. \\[4pt] Work done collaboratively with J. A. Mol, R. Rahman, G. Klimeck, M. Y. Simmons, L. C. L. Hollenberg, and S. Rogge.\\[4pt] [1] J. Salfi et al, (2014), Nature Mat., {\bf 13} 605.\\[0pt] [2] L. Amico et al, (2008) Rev. Mod. Phys., {\bf 80} 517-576.\\[0pt] [3] J. Salfi et al, (2014) {\textit{submitted}}. [Preview Abstract] |
Wednesday, March 4, 2015 12:27PM - 1:03PM |
M14.00005: Spin Technologies in Silicon Carbide Invited Speaker: Paul Klimov Over the past several decades SiC has evolved from being a simple abrasive to a versatile material platform for high-power electronics, optoelectronics, and nanomechanical devices. These technologies have been driven by advanced growth, doping, and processing capabilities, and the ready availability of large-area, single-crystal SiC wafers. Recent advances have also established SiC as a promising host for a novel class of technologies based on the spin of intrinsic color centers. In particular, the divacancies and related defects [1,2] have ground-state electronic-spin triplets with ms-long coherence times that can be optically addressed near telecom wavelengths [3] and manipulated with magnetic, electric [4], and strain fields [5]. Recently, divacancy addressability has been extended to the single defect level [6], laying foundation for single spin technologies in SiC. This rapidly developing field has prompted research into the SiC material host to understand how defect-bound electron spins interact with their surrounding nuclear spin bath. Although nuclear spins are typically a major source of decoherence in color-center spin systems, they are also an important resource since they interact with magnetic fields orders of magnitude more weakly than electronic spins. This fact has motivated their use for quantum memories and ultra-sensitive sensors. In this talk I will review advances in this rapidly developing field and discuss our efforts towards this latter goal. \\[4pt] [1] Koehl, et al., Nature 479, 84 (2011).\\[0pt] [2] Falk, et al., Nat. Comm. 4, 1819 (2013).\\[0pt] [3] Calusine, et al., APL 105, 011123 (2014).\\[0pt] [4] Klimov, et al., PRL 112, 087601 (2014).\\[0pt] [5] Falk, et al., PRL 112, 187601 (2014).\\[0pt] [6] Christle, et al., Nat. Mat. accepted (2014). [Preview Abstract] |
Wednesday, March 4, 2015 1:03PM - 1:15PM |
M14.00006: Al Nanowire Arrays For Plasmonic Devices Nathan T. Nesbitt, Aaron H. Rose, Yitzi M. Calm, Juan M. Merlo, Steve Shepard, Greg McMahon, Chia-Kuang Tsung, Michael J. Burns, Michael J. Naughton Aluminum nanowires have been fabricated in ordered vertical arrays on bulk Al foil with controlled wire dimensions and spacing. Large aspect ratio wires were obtained, including sub-micron wire diameters and supra-10 $\mu m$ height. The somewhat novel method of fabrication utilizes nanoimprint lithography and the economical electrochemical anodization process used to make anodized aluminum oxide (AAO) templates, suggesting potential facile production and scalability. To our knowledge, arrays of vertical metallic nanowires (i.e. differing from semiconductor nanowire or carbon nanofiber arrays) of the obtained dimensions have not previously been reported. These dimensions may be favorable for nanoscale photonic and plasmonic transmission, nanocoax solar cells, and non-diffaction-limited optical microscopy. [Preview Abstract] |
Wednesday, March 4, 2015 1:15PM - 1:27PM |
M14.00007: ABSTRACT WITHDRAWN |
Wednesday, March 4, 2015 1:27PM - 1:39PM |
M14.00008: Dielectric tuned surface plasmon resonances on metallic gratings Adam Hauser, Bill Flaherty, Ka Ming Law, Evgeny Mikheev, Adam Kajdos, Susanne Stemmer, S. James Allen We explore the effect of substrate dielectric constant on the dispersion of infrared surface plasmons supported by micron scale metal gratings. Of particular interest are substrate dielectrics that can be tuned by electric fields and thereby make possible gated plasmonic devices. Angle resolved s and p polarized reflectivity is used to observe the plasmon dispersion for Pt gratings on various oxide dielectrics and heterostructures, LSAT, SrTiO$_{3}$, Nb:SrTiO3 and LSAT/SrTiO$_{3}$/GdTiO$_{3}$. Most striking is the shift in the plasmon dispersion upon Nb doping of SrTiO$_{3}$ caused by the free carrier contribution to the dielectric constant. We focus our attention on a metal-oxide-metal heterostructure, Pt/Ba$_{\mathrm{x}}$Sr$_{\mathrm{1-x}}$TiO$_{3}$/Pt-grating that serves to confine the infrared field to the electric field modulated region enhancing the potential for a gated plasmonic structure. [Preview Abstract] |
Wednesday, March 4, 2015 1:39PM - 1:51PM |
M14.00009: Surface plasmons as a tool to modify the magnetic properties of nanomagnets Fernando Galvez, Miguel Angel Garcia, David Perez de Lara, Jose L. Vicent We have fabricated on Si substrates arrays of permalloy/gold nanostructures by electron beam lithography and sputtering techniques. These nanostructures allow studying the interplay between surface plasmons and magnetism. Direct coupling between magneto-optical activity and excitation of surface plasmon resonance is a topic which has called the attention of many researchers. In this work we follow a different approach; we explore the possibility to modify the magnetic properties of the Py nanomagnets, i. e., hysteresis loops by local excitation of surface plasmons via an increase of temperature. We present preliminary results using an experimental setup which allows measuring at the same time surface plasmon resonance and magnetization curves. [Preview Abstract] |
Wednesday, March 4, 2015 1:51PM - 2:03PM |
M14.00010: Small Footprint Nano-Mechanical Plasmonic Phase Modulators Brian Dennis, Michael Haftel, David Czaplewski, Daniel Lopez, Girsh Blumberg, Vladimir Aksyuk Miniaturization of photonic devices is fundamentally limited by the refractive index of the constituent dielectric materials. By coupling light to metal's free electrons, plasmonic devices achieve deeper localization, which scales down with the device geometric size. However, when the localization approaches the skin depth, energy shifts from the dielectric into the metal, and modulation via the electro-optic effect in the dielectric becomes less efficient. Here we propose a nano-electromechanical phase modulation principle exploiting the extraordinarily strong dependence of the phase velocity of metal-insulator-metal (MIM) gap plasmons on dynamically variable gap size. We demonstrate a 23 $\mu $m long non-resonant modulator having a 1.5 $\pi $ rad range with 1.7 dB excess loss at 780 nm. Analysis shows that an ultracompact 1 $\mu $m$^{2}$ footprint $\pi $ rad phase modulator can be realized, more than an order of magnitude smaller than any previously shown. This size reduction can be realized without incurring extra loss, since the nanobeam-plasmon coupling strength increases at a similar rate as the loss. Such small, high density electrically controllable components may find applications in optical switch fabrics and reconfigurable flat plasmonic optics. [Preview Abstract] |
Wednesday, March 4, 2015 2:03PM - 2:15PM |
M14.00011: Interferometric Plasmonic Lensing with Nanohole Arrays Yu Gong, Alan Joly, Patrick El-Khoury, Wayne Hess Nonlinear photoemission electron microscopy (PEEM) is used to map propagating surface plasmons launched from lithographically patterned isolated nanoholes and nanohole arrays in gold films. A damped elongated ring-like photoemission beat pattern is observed from individual nanoholes. Strong near field photoemission patterns are observed in the PEEM images, recorded following low angle of incidence irradiation of the plasmonic nanohole arrays with sub-15 fs laser pulses centered at 780 nm. The recorded photoemission patterns are attributed to constructive and destructive interference between propagating surface plasmons launched from the individual nanoholes which comprise the array. By exploiting the wave nature of propagating surface plasmons, we demonstrate how varying the array geometry (hole diameter, pitch, and number of rows/columns) ultimately yields intense localized photoemission patterns. Through a combination of PEEM experiments and finite-difference time-domain simulations, we identify the optimal array geometry for efficient light coupling and interferometric plasmonic lensing. We also describe an exemplary practical application of the nanohole array-based plasmonic lenses, namely, enhanced photoemission from a vertex of a strategically positioned gold triangle. [Preview Abstract] |
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