Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session L27: Semiconductors and the Hall Effect III. |
Hide Abstracts |
Sponsoring Units: FIAP Chair: J Heremans, Virginia Tech Room: 290 |
Wednesday, March 15, 2017 11:15AM - 11:27AM |
L27.00001: Theory of semiconductor nanoplatelet growth: How an intrinsic growth instability leads to highly anisotropic, quasi-two-dimensional platelets Steve Erwin, Andreas Riedinger, Florian Ott, Aniket Mule, Sergio Mazzotti, Philippe Knuesel, Stephan Kress, Ferry Prins, David Norris Colloidal nanoplatelets are atomically flat, quasi-two-dimensional sheets of semiconductor that can exhibit efficient, spectrally pure fluorescence. Despite intense interest in their properties, the mechanism behind their highly anisotropic shape and precise atomic-scale thickness remains unclear, and even counterintuitive for commonly studied nanoplatelets that arise from isotropic crystal structures (e.g. zincblende CdSe and lead-halide perovskites). We show theoretically that an intrinsic instability in growth kinetics leads to such highly anisotropic shapes. By combining experimental results on the synthesis of CdSe nanoplatelets with theory predicting enhanced growth on narrow surface facets, we develop a model that explains nanoplatelet formation as well as observed dependencies on time and temperature. Based on standard concepts of volume, surface, and edge energies, the resulting growth instability criterion can be directly applied to other crystalline materials. [Preview Abstract] |
Wednesday, March 15, 2017 11:27AM - 11:39AM |
L27.00002: Aharonov-Bohm oscillations due to ballistic closed trajectories in elliptic self-focusing geometries Yuantao Xie, J. J. Heremans, S. Vijeyaragunathan, T. D. Mishima, M. B. Santos An array of elliptic stadia is defined on an InGaAs quantum well with electron mean free path \textasciitilde 3 micron at 0.38 K, such that ballistic phase coherent transport prevails. In the structure, classical trajectories starting at one focus will after reflection from the elliptic potential wall pass through the other focus, and then back to the starting focus, generating classical closed orbits with lengths comparable to the mean free path, assuming just two elastic specular scattering events. In perpendicular magnetic fields the magnetoresistance at 0.38 K and 1.2 K shows Aharonov-Bohm oscillations due to quantum interference over the closed trajectories, with h/e periodicity corresponding to the area enclosed by the trajectories. Fourier spectra of the magnetoresistance reveal two peaks, consistent with numeric simulations showing two stable classical trajectories under a wide range of magnetic fields. Ballistic Altshuler-Aronov-Spivak oscillations due to time-reversed trajectories appear absent in the array, likely suppressed by time reversal symmetry breaking due to the local magnetic field at the electron paths at higher fields, and masked by antilocalization from other closed orbits at lower fields (DOE DE-FG02-08ER46532 and NSF DMR-1207537). [Preview Abstract] |
Wednesday, March 15, 2017 11:39AM - 11:51AM |
L27.00003: Evolution of phonon and electronic structures of transition metal dichalcogenides as a function of large uniaxial strain Ali Dadgar, Abhay Pasupathy, Elton Santos, Marcos Pimenta, E.H. Yang, Kyung Nam Kang, Declan Scullion, Peter Rice, Irving Herman Monolayer transition metal dichalcogenides (TMD), like graphene, are highly stretchable materials. The application of uniaxial strain to semiconductor materials changes band gaps, effective masses and scattering mechanisms. Here, we present techniques by which large (several percent) controllable strain can be applied to the semiconducting TMD materials by using polymer encapsulation. Our versatile method allows for the application of both compressive and tensile strain. Using polarized Raman spectroscopy, we monitor the changes to the lattice structure and compare results to those expected from ab-initio theoretical calculations. Using photoluminescence measurements, we track the changes in the excitonic transitions in these materials and show that the optical response of two-dimensional semiconductors is highly tunable using uniaxial strain. [Preview Abstract] |
Wednesday, March 15, 2017 11:51AM - 12:03PM |
L27.00004: Tunability and Stability of Lead Sulfide Quantum Dots in Ferritin J. Ryan Peterson, Kameron Hansen Quantum dot solar cells have become one of the fastest growing solar cell technologies to date, and lead sulfide has proven to be an efficient absorber. However, one of the primary concerns in dye-sensitized quantum dot solar cell development is core degradation. We have synthesized lead sulfide quantum dots inside of the spherical protein ferritin in order to protect them from photocorrosion. We have studied the band gaps of these quantum dots and found them to be widely tunable inside ferritin just as they are outside the protein shell. In addition, we have examined their stability by measuring changes in photoluminescence as they are exposed to light over minutes and hours and found that the ferritin-enclosed PbS quantum dots have significantly better resistance to photocorrosion. [Preview Abstract] |
Wednesday, March 15, 2017 12:03PM - 12:15PM |
L27.00005: Dynamical birefringence: Electron-hole recollisions as a probe of Berry curvature Qile Wu, Hunter Banks, Darren Valovcin, Shawn Mack, Arthur Gossard, Loren Pfeiffer, Renbao Liu, Mark Sherwin Electron-hole recollisions and high-order sideband generation (HSG) occur when a near-band gap laser beam excites a semiconductor that is driven by sufficiently strong, THz-frequency electric fields. We report theoretical studies of HSG in GaAs/AlGaAs quantum wells based on recent experimental observations: (1) Sidebands with order greater than 20 are usually stronger when the near-infrared (NIR) electric field is polarized perpendicular to the THz electric field than when they are parallel. (2)Even though the polarization of the exciting NIR laser is nearly linear, the sidebands exhibit significant ellipticity. We call these phenomena dynamical birefringence. With non-Abelian Berry curvature as an essential part, a generalization of the three-step model for high-order harmonic generation is proposed to explain these phenomena. Dynamical birefringence arises from quantum interference between electron-hole recollision pathways associated with electron-hole pairs that were injected with opposite spins. We also carry out quantum simulations to confirm the Berry physics. Our results open the door to direct measurements of the complete electronic structure of semiconductors and insulators near the $\Gamma$ point, including band structure, scattering rates, and Berry curvature. [Preview Abstract] |
Wednesday, March 15, 2017 12:15PM - 12:27PM |
L27.00006: Parafermion supporting platform based on ferromagnetic transitions in the fractional quantum Hall effect regime Tailung Wu, Aleksandr Kazakov, Kenneth West, Loren Pfeiffer, Leonid Rokhinson, Zhong Wan Promise of fault tolerant quantum computing sparked research in Majorana excitations, yet their rotational symmetry group is not dense enough to allow universal qubit operations. Formation of higher order non-Abelian excitations requires even more complex system compared to the challenging task to support Majorana fermions: addition of strong interactions that fractionalize charge excitations. We propose a new platform based on ferromagnetic transitions in the fractional quantum Hall effect regime, where superconductivity induced in helical domain walls should support parafermion excitations. In this work we will present results on gate control of ferromagnetic transitions at filling factor $\nu=2/3$ and deterministic formation of domain walls (DWs) in multi-gate devices. Transport characteristics of domain walls and their length dependence will be discussed. Reconfigurable network of such DWs, couple to superconducting contacts, can be used to demonstrate non-Abelian statistics of parafermionic excitations and realize topological qubits. [Preview Abstract] |
Wednesday, March 15, 2017 12:27PM - 12:39PM |
L27.00007: A Comparative Study of Cyclotron Decay in Two-dimensional Electron Gas Samples. B. Barman, A.L. OBeirne, A.G. Linn, J.A. Curtis, J. Holleman, C. Garcia, T. Tokumoto, J.L. Reno, S.A. McGill, D. Karaiskaj, D.J. Hilton We used THz time-domain spectroscopy to study cyclotron decay times in high mobility GaAs 2DEGs of varying well widths (30nm and 12 nm). All the measurements were done at a magnetic field of 0.8T as a function of temperature (0.4-10 K). We compare the characteristic cyclotron decay times in both types of samples, as a function of temperature, to examine the influence of surface scattering and strong quantum confinement. Our previous work has shown that the cyclotron decay time exceeds the single particle/quantum lifetime by \textasciitilde 60x in the 30nm 2 DEG QW[1], which we attribute to the influence of small angle scattering in the high-mobility limit $\mu $\textunderscore DC$=$3.6$\times$ 10\textasciicircum 6 cm\textasciicircum 2 V\textasciicircum (-1) s\textasciicircum (-1). [1]Jeremy A. Curtis et al., Physical Review B 93 (15), 155437 (2016). [Preview Abstract] |
Wednesday, March 15, 2017 12:39PM - 12:51PM |
L27.00008: THz Time-Domain Magneto-spectroscopy of GaAs 2DEG in the 25 T Split-Florida Helix Ashlyn D. Burch, J.A. Curtis, A.G. Linn, B. Barman, M.J. Stiles, J.L. Reno, S.A. McGill, D. Karaiskaj, D.J. Hilton We have developed a gas plasma based THz time--domain spectrometer (TTDS) coupled with an air-breakdown coherent detection (ABCD) system, to study Landau quantized 2 DEG samples, in the 25 T Split-Florida Helix magnet at the National High Magnetic Field Laboratory (NHMFL). Through the use of non-linear optics, we achieved a larger bandwidth (approx. 0.1-10 THz) compared to traditional fiber-based experimental techniques. We used this system to perform the first high magnetic field TTDS measurements on a high mobility GaAs 2DEG sample. 1. Zhang, et al., Superradiant Decay of Cyclotron Resonance of Two-Dimensional Electron Gases. Physical Review Letters 113, 047601 (2014). 2. T. Arikawa, et al, Terahertz Coherent Control of a Landau-Quantized Two-dimensional Electron Gas, Physical Review B 84, 241307 (2011). [Preview Abstract] |
Wednesday, March 15, 2017 12:51PM - 1:03PM |
L27.00009: Formation Mechanism of Self Assembled Horizontal ErSb Nanowires Embedded in a GaSb(001) Matrix Nathaniel Wilson, Stephan Kraemer, Chris Palmstrøm The Er$_{x}$Ga$_{1-x}$Sb exhibits a variety of self-assembling nanostructures. In order to harness these nanostructures for use in devices and other material systems it is important to understand their formation. We have characterized the growth mechanism of self-assembled horizontal ErSb nanowires in a GaSb(001) matrix through the use of in-situ Scanning Tunneling Microscopy (STM) as well as ex-situ Transmission Electron Microscopy (TEM). We observe large GaSb macrosteps on the growth surface of Er$_{.3}$Ga$_{.7}$Sb samples. The areas near the ledge and base of the macrosteps show significant differences in size and distribution of ErSb nanowires. Results suggest that the formation of macrosteps drives the transition from vertical to horizontal nanowires in the Er$_{x}$Ga$_{1-x}$Sb system. We also observe a low temperature growth mode, which results in horizontal nanowire formation under a wide range of flux conditions. This new growth mode does not exhibit the embedded growth observed in the formation of nanowires at higher temperatures and may allow for horizontal nanowire formation without the presence of macrosteps, as well as the formation of smaller nanoparticles which may be useful for achieving smaller nanoparticle dimensions and electron confinement effects. [Preview Abstract] |
Wednesday, March 15, 2017 1:03PM - 1:15PM |
L27.00010: Three-Dimensional Lattice Matching of Epitaxially Embedded Nanoparticles Brelon May, Peter Anderson, Roberto Myers Since Mathews and Blakeslee developed a theory of atomic lattice matched thin films in 1974, epitaxy has been modeled using 2D lattice-matching considering only the in-plane strain $\left( {\varepsilon_{IP}^{\ast } } \right)$. Here, we present a 3D model to predict the conditions at which epitaxially encased nanoparticles relax by plastic deformation, including the out-of-plane lattice mismatch $\left( {\varepsilon_{OP}^{\ast } } \right)$. The critical particle length $\left( {L_{C} } \right)$ at which defect formation proceeds is determined by balancing the resulting reduction in strain energy from a dislocation, with the corresponding increase in the energy of formation. Our results use a modified Eshelby inclusion technique for an embedded nanoparticle, shedding new light on the epitaxy of nanostructures. By tailoring $\varepsilon_{IP}^{\ast } $ and $\varepsilon _{OP}^{\ast } $, $L_{C} $ can be increased to 70{\%} beyond the case of encapsulation in a homogenous matrix. An InAs nanoparticle embedded in GaN $\left( {\varepsilon_{IP}^{\ast } =\varepsilon_{OP}^{\ast } =-0.072} \right)$ results in $L_{C} =10.8$ nm. However, it can be increased to $16.4$ nm when grown on GaAs and surrounded by InSb $\left( {\varepsilon _{IP}^{\ast } =-0.072,\varepsilon_{OP}^{\ast } =+0.065} \right)$, and a maximum of $18.4$ nm if the particle is capped by an alloy with $\varepsilon _{OP}^{\ast } =+0.037$. This effect, which we term ``3D Poisson-stabilization'', provides a means to increase the strain tolerance and modify the strain state in epitaxial heterostructures through the engineering of $\varepsilon_{OP}^{\ast } $. [Preview Abstract] |
Wednesday, March 15, 2017 1:15PM - 1:27PM |
L27.00011: Bandgap engineering and structure analysis of ZnO/ Al$_{\mathrm{2}}$O$_{\mathrm{3}}$ superlattices grown by atomic layer deposition. W.C. Hsieh, Q.Y. Chen, P.V. Wadekar, C.F. Chang, H.C. Huang, C.M. Shiau, Y.P. Cheng, Y.S. Hong, C.Y. Dang, P.C. Kung, C.H. Lee, S.H. Huang, Z.Y. Wu, Y.Y. Liang, C.M. Lin, S.T. You, L.W. Tu, N.J. Ho, H.W. Seo, W.K. Chu ALD-grown ZnO/Al$_{\mathrm{2}}$O$_{\mathrm{3}}$ superlattices (SLS) as analyzed by XRR assisted with GenX fittings exhibit a consistent mass density for the ZnO layers of 5.6 g/cm$^{\mathrm{3}}$, largely that of the bulk crystal. However, for Al$_{\mathrm{2}}$O$_{\mathrm{3}}$, the value is \textasciitilde 2.95 g/cm$^{\mathrm{3}}$ versus the ideal 3.95 g/cm$^{\mathrm{3}}$. This discrepancy suggests a highly porous Al$_{\mathrm{2}}$O$_{\mathrm{3}}$, possibly due to the presence of hydrogen in an AlO(OH) amorphous boehmite phase. TEM imaging portrays the periodic structures consistent with the XRR findings. The ZnO layers are c-textured while Al$_{\mathrm{2}}$O$_{\mathrm{3}}$ amorphous. Room-temperature CL measurements showed decreasing ZnO bandgap as the Al$_{\mathrm{2}}$O$_{\mathrm{3}}$ cycles increased, hinting at feasible bandgap engineering through SLS structural variations. Amorphous Al$_{\mathrm{2}}$O$_{\mathrm{3}}$ is known to have a smaller bandgap of 5.7-7.1 eV as compared to 7.1-8.8 eV for bulk crystals. CL also showed a peak at \textasciitilde 5.1 eV, thus consistent with our conjecture of the am-Al$_{\mathrm{2}}$O$_{\mathrm{3}}$. [Preview Abstract] |
Wednesday, March 15, 2017 1:27PM - 1:39PM |
L27.00012: Imaging the Incipient Wigner electron lattice in a quantum wire Sheng-Chin Ho, Heng-Jian Chang, Chia-Hua Chang, Graham Creeth, Sanheev Kumar, Michael Pepper, Jonathan Griffiths, Ian Farrer, Geraint Jones, David Ritchie, Tse-Ming Chen One-dimensional system abounds with physics especially considering electron-electron interaction. Electrons have been theoretically predicted to form a zigzag Wigner crystal when the electron density in a quantum wire approaches to specific magnitude. SO far such Wigner crystallization can only be inferred from conductance plateaus [1,2] and spatially resolved imaging of it remains a challenge. Here we utilize magnetic focusing technique[3] to probe the formation of a Wigner lattice, in which the spatial distribution of electrons in a quantum wire reveals itself in the magnetic focusing spectrum. Evolution from a focusing peak singlet to doublet --- in response to a one -dimensional single row transport to Wigner crystallization--- is shown when the density is continuously varied. Additionally, the focusing peak doublet is found to develop into a singlet with increasing temperature. [1] W. K. Hew \textit{et al.} Phys. Rev. Lett. 102, 056804 (2009). [2] L. W. Smith\textit{ et al. Phys. Rev. B} 80, 041306 (2009). [3] H. van Houten et al., Phys. Rev. B 39, 8556(1989). [Preview Abstract] |
Wednesday, March 15, 2017 1:39PM - 1:51PM |
L27.00013: Finding a place to die: the fate of a Landau quasi-particle in quantum Hall edge channels Cl\'ement Cabart, Benjamin Roussel, Pascal Degiovanni, Dario Ferraro, Arthur Marguerite, Gwendal F\`eve Following the recent demonstration of single-electron sources [Science {\bf 316}, 1169 (2007)], a new focus has appeared in low-dimensional condensed-matter systems towards the manipulation of coherent electronic excitations. One particular study of importance concerns the fate of energy-resolved single-electronic excitations under the effect of Coulomb interactions. This problem, which was the start of the Landau-Fermi liquid theory for systems of dimension two or more, has still to be tested experimentally at the single-particle level. In this talk, we present both recent theoretical predictions [Phys. Rev. Lett. {\bf 113}, 166403 (2014)] for this problem and new experimental results [Phys. Rev. B {\bf 94}, 115311 (2016)]. Using an electronic Wigner function, we visualize the role of many-body decoherence in the evolution of a single electron, which allows us to compare theoretical results with experimental data obtained through Hong-Ou-Mandel interferometry. This shows a clear agreement between theory and experiments, providing a full quantitative study of the Landau quasi-particle relaxation problem in one-dimensional conductors. In particular, we show that interactions restore indistinguishability for two electrons initially emitted in almost orthogonal wavepackets. [Preview Abstract] |
Wednesday, March 15, 2017 1:51PM - 2:03PM |
L27.00014: Dynamic electron transport in an oxide heterostructure Hangtian Hou, Chris Ford, Ateeq Nasir, Rhodri Mansell, Jung-Wei Liao, Jonathan Griffiths, Yusuke Kozuka, Masashi Kawasaki From spontaneous and piezoelectric polarization, a correlated two-dimensional free electron gas forms at a ZnO/MgZnO heterointerface with a low density of 10$^{11}$cm$^{-2}$ and a high mobility of 10$^{6}$ cm$^{2}$V$^{-1}$s$^{-1}$. Both integral and frictional quantum hall effect were observed at this system due to the strong electron-electron correlation. In fabrication we succeed to pattern nano surface metallic gates by electron-beam lithography to provide further confinements to form quasi-1D quantum wires or quantum dots. A conductance oscillation through the 1D channel was observed at a low temperature, which explained by ballistic quasi-1D electron transport and Coulomb blockage. Different to a traditional GaAs system, ZnO has the weak spin-orbit interaction and long electron coherence time, which make it ideal for spintronic applications. Moreover, ZnO is a good piezoelectric substrate for surface acoustic waves quantum device (SAWs), which has showed strong ability in single electron transport. We applied the dynamic SAW quantum dot technique on this ZnO-based 2DEG system, wishing to realize a more efficient single electron charge and spin transfer than other semiconductor heterostructures. [Preview Abstract] |
Wednesday, March 15, 2017 2:03PM - 2:15PM |
L27.00015: Quantum Generation Dynamics of Coherent Phonon in Semiconductors: Analysis of Pulse Laser Dependence Yohei Watanabe, Ken-ichi Hino, Muneaki Hase, Nobuya Maeshima Coherent phonon (CP) generation is induced by an ultrafast pulse laser and investigated in various materials. The mechanism of CP generation has been described by two phenomenological models referred to as the impulsive stimulated Raman scattering and the displacive excitation of CP, respectively, where the initial phase of the CP oscillation is considered to be a key parameter. However the models are little in harmony with the existing experimental results and the initial phase is still one of the controversial problems on CP generation. In the present study, we show the dependence of the initial phases on pulse-laser conditions such as pulse width and Rabi frequency for both of polar and non-polar semiconductors. The initial phases are extracted by ab initio solving quantum dynamic equations concerned with the electron-light interaction and the electron-phonon interaction [1]. The resulting initial phases are attributed to the electron-light interaction and the phase factor of the electron-phonon interaction. [1] Y. Watanabe, K. Hino, M. Hase and N. Maeshima, Phys. Rev. B (submitted), arXiv:1510.00263. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700