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Articles 1  14 of 14
FullText Articles in Physics
SpinPhotovoltaic Effect In Quantum Wires Due To Intersubband Transitions, Arkady Fedorov, Yuriy V. Pershin Dr, Carlo Piermarocchi
SpinPhotovoltaic Effect In Quantum Wires Due To Intersubband Transitions, Arkady Fedorov, Yuriy V. Pershin Dr, Carlo Piermarocchi
Faculty Publications
We consider the current induced in a quantum wire by external electromagnetic radiation. The photocurrent is caused by the interplay of spinorbit interaction (Rashba and Dresselhaus terms) and an external inplane magnetic field. We calculate this current using a Wigner functions approach, taking into account radiationinduced transitions between transverse subbands. The magnitude and the direction of the current depends on the Dresselhaus and Rashba constants, strength of magnetic field, radiation frequency, and intensity. The current can be controlled by changing some of these parameters.
LaserControlled Local Magnetic Field With Semiconductor Quantum Rings, Yuriy V. Pershin Dr, Carlo Piermarocchi
LaserControlled Local Magnetic Field With Semiconductor Quantum Rings, Yuriy V. Pershin Dr, Carlo Piermarocchi
Faculty Publications
We analyze theoretically the dynamics of N electrons localized in a narrow semiconductor quantum ring under a train of phaselocked infrared laser pulses. The pulse sequence is designed to control the total angular momentum of the electrons. The quantum ring can be put in states characterized by strong currents. The local magnetic field created by these currents can be used for a selective quantum control of single spins in semiconductor systems. The current generation in quantum rings with finite width is also studied.
Photovoltaic Effect In Bent Quantum Wires In The Ballistic Transport Regime, Yuriy V. Pershin Dr, Carlo Piermarocchi
Photovoltaic Effect In Bent Quantum Wires In The Ballistic Transport Regime, Yuriy V. Pershin Dr, Carlo Piermarocchi
Faculty Publications
A scheme for the generation of a photocurrent in bent quantum wires is proposed. We calculate the current using a generalized LandauerBüttiker approach that takes into account the electromagnetic radiation. For circularly polarized light, it is demonstrated that the curvature in the bent wire induces an asymmetry in the scattering coefficients for left and right moving electrons. This asymmetry results in a current at zero bias voltage. The effect is due to the geometry of the wire which transforms the photon angular momentum into translational motion for the electrons. Possible experimental realizations of this scheme are discussed.
Terahertz Studies Of The Dielectric Response And SecondOrder Phonons In A Gase Crystal, B. L. Yu, F. Zeng, V. Kartazayev, R. R. Alfano, K. C. Mandal
Terahertz Studies Of The Dielectric Response And SecondOrder Phonons In A Gase Crystal, B. L. Yu, F. Zeng, V. Kartazayev, R. R. Alfano, K. C. Mandal
Faculty Publications
No abstract provided.
Semiconductor Nanowire Laser And Nanowire Waveguide ElectroOptic Modulators, Andrew B. Greytak, Carl J. Barrelet, Yat Li, Charles M. Lieber
Semiconductor Nanowire Laser And Nanowire Waveguide ElectroOptic Modulators, Andrew B. Greytak, Carl J. Barrelet, Yat Li, Charles M. Lieber
Faculty Publications
Electric field modulation of visible and ultraviolet nanoscale lasers consisting of single CdS or GaN nanowires has been achieved using integrated, microfabricated electrodes. Modulation of laser emission intensity is achieved with no detectable change in the laser wavelength. The devices can also be operated below the lasing threshold to modulate the intensity of light propagating within the nanowire waveguide. Studies of the electric field dependence in devices of varied geometry indicate that modulation is due to an electroabsorption mechanism. These findings expand opportunities for multicolor, nanowirebased photonic devices and circuits.
Persistent And RadiationInduced Currents In Distorted Quantum Rings, Yuriy V. Pershin Dr, Carlo Piermarocchi
Persistent And RadiationInduced Currents In Distorted Quantum Rings, Yuriy V. Pershin Dr, Carlo Piermarocchi
Faculty Publications
Persistent and radiationinduced currents in distorted narrow quantum rings are theoretically investigated. We show that ring distorsions can be described using a geometrical potential term. We analyze the effect of this term on the current induced by a magnetic flux (persistent current) and by a polarized coherent electromagnetic field (radiationinduced current). The strongest effects in persistent currents are observed for distorted rings with a small number of electrons. The distortion smoothes the current oscillations as a function of the magnetic flux and changes the temperature dependence of the current amplitude. For radiationinduced currents, the distortion induces an ac component in ...
Spin Photovoltaic Effect In Quantum Wires With Rashba Interaction, Yuriy V. Pershin Dr, Carlo Piermarocchi
Spin Photovoltaic Effect In Quantum Wires With Rashba Interaction, Yuriy V. Pershin Dr, Carlo Piermarocchi
Faculty Publications
We propose a mechanism for spinpolarized photocurrent generation in quantum wires. The effect is due to the combined effect of Rashba spinorbit interaction, external magnetic field, and microwave radiation. The timeindependent interactions in the wire give rise to a spectrum asymmetry in k space. The microwave radiation induces transitions between spinsplitted subbands, and, due to the peculiar energy dispersion relation, charge and spin currents are generated at zerobias voltage. We demonstrate that the generation of pure spin currents is possible under an appropriate choice of external control parameters.
TemperatureDependent Asymmetry Of The Nonlocal SpinInjection Resistance: Evidence For Spin Nonconserving Interface Scattering, Samir Garzon, Igor Žutić, Richard A. Webb
TemperatureDependent Asymmetry Of The Nonlocal SpinInjection Resistance: Evidence For Spin Nonconserving Interface Scattering, Samir Garzon, Igor Žutić, Richard A. Webb
Faculty Publications
We report nonlocal spin injection and detection experiments on mesoscopic CoAl_{2}O_{3}Cu spin valves. We have observed a temperaturedependent asymmetry in the nonlocal resistance between parallel and antiparallel configurations of the magnetic injector and detector. This strongly supports the existence of a nonequilibrium resistance that depends on the relative orientation of the detector magnetization and the nonequilibrium magnetization in the normal metal providing evidence for increasing interface spin scattering with temperature.
LongLived Spin Coherence States In Semiconductor Heterostructures, Yuriy V. Pershin Dr
LongLived Spin Coherence States In Semiconductor Heterostructures, Yuriy V. Pershin Dr
Faculty Publications
We study evolution of electron spin coherence having nonhomogeneous direction of spin polarization vector in semiconductor heterostructures. It is found that the electron spin relaxation time due to the D’yakonov Perel’ relaxation mechanism essentially depends on the initial spin polarization distribution. This effect has its origin in the coherent spin precession of electrons diffusing in the same direction. We predict a long spin relaxation time of a novel structure: a spin coherence standing wave and discuss its experimental realization.
Tb^{3+}Doped K Pb_{2}Br_{5}: LowEnergy Phonon MidInfrared Laser Crystal, U. N. Roy, R. H. Hawrami, Y. Cui, S. Morgan, A. Burger, K. C. Mandal, C. C. Noblitt, S. A. Speakman, K. Rademaker, S. A. Payne
Tb3+Doped K Pb2Br5: LowEnergy Phonon MidInfrared Laser Crystal, U. N. Roy, R. H. Hawrami, Y. Cui, S. Morgan, A. Burger, K. C. Mandal, C. C. Noblitt, S. A. Speakman, K. Rademaker, S. A. Payne
Faculty Publications
No abstract provided.
Data Management And Visualization Of XRay Diffraction Spectra From Thin Film Ternary Composition Spreads, I. Takeuchi, C. J. Long, O. O. Famodu, M. Murakami, Jason R. HattrickSimpers, G. W. Rubloff, M. Stukowski, K. Rajan
Data Management And Visualization Of XRay Diffraction Spectra From Thin Film Ternary Composition Spreads, I. Takeuchi, C. J. Long, O. O. Famodu, M. Murakami, Jason R. HattrickSimpers, G. W. Rubloff, M. Stukowski, K. Rajan
Faculty Publications
We discuss techniques for managing and visualizing xray diffraction spectrum data for thin film composition spreads which map large fractions of ternary compositional phase diagrams. An inhouse xray microdiffractometer is used to obtain spectra from over 500 different compositions on an individual spread. The MATLAB software is used to quickly organize the data and create various plots from which one can quickly grasp different information regarding structural and phase changes across the composition spreads. Such exercises are valuable in rapidly assessing the “overall” picture of the structural evolution across phase diagrams before focusing in on specific composition regions for detailed ...
Interphase Exchange Coupling In Fe/SmCo Bilayers With Gradient Fe Thickness, MingHui Yu, Jason R. HattrickSimpers, Ichiro Takeuchi, Jing Li, Z. L. Wang, J. P. Liu, S. E. Lofland, Somdev Tyagi, J. W. Freeland, D. Giubertoni, M. Bersani, M. Anderle
Interphase Exchange Coupling In Fe/SmCo Bilayers With Gradient Fe Thickness, MingHui Yu, Jason R. HattrickSimpers, Ichiro Takeuchi, Jing Li, Z. L. Wang, J. P. Liu, S. E. Lofland, Somdev Tyagi, J. W. Freeland, D. Giubertoni, M. Bersani, M. Anderle
Faculty Publications
We have fabricated Fe∕Sm–Co bilayers with gradient Fe thicknesses in order to systematically study the dependence of exchange coupling on the thickness of the Fe layer. The Fe layer was deposited at two different temperatures (150 and 300°C) to study the effect of deposition temperature on the exchange coupling. Magnetooptical Kerr effect and xray magnetic circular dichroism (XMCD) have been employed as nondestructive rapid characterization tools to map the magnetic properties of the gradient samples. Systematic enhancement in exchange coupling between the soft layer and the hard layer is observed as the soft layer thickness is decreased ...
Semiclassical Nonadiabatic Dynamics Using A Mixed WaveFunction Representation, Sophya V. Garashchuk, V. A. Rassolov, G. C. Schatz
Semiclassical Nonadiabatic Dynamics Using A Mixed WaveFunction Representation, Sophya V. Garashchuk, V. A. Rassolov, G. C. Schatz
Faculty Publications
Nonadiabaticeffects in quantum dynamics are described using a mixed polar/coordinate space representation of the wave function. The polar part evolves on dynamically determined potential surfaces that have diabatic and adiabatic potentials as limiting cases of weak localized and strong extended diabatic couplings. The coordinate space part, generalized to a matrix form, describes transitions between the surfaces. Choice of the effective potentials for the polar part and partitioning of the wave function enables one to represent the total wave function in terms of smooth components that can be accurately propagated semiclassically using the approximate quantum potential and small basis sets ...
Semiclassical Nonadiabatic Dynamics With Quantum Trajectories, Vitaly A. Rassolov, Sophya V. Garashchuk
Semiclassical Nonadiabatic Dynamics With Quantum Trajectories, Vitaly A. Rassolov, Sophya V. Garashchuk
Faculty Publications
Dynamics based on quantum trajectories with approximate quantum potential is generalized to nonadiabatic systems and its semiclassical properties are discussed. The formulation uses the mixed polarcoordinate space representation of a wave function. The polar part describes the overall time evolution of the wavefunction components semiclassically using the singlesurface approximate quantum potential. The coordinate part represents a complex“population” amplitude, which in case of localized coupling can be solved for quantum mechanically in an efficient manner. In the highenergy regime this is accomplished by using a small basis determined by the coupling between surfaces. An illustration is given for a typical ...