Wigner crystallization, spontaneous electron polarization in zero magnetic field, 0. Direct observation of spin polarization in gaas quantum wires by. We show that the temperature dependence of the polarization signal from 2 to 150 k can be understood in terms of a crossover from excitonic to freeelectron spin relaxation in the quantum well. The total energy of a quasionedimensional electron system was calculated using the density functional theory. An analysis of the relative contributions due to linear, quadratic, and cubic dresselhaus spin orbit terms on the energy levels, spin splitting, and spin polarization has been carried out. We performed the resistivelydetected nuclear magnetic resonance rdnmr to study the electron spin polarization in the nonequilibrium quantum hall regime. It is found that the spin polarization direction can be switched by changing the direction of the external current. Spinpolarized quantum transport in mesoscopic conductors. Spin is believed to play an important role in these e ect. Ho and colleagues design a clever and innovative setup which combines realspace charge and spin detection together with conductance measurements to demonstrate this largely elusive, exotic wignerlike phase and its spin properties in 1d quantum wires.
Enhancement of spin polarization by chaos in graphene. Winmostar tutorial quantum espresso spin polarization v7. Dec 04, 2015 currently, there is a great deal of interest in the quantum wires qw properties that have been studied less than those of quantum wells and quantum dots. Such a quantum spin chain with a variety of electrically controllable spin phases in solid.
The interplay between intrinsic and rashba spin orbit interactions induced by an electric field leads to helical modes, giving rise to spin filtering in timereversalinvariant systems. Kokurintuning outofplane spin polarization using inplane magnetic fields in a quasionedimensional quantum wire embedded in 110 plane sun jinfang. The critical electron density below which electrons are in spin polarized state is estimated. Complete spin polarization of electrons in semiconductor layers and quantum dots v. First the basic concept of spin polarized transport and the calculation of the current spin polarization is demonstrated in a.
Spin, polarization, and mixed states polarization spin mixed state questions bells inequality. An individual photon can be described as having right or left circular polarization, or a superposition of the two. A number of recent experiments report spin polarization in quantum wires in the absence of magnetic fields. Spontaneous spin polarization of electrons in quantum wires. Electrons on the two dimensional quantum wire can be approximated as a two dimensional electron gas 2deg. Spinpolarized transport and spin seebeck effect in triple. Densitydependent spin polarization in ultralowdisorder. However, the field can adversely impact the induced superconductivity and places.
Here, we theoretically investigate this problem with the help of a quantum master. A symmetric bias is applied to the second set of gates near the drain and is varied to maximize the amount of spin polarization in the channel. Potential applications of all electric spin valves made of. In the absence of a magnetic field, we have found that ferromagnetic state occurs in the quantum wires. Spin injection and relaxation in ferromagnetsemiconductor. Spin polarization direction switch based on an asymmetrical. Externally controlled high degree of spin polarization and spin.
Feb 01, 2010 we demonstrate detection of spin polarization in a quantum wire utilizing a side coupled quantum dot. We report theoretical modeling of spin dependent quantum transport properties of dangling bond wires dbws on the si1002. Spin polarization in modulationdoped gaas quantum wires. Jan 17, 20 a scheme for a spin polarization direction switch is investigated by studying the spin dependent electron transport of an asymmetrical quantum wire with rashba spin orbit coupling. We study the spindependent electronic and thermoelectric transport through a structure composed of triple quantum dots tqds coupled to. One says the photon possesses a polarization angular momentum quantum number j 1 with. Pdf allelectric allsemiconductor spin fieldeffect transistors. Introduction to quantum mechanics 1 polarization of light 1. The mechanism driving the polarization is the exchange energy. Winmostar tutorial quantum espresso spin polarization v8.
In twodimensional hole gases there is experimental evidence of a. Crystallographic plane tuning of charge and spin transport in. In light direction of oscillation of its electric field determines lights state of polarization. In twodimensional holegasesthere is experimental evidence of a. If we were to visualize lights electric wave oscillations same as a propagating water wave, then. Between 70 and 150 k, the spin polarization increases with temperature over a wide range of bias voltages. Spin polarization and conductance in quantum wires under. Detection of spin polarization in a quantum wire having identi. Spin polarization and conductance in quantum wires under external bias potentials hans lind 20100301 lithifmaex102224se department of physics, chemistry and biology linkopings universitet, se581 83 linkoping, sweden. Theoretical study of dynamic electronspinpolarization. Biascontrolled spin polarization in quantum wires nasaads. Spin, polarization, and mixed states quantum measurement.
By the photoinduced electron transfer, the quantum mixed chargeseparate state is generated in acceptordonorradical triad adr. Our samples consist of splitgate devices defined by electronbeam lithography on a hall bar etched from a gaas al x ga 1 x as heterostructure. Spin polarization and temperature dependence of electron. The conditions for a spontaneous spin polarization in a quantum wire positioned in a zero magnetic. Data obtained using a bias spectroscopy technique are consistent with the spin gap widening further as the fermi level is increased. Nonequilibrium nuclear spin polarization affects the electron energy spectrum making it time dependent. However, a fully polarized state is not achieved as expected from a classical rate equation. Shulman1, arijeet pal1, vladimir umansky2, emmanuel i.
The phase diagram of the transition into the spin polarized state is constructed. In this device, the first pair of sgs, near the source, is asymmetrically biased to create spin polarization in the qpc channel. Pdf optical probing of the spin polarization of the nu5. We demonstrate that a sourcedrain bias creates a fully spinpolarized current as the 0. Matveev materials science division, argonne national laboratory, argonne, illinois 60439, usa dated. However,the spin polarization of the transmitted electrons varies as a function of the.
The theory of the 2deg has been studied thoroughly in the past1921. Spinorbitinduced spindensity wave in a quantum wire. Spontaneous spin polarization in quantum wires nasaads. Specifically, we study the combined effect of external magnetic field, nuclear spin polarization, and rashba spin orbit interaction on the conductance of a quantum wire. Enhanced negative nonlocal conductance in an interacting. We demonstrate that a sourcedrain bias creates a fully spin polarized current as the 0. The studies of the spontaneous spin polarization in quantum wires that have been carried. Quantum limit for nuclear spin polarization in semiconductor. A single spin polarized dangling bond center dbc near the dbw may strongly affect transport as characterized by antiresonances or dips in the transmission spectra. Coulomb effects on the spin polarization in quantum wires. Exciton spin polarization in magnetic semiconductor. Berggren and wang 11 have taken into account exchange interaction between electrons and by solving the kohnsham equations selfconsistently found spontaneous spin polarization in a quantum wire. The mechanism of the unique dynamic electron polarization of the quartet s 32 high spin state via a doubletquartet quantum mixed state and detail theoretical calculations of the population transfer are reported.
Observation of a onedimensional spinorbit gap in a quantum wire. Photon polarization is the quantum mechanical description of the classical polarized sinusoidal plane electromagnetic wave. Imaging the zigzag wigner crystal in confinementtunable quantum. Signatures of majorana zero modes mzms have been observed in semiconductor nanowires nws with a strong spin orbital interaction soi with proximityinduced superconductivity. Spin polarization conductance quantum wire sammanfattning abstract we study the spin polarization and conductance in infinitely long quasi onedimensional quantum wires under various conditions in an attempt to reproduce and to explain some of the anomalous conductance features as seen in various experiments. We devise an approach to measure the polarization of nuclear spins via conductance measurements. New interaction effects in quantum point contacts at high. Theory let us consider a semiconductor quantum wire with a rectangular cross section, as. The quantum mechanical consideration carried out analytically in the context of the hartreefockslater approximation with localized exchange potential shows that consideration of the electronelectron interaction in a quantum wire with an arbitrary carrier density leads to spontaneous polarization of the quasi1d electronic gas in zero. Polarization of nuclear spins from the conductance of quantum. Detection of spin polarized currents in quantum point. Spin polarized current generation from quantum dots. By applying inplane magnetic fields, spin split conducting channels are formed and produce spin polarization in the wire. Pdf spontaneous spin polarization in quantum wires.
Importantly, it appears that the spin gap is not constant but a function of the electron density. Biascontrolled spin polarization in quantum wires aip publishing. The magnetic fields also create zeeman split spin levels in the dot and these states are used as a spin polarization detector. Pdf exciton spin polarization in magnetic semiconductor. Spin dephasing or spin depolarization in the wire is caused by dyakonovperel relaxation associated with bulk inversion asymmetry dresselhaus spin orbit coupling and structural inversion asymmetry rashba spin orbit coupling. Bias voltage dependence of the electron spin depolarization.
Universal control of the twoelectron qubit is then demonstrated using quantum state tomography. The qwr is readily formed by applying negative voltages on gate w v. Despite this seemingly simple way to create a spin polarized current, this effect has. Quenching of dynamic nuclear polarization by spinorbit.
December 11, 20 a number of recent experiments report spin polarization in quantum wires in the absence of arxiv. Spin quantum beats of freeelectron larmor precession are measured by time resolved photoluminescence spectroscopy and yield an extreme anisotropy of the electron land6 gfactor in quantum wires. Aug 01, 2006 we will show that the evolution of this structure in b provides intriguing new evidence that a fully spin polarised state can be induced in a quantum wire at b 0 simply by applying a large dcbias. Pdf biascontrolled spin polarization in quantum wires. When a sourcedrain bias lifts the momentum degeneracy, the dc measurements show that it is possible to achieve a unidirectional ferromagnetic order and this ordered spin array is destroyed once transport in both directions commences. Quantum control and measurement of atomic spins in. Spin polarized current generation from quantum dots without. We apply polarization resolved photoluminescence spectroscopy to measure the spin polarization of a two dimensional electron gas in perpendicular magnetic field. A spin energy gap is indicated by the presence of a feature in the range 0. Equivalently, a photon can be described as having horizontal or vertical linear polarization, or a superposition of the two. Externally controlled high degree of spin polarization and. Spin polarized transport as measured by superconducting. Spin transport in ferromagnetinsb nanowire quantum devices. Request pdf spin polarization in modulationdoped gaas quantum wires the silences of the archives, the reknown of the story.
Allelectric and allsemiconductor spin field effect transis tors core. Recently one of the authors of us has also shown that controlled spin dependent transport can be obtained through a magnetic quantum wire. Decoherence of transported spin in multichannel spinorbitcoupled. The generation and control of spinpolarized currents, in. Spin orbitinduced spin density wave in a quantum wire jianmin sun, suhas gangadharaiah, and oleg a. Theory let us consider a semiconductor quantum wire with a rectangular cross section, as shown in fig. Pdf allelectrical injection and detection of a spin. In the vicinity of filling factor nu52, we observe a sharp discontinuity in the energy. Spontaneous spin polarization in quantum wires sciencedirect. Quenching of dynamic nuclear polarization by spin orbit coupling in gaas quantum dots john m. Universal quantum control of twoelectron spin quantum. In onedimensional systems quantum wires and quantum point contactsa puzzling socalled 0. The depolarization rate is found to depend strongly on the initial polarization of the spin.
Using spin bias to manipulate and measure spin in quantum dots. First consider infinitesimal bias at temperature t. Petukhov physics department, south dakota school of mines and technology. Detection of spin polarization in a quantum wire sciencedirect. These observations are in apparent contradiction with the liebmattis theorem, which forbids spontaneous spin polarization in one dimension. Detection of spin polarization in quantum point contacts. For a photon, on the other hand, the intrinsic angular momentum is often called spin or helicity, but could be called circular polarization. The rashba spin orbit interaction can also be generated by spatially varying.
The electron spin polarization shows minimum value around the threshold voltage of the dynamic nuclear. January 7, 2008 minor correction january 16, 2008 physics 225315 j. Polarization of nuclear spins from the conductance of. We show that sufficiently strong interactions between electrons induce deviations from the strictly onedimensional geometry and indeed give rise. Jul 23, 2008 we demonstrate that a sourcedrain bias creates a fully spin polarized current as the 0. By measuring the knight shift, we derive sourcedrain bias voltage dependence of the electron spin polarization in quantum wires. Spontaneous spin polarization in quantum point contacts. Starykh department of physics, university of utah, salt lake city, utah 84112, usa received 6 november 2006. Energy dispersion relations of spinsplit subbands in a.
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