Detection of spin polarized currents in quantum point contacts via transverse electron focusing

Reynoso, Andrés A.; Usaj, Gonzalo; Balseiro, C. A.

doi:10.1103/physrevb.75.085321

Cited by 38 publications

(45 citation statements)

References 31 publications

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“…1, while the asymmetry in the sub-peak intensity is a direct manifestation of spin polarization. 18,19 The split in the focusing peak persists up to 2G 0 which is consistent with the experimental observation of 1.7G 0 in the conductance measurement which was attributed to spontaneous spin polarisation in the 1D system. 12,24 The two spin states become degenerate at high injector conductance, resulting in a single broad peak for injector conductance 3G 0 .…”

supporting

confidence: 77%

“…The splitting of the first peak, not for the second peak, is predicted to be a sign of the spin-orbit interaction (SOI). 18,19 It may be noted that the observed splitting of 5.5 mT (after scaling against L, it becomes 6.3 mT for 90 geometry) is much smaller than the 40 mT splitting in GaAs hole gas 20,21 or 60 mT in InSb electron gas, 22 which is expected for low SOI in n-GaAs. We made sure that the observed effect is not due to the disorder induced electron branching, 23 because the splitting of the first peak remained preserved when we swapped the role of the injector and the detector (see the discussion in the supplementary material).…”

mentioning

confidence: 98%

“…13,14 The origin of spingap in the 1D system has aroused a great interest to explain the "0.7 anomaly" in the framework of spin correlation between the 1D electrons. [13][14][15][16] The spin polarization in a 1D quantum wire 13,14 can be measured by means of transverse electron focusing (TEF), [17][18][19] where the height of each focusing peak is proportional to the population of detected electrons. It has been confirmed experimentally in a GaAs hole gas 20,21 and an InSb electron gas 22 that the first focusing peak splits into two sub-peaks and each peak is associated with a spin of an electron.…”

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confidence: 99%

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Direct observation of exchange-driven spin interactions in one-dimensional system

Yan

Kumar

Thomas

et al. 2017

Applied Physics Letters

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We present experimental results of transverse electron focusing measurements performed on an n-type GaAs based mesoscopic device consisting of one-dimensional (1D) quantum wires as injector and detector. We show that non-adiabatic injection of 1D electrons at a conductance of e2h results in a single first focusing peak, which transforms into two asymmetric sub-peaks with a gradual increase in the injector conductance up to 2e2h, each sub-peak representing the population of spin-state arising from the spatially separated spins in the injector. Further increasing the conductance flips the spin-states in the 1D channel, thus reversing the asymmetry in the sub-peaks. On applying a source-drain bias, the spin-gap, so obtained, can be resolved, thus providing evidence of exchange interaction induced spin polarization in the 1D systems.

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confidence: 77%

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confidence: 98%

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confidence: 99%

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Direct observation of exchange-driven spin interactions in one-dimensional system

Yan

Kumar

Thomas

et al. 2017

Applied Physics Letters

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“…Yet another method detects the polarized current in quantum-point contacts via transverse electron focusing. 71 …”

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confidence: 99%

Filtering and analyzing mobile qubit information via Rashba–Dresselhaus–Aharonov–Bohm interferometers

et al. 2011

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Spin-1/2 electrons are scattered through one or two diamond-like loops, made of quantum dots connected by one-dimensional wires, and subject to both an Aharonov-Bohm flux and (Rashba and Dresselhaus) spin-orbit interactions. With some symmetry between the two branches of each diamond, and with appropriate tuning of the electric and magnetic fields (or of the diamond shapes) this device completely blocks electrons with one polarization, and allows only electrons with the opposite polarization to be transmitted. The directions of these polarizations are tunable by these fields, and do not depend on the energy of the scattered electrons. For each range of fields one can tune the site and bond energies of the device so that the transmission of the fully polarized electrons is close to unity. Thus, these devices perform as ideal spin filters, and these electrons can be viewed as mobile qubits; the device writes definite quantum information on the spinors of the outgoing electrons. The device can also read the information written on incoming polarized electrons: the charge transmission through the device contains full information on this polarization. The double-diamond device can also act as a realization of the Datta-Das spin field-effect transistor.

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“…The QPC can be tuned to control the number of transmitting channels and thus the critical current of the junction [3,4,5,12,13]. On the other hand, the QPC with SO coupling may act as a spin filter producing spin-polarized currents when embedded in a circuit with normal leads [14,15,16]. The normal current also generates an in-plane magnetization-perpendicular to the current -as well as out-of-plane spin-Hall textures [17].…”

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Anomalous Josephson Current in Junctions with Spin Polarizing Quantum Point Contacts

Reynoso

Usaj²,

Balseiro³

et al. 2008

Phys. Rev. Lett.

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194

182

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We consider a ballistic Josephson junction with a quantum point contact in a two-dimensional electron gas with Rashba spin-orbit coupling. The point contact acts as a spin filter when embedded in a circuit with normal electrodes. We show that with an in-plane external magnetic field an anomalous supercurrent appears even for zero phase difference between the superconducting electrodes. In addition, the external field induces large critical current asymmetries between the two flow directions, leading to supercurrent rectifying effects. PACS numbers: 74.45.+c, 71.70.Ej, 72.25.Dc, 74.50.+r Josephson junctions (JJ) are the basic building blocks for superconducting electronics with applications that range from SQUID magnetometers to possible quantum computing devices. In superconductor-normal metal-superconductor (S-N-S) junctions the supercurrent flow is due to the Andreev states-a coherent superposition of electron and holes states. These states depend on the electronic structure of the normal material and on the properties of the S-N interface [1,2,3,4]. Modern technologies based on two dimensional electron gases (2DEGs) [5,6] or nanowires [7] allow for a precise control of such electronic properties, and thus of the JJ characteristics. Moreover, spin-orbit (SO) effects offer new alternatives to control the spin and charge transport [8,9].Superconducting rectifiers are among the new devices proposed and studied during the last few years. Most of these proposals are based on the dynamics of vortices [10,11]. Here we show that in systems with SO-coupling rectifying properties can be obtained by controlling the spin of the Andreev states. To this end we consider a ballistic JJ with a quantum point contact (QPC) in a 2DEG with SO interaction. The QPC can be tuned to control the number of transmitting channels and thus the critical current of the junction [3,4,5,12,13]. On the other hand, the QPC with SO coupling may act as a spin filter producing spin-polarized currents when embedded in a circuit with normal leads [14,15,16]. The normal current also generates an in-plane magnetization-perpendicular to the current -as well as out-of-plane spin-Hall textures [17]. Both effects are maximized at the core of the QPC [18]. As the SO-coupling preserves time-reversal symmetry (TRS), we expect that these peculiarities of the transmitting channels do not harm the Josephson effect when the leads become superconducting. However, the Josephson current itself breaks the TRS and, as we show below, it reveals striking effects of the SO-coupling. For example, the supercurrent generates spin polarization in the 2DEG [19] and the QPC in a similar way normal current does [17,18]. This is due to the distinctive spin texture of each Andreev state that contributes to the local magnetization in a supercurrent-carrying state.More striking effects take place if an external in-plane magnetic field is applied. Its effect on the supercurrent characteristics depends on the nature of the junction. In the absence of SO-coupling, the Zeeman field ...

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Detection of spin polarized currents in quantum point contacts via transverse electron focusing

Cited by 38 publications

References 31 publications

Direct observation of exchange-driven spin interactions in one-dimensional system

Direct observation of exchange-driven spin interactions in one-dimensional system

Filtering and analyzing mobile qubit information via Rashba–Dresselhaus–Aharonov–Bohm interferometers

Anomalous Josephson Current in Junctions with Spin Polarizing Quantum Point Contacts

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