Compact cryogenic Kerr microscope for time-resolved studies of electron spin transport in microstructures

Rizo, P.; Pugžlys, Audrius; Liu, J.; Reuter, D.; Wieck, A. D.; Wal, van der Caspar; Loosdrecht, P.H.M. van

doi:10.1063/1.3046283

Cited by 6 publications

(6 citation statements)

References 20 publications

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“…An interesting direction is to explore whether confinement of such electron ensembles in micronscale device structures (as large quantum dots and wires) can be used to study spin dephasing anisotropy and suppression of spin dephasing due to confinement 22,67 . In addition, continuing our work with a microscope function in the setup allows for studying spin dynamics of 2DEG spins in transport channels with very high time resolution and micronscale spatial resolution 62 . Our results thereby provide a path to performing studies on heterojunction 2DEG channels with tunable spin-orbit effects and electron density, which is interesting for work on the Datta-Das spin-transistor concept 4 .…”

Section: Discussionmentioning

confidence: 99%

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Optical probing of spin dynamics of two-dimensional and bulk electrons in a GaAs/AlGaAs heterojunction system

et al. 2010

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We present time-resolved Kerr rotation measurements of electron spin dynamics in a GaAs/AlGaAs heterojunction system that contains a high-mobility two-dimensional electron gas (2DEG). Due to the complex layer structure of this material the Kerr rotation signals contain information from electron spins in three different layers: the 2DEG layer, a GaAs epilayer in the heterostructure, and the underlying GaAs substrate. The 2DEG electrons can be observed at low pump intensities, using that they have a less negative g-factor than electrons in bulk GaAs regions. At high pump intensities, the Kerr signals from the GaAs epilayer and the substrate can be distinguished when using a barrier between the two layers that blocks intermixing of the two electron populations. This allows for stronger pumping of the epilayer, which results in a shift of the effective g-factor. Thus, three populations can be distinguished using differences in g-factor. We support this interpretation by studying how the spin dynamics of each population has its unique dependence on temperature, and how they correlate with time-resolved reflectance signals. PACS numbers: 72.25.Fe, 72.25.Rb, 78.66.Fd, 78.67.Pt I.

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Section: Discussionmentioning

confidence: 99%

“…Secondly, we took TRKR data in an experiment where a microscope function 62 was included in the setup with Laser 1. In these experiments we measured with pump and probe spots with a diameter of 1.6 µm that could be focussed at different (non-overlapping) locations on the sample.…”

Section: Kerr Signals From the 2deg Populationmentioning

confidence: 99%

Optical probing of spin dynamics of two-dimensional and bulk electrons in a GaAs/AlGaAs heterojunction system

et al. 2010

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“…In-fact the Magneto-optical methods such as Faraday rotation and Kerr spectroscopy allows one to probe the local spin polarization along various points in the leads as well in the sample [100,101,102,103],which can be directly related to the spin-density polarization vector calculated in this article.…”

Section: Resultsmentioning

confidence: 99%

“…The formulation of the theory in terms of lead indices(or in mesoscopic language) is helpful to connect it with the experimentally measured local spinpolarization in the leads as well in the sample. In-fact the Magneto-optical methods such as Faraday rotation and Kerr spectroscopy allows one to probe the local spin polarization along various points in the leads as well in the sample [100,101,102,103],which can be directly related to the spin-density polarization vector calculated in this article.…”

Section: Discussionmentioning

confidence: 99%

Quantum non-Abelian hydrodynamics: Anyonic or spin–orbital entangled liquids, nonunitarity of scattering matrix and charge fractionalization

Pareek

2014

Int. J. Mod. Phys. B

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In this article we develop an exact(non-adiabatic,non-perturbative) density matrix scattering theory for a two component quantum liquid which interacts or scatters off from a generic spin-dependent quantum potential.The generic spin dependent quantum potential[eq. (1)] is a matrix potential, hence, adiabaticity criterion is ill-defined. Therefore the full matrix potential should be treated non-adiabatically. We succeed in doing so using the notion of vectorial matrices which allows us to obtain an exact analytical expression for the scattered density matrix ,̺sc [eq.(30)]. We find that the number or charge density in scattered fluid,Tr(̺sc), expressions in eqs. (32) depends on non-trivial quantum interference coefficients, Q αβ 0ijk which arises due to quantum interference between spin-independent and spin-dependent scattering amplitudes and among spin-dependent scattering amplitudes. Further it is shown that Tr(̺sc) can be expressed in a compact form [eq.(39)] where the effect of quantum interference coefficients can be include using a vector Q αβ which allows us to define a vector order parameter Q. Since the number density is obtained using and exact scattered density matrix, therefore, we do not need to prove that Q is non-zero. However for sake of completeness we make detailed mathematical analysis for the conditions under which the vector order parameter Q would be zero or non-zero.We find that in presence of spin-dependent interaction the vector order parameter Q is necessarily non-zero and is related to the commutator and anti-commutator of scattering matrix S with its dagger S † [eq. (78)]. It is further shown that Q = 0, implies four physically equivalent conditions,i.e, spin-orbital entanglement is non-zero, NonAbelian scattering phase ,i.e, matrices, scattering matrix is NonUnitary and the broken time reversal symmetry for scattered density matrix. This also implies that quasi particle excitation are anyonic in nature, hence, charge fractionalization is a natural consequence. This aspect has also been discussed from the perspective of number or charge density conservation, which implies i.e, Tr(̺sc) = Tr(̺in). On the other hand Q = 0 turns out to be a mathematically forced unphysical solution in presence of spin-dependent potential or scattering which is equivalent 1 to Abelian hydrodynamics ,Unitary scattering matrix, absence of spinspace entanglement, and preserved time reversal symmetry.We have formulated the theory using mesoscopic language, specifically, we have considered two terminal systems connected to spin-dependent scattering region, which is equivalent to having two potential wells separated by a generic spin-dependent potential barrier. The formulation using mesoscopic language is practically useful because it leads directly to the measured quantities such as conductance and spin-polarization density in the leads, however, the presented formulation is not limited to the mesoscopic system only, its generality has been stressed at various places in this article.

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“…Apart from using the photoelastic effect, another common modulation scheme in a MOKE microscope is the differential detection. In this scheme the reflected beam is split into two cross-polarised beams and collected by a differential photodetector with two balanced photodiodes [4,15,16,42]. Here we use the PEM modulation scheme because it has a better tolerance to misalignment, as the reflected light always stays in the central optical path without splitting.…”

Section: Moke Instrumentationmentioning

confidence: 99%

A low-temperature Kerr effect microscope for the simultaneous magneto-optic and magneto-transport study of magnetic topological insulators

Liu

Singh

Llandro

et al. 2019

Meas. Sci. Technol.

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Magneto-optical Kerr effect (MOKE) microscopy is a surface-sensitive probe of magnetisation with micron-sized lateral resolution. Here, we present a low-temperature, focused polar MOKE microscope for the simultaneous magnetooptical and magneto-transport measurements, which has a temperature range of 1.6-300 K and is equipped with a magnet capable of delivering a field of up to 9 T. In this microscope, all optical components are integrated in a free-standing probe, allowing for the straightforward incorporation into many non-optical cryostat systems. Two-dimensional magnetisation scans on patterned ferromagnetic [CoFeB/Pt] n films demonstrate a magnetisation sensitivity of 10 µrad (Kerr angle) and a spatial resolution of 2.2 µm. The combination of optical and electrical measurements provides complementary temperature-dependent information, as demonstrated by the study of magnetic topological insulator thin films with out-of-plane magnetic anisotropy. Using this complementary approach, we study the effects of a secondary phase in Cr and V co-doped Sb 2 Te 3 thin films, which show a combination of weak antilocalization and anisotropic magnetoresistance effects above 70 K. Our results highlight the virtue of MOKE and electrical transport to optimise exotic topological magnetic materials, paving the way for energy-efficient spintronic devices.

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Compact cryogenic Kerr microscope for time-resolved studies of electron spin transport in microstructures

Cited by 6 publications

References 20 publications

Optical probing of spin dynamics of two-dimensional and bulk electrons in a GaAs/AlGaAs heterojunction system

Optical probing of spin dynamics of two-dimensional and bulk electrons in a GaAs/AlGaAs heterojunction system

Quantum non-Abelian hydrodynamics: Anyonic or spin–orbital entangled liquids, nonunitarity of scattering matrix and charge fractionalization

A low-temperature Kerr effect microscope for the simultaneous magneto-optic and magneto-transport study of magnetic topological insulators

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