Electric control of spin transport in GaAs (111) quantum wells

We have studied the lateral transport of electron spins in GaAs (111) quantum wells (QWs) under a transverse electric field Ez. A tightly focused (cf. Fig. 1a), circularly polarized laser beam generates a narrow ensemble of electron-hole (e-h) pairs with spins preferentially oriented along the direction perpendicular to the QW plane. During their expansion along the QW, the e-h pairs recombine emitting photons, whose polarization is settled by the orientation direction of the electron spin vector. We show by time and spatially-resolved, polarization-dependent photoluminescence measurements that the applied electric field enables the transport of out-of-plane spin polarized electrons over distances exceeding 10 μm. The long spin transport distance is attributed to the electrically induced cancellation of spin precession around the spin-orbit field as the electrons move away from the generation spot.

Fig. 1(a) Experimental setup. A tightly focused laser beam generates an ensemble of spin polarized electrons. After expanding along the QW, they recombine with holes (not shown) emitting photons. The polarization of the emitted light depends on the orientation of the electron spin vector. (b) Out-of-plane spin polarization of the electron ensemble as a function of the radial distance from the generation spot for different applied transverse electric fields, Ez.

The control of the electron spin vector is essential for the efficient processing of quantum information in semiconductors. For this purpose, electric fields can manipulate the electron spin vector in III-V semiconductors via the spin-orbit (SO) interaction. The SO-coupling, however, can also induce spin dephasing in an electron ensemble, thus erasing the information stored in the spin degree of freedom. We have previously shown that GaAs quantum wells (QWs) grown along the [111] direction are particularly interesting for the steering of the spin dynamics of an electron ensemble [1-3]. Due to the special symmetry of the SO-interaction at low temperatures, an electric field transverse to the QW plane, Ez, can suppress the intrinsic SO-coupling acting on the electron ensemble and lead to spin dephasing times exceeding 100 ns.

A further important requirement for the efficient use of the spin degree of freedom is the ability to move carriers from one point of the semiconductor structure to another without losing their spin polarization. This requires not only long spin dephasing times but also good spin transport properties. In this contribution, we report experimental studies of both charge and spin transport in a GaAs (111) QW under the effect of Ez. In our experiments, a cloud of e-h pairs with their spins preferentially polarized along the z direction is optically generated by a tightly focused laser beam, cf. Fig. 1(a). We then monitor their lateral expansion by collecting the photons emitted when the e-h pairs recombine, and analyzing their polarization with time and spatial resolution. We show that the appropriate value of Ez enables the transport of electron spins polarized along the out-of-plane direction over distances exceeding 10 μm, cf. Fig. 1(b). The long spin transport distance is attributed to the cancellation of spin precession around the SO-field as the electrons move away from the generation spot.

4 Autor A. Hernández-Mínguez , K. Biermann , R. Hey , P. V. Santos
Titel

Electric control of spin transport in GaAs(111) quantum wells

Source Phys. Rev. B , 94 , 125311 ( 2016 )
DOI : 10.1103/PhysRevB.94.125311 | Download: PDF | 2717 Cite : Bibtex RIS
A. Hernández-Mínguez, K. Biermann, R. Hey, and P. V. Santos

3 Autor A. Hernández-Mínguez , K. Biermann , R. Hey , P. V. Santos
Titel

Spin transport and spin manipulation in GaAs (110) and (111) quantum wells

Source Phys. Status Solidi B , 251 , 1736 ( 2014 )
DOI : 10.1002/pssb.201350202 | 2535 Cite : Bibtex RIS
A. Hernández-Mínguez, K. Biermann, R. Hey, and P. V. Santos

2 Autor A. Hernández-Mínguez , K. Biermann , R. Hey , P. V. Santos
Titel

Electrical suppression of spin relaxation in GaAs(111)B quantum wells

Source Phys. Rev. Lett. , 109 , 266602 ( 2012 )
DOI : 10.1103/PhysRevLett.109.266602 | Download: PDF | 2375 Cite : Bibtex RIS
A. Hernández-Mínguez, K. Biermann, R. Hey, and P. V. Santos

1 Autor K. Biermann , A. Hernández-Mínguez , R. Hey , P. V. Santos
Titel

Electrically tunable electron spin lifetimes in GaAs(111)B quantum wells

Source J. Appl. Phys. , 112 , 083913 ( 2012 )
Download: PDF | 2364 Cite : Bibtex RIS
K. Biermann, A. Hernández-Mínguez, R. Hey, and P. V. Santos