Search for spin-polarized photoemission from GaAs using light with orbital angular momentum

Abstract

Laser light with photon energy near the bandgap of GaAs and in LaguerreGaussian modes with different amounts of orbital angular momentum was used to produce photoemission from unstrained GaAs. The degree of electron spin polarization was measured using a micro-Mott polarimeter and found to be consistent with zero with an upper limit of ~3% for light with up to ±5ħ of orbital angular momentum. In contrast, the degree of spin polarization was 32.3±1.4% using circularly-polarized laser light at the same wavelength, which is typical for bulk GaAs photocathodes.

Insensitivity of spin dynamics to the orbital angular momentum transferred from twisted light to extended semiconductors

“…Our central finding is that, rather unexpectedly, the spin dynamics of the photo-excited electrons differs only slightly after excitation with light with and without OAM in the limit of large quantum disks, becoming insensitive to the OAM content of the twisted light beam for extended quantum wells. This result is consistent with the outcome of recent experiments which did not show traces of the OAM transferred from twisted light to bulk GaAs in spin-resolved photoemission measurements [29].Analytically, we find that the Rashba interaction, while conserving the total angular momentum of the electrons, has matrix elements which are independent of the OAM quantum number in the (k-space) quasi-continuum limit. As a consequence, the induced spin dynamics is almost identical, in particular, for twisted light with components of the OAM in the growth direction l = +|l| and l = −|l|.…”

“…Recently, the theoretical foundation of the optical excitation of solids and nanostructures with twisted light has been established [19][20][21][22][23][24][25][26][27], and experimental studies with twisted light on semiconductors have been carried out [28,29].…”

“…Bh, 78.20.Ls, 78.40.Fy, 42.50.Tx Light with orbital angular momentum (OAM), referred to as twisted light, is a relatively new field of research which has become increasingly popular [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] since Allen et al showed how twisted light beams can be easily generated from conventional laser beams [18]. Recently, the theoretical foundation of the optical excitation of solids and nanostructures with twisted light has been established [19][20][21][22][23][24][25][26][27], and experimental studies with twisted light on semiconductors have been carried out [28,29].One motivation for such studies is the prospect of using the large amounts of angular momentum that twisted light can carry in order to control the spin dynamics of electrons, thus adding a flexible tool to the active field of spin control [30][31][32][33][34][35][36][37][38][39]. In this context two different mechanisms need to be distinguished.…”

Formulation of the twisted-light–matter interaction at the phase singularity: The twisted-light gauge

“…The research in TL spans several areas, such as the generation of beams [4,5], the interaction of TL with atoms and molecules [6,7] or with condensed matter [8][9][10][11][12][13][14][15][16][17][18][19][20]. TL has already proved to be useful in applications.…”

Discerning on a sub-optical-wavelength the attosecond time delays in electron emission from magnetic sublevels by optical vortices

“…The time delay carry atomic-scale information on the orbital position in the beam spot. Including spin-orbital coupling, e.g., as done in [85] should yield spin-dependent time delays offering a tool for polarized electron burst [86] by short OAM pulses. Combined with the possible spatial resolution on the magnetic states, this may offer a novel technique for spatio-temporal mapping of spin dynamics.…”