Spin-Orbit Symmetries of Conduction Electrons in Silicon

Li, Pengke; Dery, Hanan

doi:10.1103/physrevlett.107.107203

Cited by 93 publications

(134 citation statements)

References 34 publications

Supporting

Mentioning

128

Contrasting

Order By: Relevance

“…This process takes place via an intervalley → X → L phonon-assisted momentum scattering, as the X and XL scattering rates are much higher than the L one [21]. We suggest that this process could strongly depolarize the carriers by efficient spin-flip relaxation due to the spin hotspot on the square face of the BZ, whose center is in the X point, as pointed out for the case of Si [22]. For higher photon energies (∼2.3 eV), the photogeneration process takes place at the L point of the BZ.…”

mentioning

confidence: 94%

Wide-range optical spin orientation in Ge from near-infrared to visible light

et al. 2014

View full text Add to dashboard Cite

Ge-based spin-photodiodes have been employed to investigate the spectral dependence of optical spin orientation in germanium, in the range 400-1550 nm. We found the expected maximum in the spin polarization of photocarriers for excitation at the direct gap in (1550 nm) and a second sizable peak due to photogeneration in the L valleys (530 nm). Data suggest distinct spin depolarization mechanisms for excitation at and L, with shorter spin relaxation times whether the X point is involved. These devices can be used as integrated photon-helicity detectors over a wide spectral range. Spin-optoelectronics is a novel branch of semiconductor spintronics, aiming at adding a new degree of freedom to optoelectronics: the photon helicity. Exploiting the interplay between the photon angular momentum and the spin of electrons, integrated emitters (spin-LEDs) and detectors (spin photodiodes) of circularly polarized light have been proposed. Although GaAs is traditionally the material of choice for spin optoelectronics, because of its direct gap allowing for efficient conversion between light and spin polarization, recently Ge has attracted a considerable attention. In fact, thanks to the inversion symmetry of the crystal and the related absence of the D Yakonov-Perel spin scattering mechanism, Ge presents a longer spin coherence time than the one of GaAs. Spin manipulation [1], spin transport [2], spin optical pumping in the infrared [3][4][5][6][7], and electrical spin injection [8] in Ge have been reported. In our previous works [9,10], we demonstrated the room temperature operation of spin-PDs based on fully epitaxial Fe/MgO/Ge(001) heterostructures, working at 0.95 eV [11,12]. However, there is still a poor understanding of electrons and holes optical spin orientation in Ge, especially at photon energies much higher than the direct gap (0.8 eV). The optical spin orientation in Ge over a wide spectral range has been theoretically investigated by Rioux and Sipe [13]. However, no experimental data for excitation far from the point of the Brillouin zone (BZ) have been reported so far. Even for GaAs, only very recently the photon energy dependence of optical spin orientation well above the absorption edge has been reported [14].In this Rapid Communication, we report on the spectral dependence of the optical spin orientation in Ge at room temperature and over a wide spectral range (400-1550 nm, corresponding to 3.1-0.8 eV), via measurements of the helicitydependent photocurrent on Ge-based spin PDs. Surprisingly enough, the maximum sensitivity to photon helicity is observed far away from the direct gap (0.8 eV), where optical pumping is supposed to produce the highest initial spin polarization. Indeed, the helicity-dependent photocurrent variation indicates a first peak around 1500 nm (0.8 eV) and then an absolute maximum of about 10% at ∼530 nm (∼2.3 eV), corresponding to optical pumping in the L valley of the Ge band structure, * christian.rinaldi@polimi.it as shown in Fig. 1(a). Fitting of our data within a simple diffusive m...

show abstract

mentioning

confidence: 94%

Wide-range optical spin orientation in Ge from near-infrared to visible light

et al. 2014

View full text Add to dashboard Cite

show abstract

“…This requirement has highlighted solid-state spin systems as a natural choice for quantum bits (qubits). [3][4][5] Within this area, Si has been known for its extraordinarily long coherence times, [6][7][8][9][10][11][12] thanks to the absence of piezoelectric electron-phonon coupling, 13 weak spinorbit coupling 14,15 , and nuclear-spin free isotopes, allowing removal of the hyperfine interaction by isotopic purification. 16 As a result, Si spin QC has emerged as an active subfield of modern condensed matter physics.…”

Section: Introductionmentioning

confidence: 99%

Coherent electrical rotations of valley states in Si quantum dots using the phase of the valley-orbit coupling

Culcer

2012

Phys. Rev. B

View full text Add to dashboard Cite

A gate electric field has a small but non-negligible effect on the phase of the valley-orbit coupling in Si quantum dots. Finite interdot tunneling between valley eigenstates in a double quantum dot is enabled by a small difference in the phase of the valley-orbit coupling between the two dots, and it in turn allows controllable rotations of two-dot valley eigenstates at a level anticrossing. We present a comprehensive analytical discussion of this process, with estimates for realistic structures.

show abstract

“…Cheng's results agree very well with experiments. Additionally, two very recent papers [26,27] used analytical models to describe the symmetry of the electron spin-phonon interactions in silicon in detail. In contrast to that, the use of fully first-principles DFT and DFPT here allows truly predictive parameter-free calculations and additionally enables calculation of impurity scattering effects, for which no previous work exists.…”

mentioning

confidence: 99%

Full First-Principles Theory of Spin Relaxation in Group-IV Materials

Restrepo

Windl

2012

Phys. Rev. Lett.

View full text Add to dashboard Cite

We present a generally applicable parameter-free first-principles method to determine electronic spin relaxation times and apply it to the technologically important group-IV materials silicon, diamond and graphite. We concentrate on the Elliott-Yafet mechanism, where spin relaxation is induced by momentum scattering off phonons and impurities. In silicon, we find a ∼ T −3 temperature dependence of the phonon-limited spin relaxation time T1 and a value of 4.3 ns at room temperature, in agreement with experiments. For the phonon-dominated regime in diamond and graphite, we predict a stronger ∼ T −5 and ∼ T −4.5 dependence that limits T1 (300 K) to 180 and 5.8 ns, respectively. A key aspect of this study is that the parameter-free nature of our approach provides a method to study the effect of any type of impurity or defect on spin-transport. Furthermore we find that the spin-mix amplitude in silicon does not follow the E −2 g band gap dependence usually assigned to III-V semiconductors but follows a much weaker and opposite E 0.67 g dependence. This dependence should be taken into account when constructing silicon spin transport models.The physical roadblocks looming in the charge-based semiconductor device technology require paradigmshifting approaches to create new logic devices capable of lower power consumption and higher performance. This has motivated a search for new alternative logic variables, among which the spin of electrons is a natural candidate, which needs to be efficiently and reliably injected, transported, and detected. Although extensive studies have been done in direct-gap materials, the understanding of spin-transport and spin-life time dependence in the technologically relevant group-IV materials is surprisingly incomplete. Silicon and the carbon polytypes diamond and graphite are particularly relevant because long spin relaxation times can be expected in materials with inversion symmetry and low atomic number Z. For those, the main spin-relaxation mechanism at high temperatures is the Elliott-Yafet (EY) mechanism mediated through spin-orbit coupling [1,2], which scales as Z 2 .Silicon, an attractive potential spintronics material due to its compatibility with current technologies, has a relatively large spin orbit-coupling (44 meV) [3]. Nevertheless, Lepine's electron spin resonance (ESR) measurements [4,5], recently confirmed for low temperatures by Appelbaum et al. [6,7], found for its spin relaxation time T 1 a value of 7 ns at room temperature, which puts it well within the usable range. The experimental situation is less clear for carbon, whose lower Z-number promises longer spin relaxation times. Diamond with a spin-orbit coupling of 13 meV [8] is especially expected to have a long electronic spin relaxation time, which however has never been measured. For graphite, the most recent experimental data from 1961 [9, 10] suggest a large range for T 1 between 1-300 ns. For both diamond and graphite, no reliable theoretical predictions have been reported. Finally, the E −2 g dependence of th...

show abstract

Spin-Orbit Symmetries of Conduction Electrons in Silicon

Cited by 93 publications

References 34 publications

Wide-range optical spin orientation in Ge from near-infrared to visible light

Wide-range optical spin orientation in Ge from near-infrared to visible light

Coherent electrical rotations of valley states in Si quantum dots using the phase of the valley-orbit coupling

Full First-Principles Theory of Spin Relaxation in Group-IV Materials

Contact Info

Product

Resources

About