Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

AIP conference proceedings

Spin coherence of two-dimensional electron gas achieved via resonant excitation of trions and excitons

Evgeny A. Zhukov, Dmitri R. Yakovlev, M. Bayer, Михаил Михайлович Глазов, Eougenious L. Ivchenko, G. Karczewski, T. Wójtowicz, J. Kossut

Published Jan 1, 2007• 0 citations
Publisher

Abstract

Generation mechanisms of long‐lived spin coherence of two‐dimensional electron gas (2DEG) have been studied theoretically and experimentally, the latter by means of a picosecond pump‐probe Kerr rotation technique. CdTe/(Cd,Mg)Te quantum wells with a diluted two‐dimensional electron gas have been addressed. Strong Coulomb interaction between electrons and holes, which results in large binding energies of neutral and negatively charged excitons (trions), allows selective addressing of exciton and trion states with resonant optical excitation. Different scenarios of coherence generation have been analyzed, namely, direct trion photocreation, formation of trions from photogenerated excitons and electron‐exciton exchange scattering.

DOI
10.1063/1.2730409

Related papers

Spin Coherence of Holes in GaAs/AlGaAs Quantum Wells

M. Syperek, Dmitri R. Yakovlev, A. Greilich +4 more

Pump‐probe time‐resolved Kerr rotation technique has been used for experimental investigation of hole spin coherence in 15‐nm wide GaAs/AlGaAs quantum well structure in regime of diluted two‐dimensional hole gas. Due to the spectral width of 1.5 ps laser pulses which correspond to ∼1 meV, selective excitation of trion and exciton states has been performed. In the case of resonant excitation of exciton only the electron spin beats have been observed in the presence of magnetic field. In the case of resonant excitation of the positively charged exciton two component decay of time‐resolved Kerr rotation (TRKR) signal appeared. From the period of the quantum beat oscillation related to long decay component (up to 650 ps) of TRKR signal we obtained in‐plain hole g‐factor of ∼0.048±0.005.

AIP conference proceedings•Jan 1, 2007•5 citations

Optical control of electron spin coherence in CdTe/(Cd,Mg)Te quantum wells

Evgeny A. Zhukov, Dmitri R. Yakovlev, Михаил Михайлович Глазов +5 more

Optical control of the spin coherence of quantum well electrons by short laser pulses with circular or linear polarization is studied experimentally and theoretically. For that purpose the coherent electron spin dynamics in a $n$-doped CdTe/(Cd,Mg)Te quantum well structure was measured by time-resolved pump-probe Kerr rotation, using resonant excitation of the negatively charged exciton (trion) state. The amplitude and phase shifts of the electron spin beat signal in an external magnetic field, that are induced by laser control pulses, depend on the pump-control delay and polarization of the control relative to the pump pulse. Additive and nonadditive contributions to pump-induced signal due to the control are isolated experimentally. These contributions can be well described in the framework of a two-level model for the optical excitation of the resident electron to the trion.

arXiv:0912.2589•Physical Review B•Jun 16, 2010•30 citations

Spin Coherence of Holes in GaAs/(Al,Ga)As Quantum Wells

M. Syperek, Dmitri R. Yakovlev, A. Greilich +4 more

Carrier spin coherence in a p-doped GaAs/(Al,Ga)As quantum well with a diluted hole gas is studied by picosecond pump-probe Kerr rotation. For resonant optical excitation of the positively charged exciton the spin precession shows two types of oscillations: Electron spin beats decaying with the charged exciton radiative lifetime of 50 ps, and long-lived hole spin beats with dephasing times up to 650 ps, which decrease with increasing temperature, underlining the importance of hole localization. The mechanism of hole spin coherence generation is discussed.

arXiv:0704.0592•Physical Review Letters•Oct 29, 2007•83 citations

Exciton correlations within an electron gas

J. Berney

I report on the effect of a moderate excess electron population on nonlinearities in modulation-doped CdTe quantum wells. I show that the electron population does not qualitatively affect the nature of correlations between excitons. In this respect, I bring strong evidence of the existence of unbound and bound (stable) two-exciton states in the presence of electrons and charged excitons (trions). In time-resolved pump and probe experiment, they lead to the observation of electromagnetically induced transparency and optical Stark shift of the exciton resonance. Rabi flopping of excitons within a sea of electrons is also clearly evidenced through ac Stark splitting and gain without inversion. The quantum coherence is more robust to electron induced dephasing than what would have been expected. I demonstrate third and higher-order exciton correlations in the presence of electrons, which manifest, for increasing exciton densities, through the blue-shift of counter-polarized exciton resonance, the red-shift of the biexciton resonance and the exciton to biexciton crossover. I also evidence correlated behavior of excitons and trions under excitation which manifests itself by crossed trion-exciton effects. I observe a wealth of phenomena encompassing bleaching, crossed bleaching, induced-absorption and energy shifts of the resonances. Significant differences are found between the nonlinear optical effects induced by an exciton and a trion population. Electron scattering with electron and exciton is shown to strongly broaden the high energy tail of exciton and trion resonance lineshapes. Variations of electron density result in a clear modification of both resonance lineshapes. The dynamics of the formation of trions is also studied. I propose a two-channel mechanism for their formation; they are formed through bi- and tri-molecular processes. This implies that both negatively and positively charged excitons coexist in a quantum well, even in the absence of excess carriers. The model is applied to a time-resolved photoluminescence experiment performed on a very high quality InGaAs quantum well sample, in which the photoluminescence contributions at the energy of the trion, exciton and at the band edge can be clearly separated and traced over a broad range of times and densities. The unresolved discrepancy between the theoretical and experimental radiative decay time of the exciton in a doped semiconductor is explained.

•Nov 24, 2006•2 citations

Coherent spin dynamics of carriers in GaAs and CdTe semiconductor quantum wells

L. V. Fokina

Systematic investigation of the spin dephasing times in GaAs/(Al,Ga)As quantum wells and its depending on parameters like temperature, magnetic fields and doping will be shown in Chapter 3.In Chapter 4 are presented results of investigation of the nuclear spin systems in quantum well heterostructures.The chapter 5 presents the results of studying the carrier spin dynamics in a n-doped (In,Ga)As/GaAs quantum wells by time-resolved Faraday rotation and ellipticity techniques in the temperature range down to 430 mil-liKelvin.In Chapter 6 is devoted to experimental and theoretically studying of optical control of the spin coherence of quantum well electrons by short laser pulses with circular or linear polarization.For that purpose the coherent electron spin dynamics in a n-doped CdTe/(Cd,Mg)Te quantum well structure was measured by time-resolved pump-probe Kerr rotation, using resonant excitation of the negatively charged exciton (trion) state.on the eigenstates |s z ; ↑ and |s z ; ↓ yields the states themselves independent of time.Along the field axis (longitudinal direction) these quantum-mechanical spin states are thus stationary.Any loss of coherence is induced by coupling of those states with the environment.Applying the time-evolution operator on the spin states perpendicular

•Mar 24, 2010•0 citations

Coherent Coupling of Excitons and Trions in a Photoexcited CdTe/CdMgTe Quantum Well

Galan Moody, Ilya A. Akimov, Hebin Li +7 more

We present zero-, one-, and two-quantum two-dimensional coherent spectra of excitons and trions in a CdTe/(Cd,Mg)Te quantum well. The set of spectra provides a unique and comprehensive picture of the coherent nonlinear optical response. Distinct peaks in the spectra are manifestations of exciton-exciton and exciton-trion coherent coupling. Excellent agreement using density matrix calculations highlights the essential role of many-body effects on the coupling. Strong exciton-trion coherent interactions open up the possibility for novel conditional control schemes in coherent optoelectronics.

arXiv:1308.2165•Physical Review Letters•Mar 3, 2014•72 citations
Generation mechanisms of long‐lived spin coherence of two‐dimensional electron gas (2DEG) have been studied theoretically and experimentally, the latter by means of a picosecond pump‐probe Kerr rotation technique. CdTe/(Cd,Mg)Te quantum wells with a diluted two‐dimensional electron gas have been addressed. Strong Coulomb interaction between electrons and holes, which results in large binding energies of neutral and negatively charged excitons (trions), allows selective addressing of exciton and trion states with resonant optical excitation. Different scenarios of coherence generation have been analyzed, namely, direct trion photocreation, formation of trions from photogenerated excitons and electron‐exciton exchange scattering.
Pump‐probe time‐resolved Kerr rotation technique has been used for experimental investigation of hole spin coherence in 15‐nm wide GaAs/AlGaAs quantum well structure in regime of diluted two‐dimensional hole gas. Due to the spectral width of 1.5 ps laser pulses which correspond to ∼1 meV, selective excitation of trion and exciton states has been performed. In the case of resonant excitation of exciton only the electron spin beats have been observed in the presence of magnetic field. In the case of resonant excitation of the positively charged exciton two component decay of time‐resolved Kerr rotation (TRKR) signal appeared. From the period of the quantum beat oscillation related to long decay component (up to 650 ps) of TRKR signal we obtained in‐plain hole g‐factor of ∼0.048±0.005.
Optical control of the spin coherence of quantum well electrons by short laser pulses with circular or linear polarization is studied experimentally and theoretically. For that purpose the coherent electron spin dynamics in a nnn-doped CdTe/(Cd,Mg)Te quantum well structure was measured by time-resolved pump-probe Kerr rotation, using resonant excitation of the negatively charged exciton (trion) state. The amplitude and phase shifts of the electron spin beat signal in an external magnetic field, that are induced by laser control pulses, depend on the pump-control delay and polarization of the control relative to the pump pulse. Additive and nonadditive contributions to pump-induced signal due to the control are isolated experimentally. These contributions can be well described in the framework of a two-level model for the optical excitation of the resident electron to the trion.
Carrier spin coherence in a p-doped GaAs/(Al,Ga)As quantum well with a diluted hole gas is studied by picosecond pump-probe Kerr rotation. For resonant optical excitation of the positively charged exciton the spin precession shows two types of oscillations: Electron spin beats decaying with the charged exciton radiative lifetime of 50 ps, and long-lived hole spin beats with dephasing times up to 650 ps, which decrease with increasing temperature, underlining the importance of hole localization. The mechanism of hole spin coherence generation is discussed.
I report on the effect of a moderate excess electron population on nonlinearities in modulation-doped CdTe quantum wells. I show that the electron population does not qualitatively affect the nature of correlations between excitons. In this respect, I bring strong evidence of the existence of unbound and bound (stable) two-exciton states in the presence of electrons and charged excitons (trions). In time-resolved pump and probe experiment, they lead to the observation of electromagnetically induced transparency and optical Stark shift of the exciton resonance. Rabi flopping of excitons within a sea of electrons is also clearly evidenced through ac Stark splitting and gain without inversion. The quantum coherence is more robust to electron induced dephasing than what would have been expected. I demonstrate third and higher-order exciton correlations in the presence of electrons, which manifest, for increasing exciton densities, through the blue-shift of counter-polarized exciton resonance, the red-shift of the biexciton resonance and the exciton to biexciton crossover. I also evidence correlated behavior of excitons and trions under excitation which manifests itself by crossed trion-exciton effects. I observe a wealth of phenomena encompassing bleaching, crossed bleaching, induced-absorption and energy shifts of the resonances. Significant differences are found between the nonlinear optical effects induced by an exciton and a trion population. Electron scattering with electron and exciton is shown to strongly broaden the high energy tail of exciton and trion resonance lineshapes. Variations of electron density result in a clear modification of both resonance lineshapes. The dynamics of the formation of trions is also studied. I propose a two-channel mechanism for their formation; they are formed through bi- and tri-molecular processes. This implies that both negatively and positively charged excitons coexist in a quantum well, even in the absence of excess carriers. The model is applied to a time-resolved photoluminescence experiment performed on a very high quality InGaAs quantum well sample, in which the photoluminescence contributions at the energy of the trion, exciton and at the band edge can be clearly separated and traced over a broad range of times and densities. The unresolved discrepancy between the theoretical and experimental radiative decay time of the exciton in a doped semiconductor is explained.
Systematic investigation of the spin dephasing times in GaAs/(Al,Ga)As quantum wells and its depending on parameters like temperature, magnetic fields and doping will be shown in Chapter 3.In Chapter 4 are presented results of investigation of the nuclear spin systems in quantum well heterostructures.The chapter 5 presents the results of studying the carrier spin dynamics in a n-doped (In,Ga)As/GaAs quantum wells by time-resolved Faraday rotation and ellipticity techniques in the temperature range down to 430 mil-liKelvin.In Chapter 6 is devoted to experimental and theoretically studying of optical control of the spin coherence of quantum well electrons by short laser pulses with circular or linear polarization.For that purpose the coherent electron spin dynamics in a n-doped CdTe/(Cd,Mg)Te quantum well structure was measured by time-resolved pump-probe Kerr rotation, using resonant excitation of the negatively charged exciton (trion) state.on the eigenstates |s z ; ↑ and |s z ; ↓ yields the states themselves independent of time.Along the field axis (longitudinal direction) these quantum-mechanical spin states are thus stationary.Any loss of coherence is induced by coupling of those states with the environment.Applying the time-evolution operator on the spin states perpendicular
We present zero-, one-, and two-quantum two-dimensional coherent spectra of excitons and trions in a CdTe/(Cd,Mg)Te quantum well. The set of spectra provides a unique and comprehensive picture of the coherent nonlinear optical response. Distinct peaks in the spectra are manifestations of exciton-exciton and exciton-trion coherent coupling. Excellent agreement using density matrix calculations highlights the essential role of many-body effects on the coupling. Strong exciton-trion coherent interactions open up the possibility for novel conditional control schemes in coherent optoelectronics.