AWhat changed
Feldmann and colleagues studied a biased GaAs/AlGaAs superlattice with time-resolved degenerate four-wave mixing at about 5 K. They observed oscillations in the emitted optical signal whose period changed with the electric field and agreed with the Bloch period inferred from the Wannier–Stark ladder spacing. A two-band calculation with a fitted dephasing time reproduced the signal, supporting their interpretation as coherent Bloch oscillations.
Scientific scope
Feldmann and colleagues studied a biased GaAs/AlGaAs superlattice with time-resolved degenerate four-wave mixing at about 5 K. They observed oscillations in the emitted optical signal whose period changed with the electric field and agreed with the Bloch period inferred from the Wannier–Stark ladder spacing. A two-band calculation with a fitted dephasing time reproduced the signal, supporting their interpretation as coherent Bloch oscillations. The measured quantity is a time-integrated diffracted optical signal as a function of pulse delay, not a direct trajectory of an individual electron. The oscillations can also be described as quantum beats between Wannier–Stark transitions. The calculation neglects Coulomb effects, and increasing dephasing at higher fields was attributed to carrier escape as a probable explanation. Results concern the specified 5 K semiconductor structure and finite coherence, not persistent oscillation in arbitrary bulk solids. Bloch theory and prior theoretical and experimental Wannier–Stark work retain their separate credit.
Evidence
The linked original works support the scoped statement and contribution attribution. WRS has not independently replayed experiments or reconstructed a full mathematical proof. The measured quantity is a time-integrated diffracted optical signal as a function of pulse delay, not a direct trajectory of an individual electron. The oscillations can also be described as quantum beats between Wannier–Stark transitions. The calculation neglects Coulomb effects, and increasing dephasing at higher fields was attributed to carrier escape as a probable explanation. Results concern the specified 5 K semiconductor structure and finite coherence, not persistent oscillation in arbitrary bulk solids. Bloch theory and prior theoretical and experimental Wannier–Stark work retain their separate credit.
Contributors
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