Anomalous Nonlinear Shot Noise at High Voltage Bias.

Area of Science:

• Condensed Matter Physics
• Quantum Transport
• Nanoscale Electronics

Background:

• Walter Schottky established that shot-noise power scales linearly with average current for uncorrelated electrons.
• This linear relationship is generally robust, even for correlated electrons, under specific conditions (zero temperature, no inelastic scattering).
• Investigating shot noise in nanoscale systems is crucial for understanding fundamental electron transport.

Purpose of the Study:

• To investigate the behavior of shot-noise power in single-atom point contacts under high bias conditions.
• To explore deviations from the expected linear relationship between noise power and current/voltage.
• To elucidate the underlying physical mechanisms responsible for observed nonlinearities.

Main Methods:

• Performed high-bias shot-noise measurements on single gold (Au) atom point contacts.
• Analyzed the relationship between noise power and applied voltage.
• Developed a theoretical model incorporating quantum interference effects.

Main Results:

• Observed highly nonlinear behavior in shot-noise power at high bias voltages.
• Demonstrated instances where shot noise decreased with increasing voltage.
• The results contradict the classical linear scaling predicted by Schottky.

Conclusions:

• Quantum interference of electron waves, influenced by scattering from defect sites, explains the observed nonlinear shot noise.
• The transmission probability of electrons becomes dependent on both energy and voltage due to these interference effects.
• This finding highlights the importance of quantum phenomena in nanoscale electronic transport and noise characteristics.