Sample interview questions: Can you explain the concept of quantum tunneling and its implications in solid-state physics?
Sample answer:
Quantum Tunneling:
Quantum tunneling is a phenomenon in which a particle can pass through a potential barrier even if it does not have enough energy to overcome it classically. This is possible because particles also have wave-like properties, and they can therefore tunnel through the barrier.
Implications in Solid-State Physics:
- Tunnel Diodes:
- Quantum tunneling is utilized in tunnel diodes, where a thin insulating layer separates two heavily doped semiconductor regions.
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When a small bias voltage is applied, electrons can tunnel through the barrier, resulting in a high current.
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Scanning Tunneling Microscopy (STM):
- STM employs quantum tunneling to image surfaces at the atomic level.
- A sharp metal tip is brought close to the surface, and a bias voltage is applied.
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Electrons can tunnel from the tip to the surface or vice versa, creating a current that is sensitive to the surface topography.
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Magnetic Tunnel Junctions (MTJs):
- MTJs consist of two ferromagnetic layers separated by a thin insulating layer.
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The relative magnetization of the layers determines the tunnel resistance, allowing for applications in magnetic sensors and memory devices.
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Superconductivity:
- Superconductivity is a state in which a material exhibits zero electrical resistance below a certain critical temperature.
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