Related Experiment Video
Updated: Dec 22, 2025
11:33
All-electronic Nanosecond-resolved Scanning Tunneling Microscopy: Facilitating the Investigation of Single Dopant Charge Dynamics
Published on: January 19, 2018
10.1K
Mechanism of universal conductance fluctuations
V V Brazhkin1,2, I M Suslov1,2
1Institute for High Pressure Physics, 108840 Troitsk, Moscow, Russia.
Summary
Universal conductance fluctuations in thin wires are not random noise. Analysis reveals these magnetoresistance oscillations are a superposition of discrete frequencies, challenging previous interpretations.
Area of Science:
- Condensed Matter Physics
- Mesoscopic Physics
- Quantum Transport
Background:
- Universal conductance fluctuations (UCF) manifest as magnetoresistance oscillations in mesoscopic conductors.
- Previous interpretations suggested UCFs might be aperiodic or random, exhibiting white noise spectra.
Purpose of the Study:
- To re-evaluate the spectral characteristics of universal conductance fluctuations.
- To determine if UCFs are truly random or possess a discrete spectral nature.
Main Methods:
- Fourier analysis of magnetoresistance data from a classical experiment (Washburn and Webb).
- Comparison of observed spectra with theoretical models for random noise and discrete harmonic superpositions.
Main Results:
- The Fourier analysis revealed a purely discrete frequency spectrum for UCFs.
- The observed discrete spectrum closely resembles a discrete white noise spectrum, which shares properties with continuous white noise.
Conclusions:
- Universal conductance fluctuations arise from the superposition of incommensurate harmonics, not from random processes.
- The discrete nature of UCF spectra provides crucial insights into quantum transport phenomena in mesoscopic systems.
Related Concept Videos
01:17Theory of Metallic Conduction
1.7K
The conduction of free electrons inside a conductor is best described by quantum mechanics. However, a classical model makes predictions close to the results of quantum mechanics. It is called the theory of metallic conduction.
In this theory, Newton's second law of motion is used to determine the acceleration of an electron in the presence of an applied electric field. Then, its velocity is expressed via this acceleration.
An electron moves through the crystal, containing positive ions,...
In this theory, Newton's second law of motion is used to determine the acceleration of an electron in the presence of an applied electric field. Then, its velocity is expressed via this acceleration.
An electron moves through the crystal, containing positive ions,...
1.7K
01:25Boundary Conditions for Current Density
1.2K
Current density becomes discontinuous across an interface of materials with different electrical conductivities. The normal component of the current density is continuous across the boundary.
1.2K
01:13Electrical Conductivity
1.7K
In perfect conductors, the electric field inside is always zero due to the abundance of free electrons, which nullify any field by flowing. As a result, any residual charge resides on the surface.
In a practical conductor, an applied electric field may be sustained, causing a flow of electrons, which produce a current. The differential form of the current, the current density, is related to the electric field.
More generally, it is related to the force per unit charge, which involves the...
In a practical conductor, an applied electric field may be sustained, causing a flow of electrons, which produce a current. The differential form of the current, the current density, is related to the electric field.
More generally, it is related to the force per unit charge, which involves the...
1.7K
01:19Drift Velocity
5.2K
The high speed of electrical signals results from the fact that the force between charges acts rapidly at a distance. Thus, when a free charge is forced into a wire, the incoming charge pushes other charges ahead due to the repulsive force between like charges. These moving charges move the charges farther down the line. The density of charge in a system cannot easily be increased, so the signal is passed on rapidly. The resulting electrical shock wave moves through the system at nearly the...
5.2K
01:21Carrier Transport
838
The generation of electrical current in semiconductors is fundamentally driven by two mechanisms: drift and diffusion. These processes are essential for the functionality and performance of semiconductor-based devices.
Drift Current:
The drift of charge carriers is started by an external electric field (E). Charged particles, such as electrons and holes, experience an acceleration between collisions with lattice atoms. For electrons, this results in a drift velocity (vd) given by:
Drift Current:
The drift of charge carriers is started by an external electric field (E). Charged particles, such as electrons and holes, experience an acceleration between collisions with lattice atoms. For electrons, this results in a drift velocity (vd) given by:
838
01:22Lossy Lines and Overvoltages
297
Transmission-line series resistance and shunt conductance cause three primary effects: attenuation, distortion, and power losses.
Attenuation
When constant series resistance and shunt conductance are present, voltage and current equations are modified. The propagation constant indicates that voltage and current waves consist of both forward and backward traveling components. These waves attenuate as they propagate, with the attenuation factor related to the resistance and conductance. In a...
Attenuation
When constant series resistance and shunt conductance are present, voltage and current equations are modified. The propagation constant indicates that voltage and current waves consist of both forward and backward traveling components. These waves attenuate as they propagate, with the attenuation factor related to the resistance and conductance. In a...
297