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Related Concept Videos

Magnetic Fields01:27

Magnetic Fields

A moving charge or a current creates a magnetic field in the surrounding space, in addition to its electric field. The magnetic field exerts a force on any other moving charge or current that is present in the field. Like an electric field, the magnetic field is also a vector field. At any position, the direction of the magnetic field is defined as the direction in which the north pole of a compass needle points.
A magnetic field is defined by the force that a charged particle experiences...
Potential Due to a Magnetized Object01:24

Potential Due to a Magnetized Object

Magnetic dipoles in magnetic materials are aligned when placed under an external magnetic field. For paramagnets and ferromagnets, dipole alignment occurs in the direction of the magnetic field. However, the dipoles align opposite to the field in the case of diamagnets. This state of magnetic polarization due to the external field is called magnetization. Magnetization is defined as the dipole moment per unit volume. It plays a similar role to polarization in electrostatics.
The vector...
Magnetic Vector Potential01:15

Magnetic Vector Potential

In electrostatics, the electric field can be written as the negative gradient of the potential. In magnetostatics, the zero divergence of the magnetic field ensures that the magnetic field can be expressed as the curl of a vector potential. This potential is known as the magnetic vector potential.
Consider an ideal solenoid with n turns per unit length and radius R. If I is the current through the solenoid, the magnetic field inside the solenoid is expressed as the product of vacuum...
Magnetic Field due to Moving Charges01:23

Magnetic Field due to Moving Charges

A stationary charge creates and interacts with the electric field, while a moving charge creates a magnetic field.
Consider a point charge moving with a constant velocity. Like the electric field, the magnetic field at any point is directly proportional to the magnitude of the charge and inversely proportional to the square of the distance between the source point and the field point. However, unlike the electric field, the magnetic field is always perpendicular to the plane containing the line...
Atomic Nuclei: Nuclear Relaxation Processes01:23

Atomic Nuclei: Nuclear Relaxation Processes

In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis,  the precessing magnetic moments are randomly oriented around the z-axis. This...
Magnetic Field Due To A Thin Straight Wire01:27

Magnetic Field Due To A Thin Straight Wire

Consider an infinitely long straight wire carrying a current I. The magnetic field at point P at a distance a from the origin can be calculated using the Biot-Savart law.

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Related Experiment Video

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Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials
10:36

Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials

Published on: January 21, 2016

Magnetic quantum ratchet effect in graphene.

C Drexler1, S A Tarasenko, P Olbrich

  • 1Terahertz Center, University of Regensburg, 93040 Regensburg, Germany.

Nature Nanotechnology
|January 22, 2013
PubMed
Summary
This summary is machine-generated.

Researchers demonstrated an electronic ratchet in graphene, using magnetic fields and terahertz radiation to create directed current from asymmetric fluctuations. This magnetic quantum ratchet effect shows potential for other 2D materials.

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Nanofabrication of Gate-defined GaAs/AlGaAs Lateral Quantum Dots

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Fabrication of Gate-tunable Graphene Devices for Scanning Tunneling Microscopy Studies with Coulomb Impurities
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Nanofabrication of Gate-defined GaAs/AlGaAs Lateral Quantum Dots
15:47

Nanofabrication of Gate-defined GaAs/AlGaAs Lateral Quantum Dots

Published on: November 1, 2013

Area of Science:

  • Condensed Matter Physics
  • Materials Science
  • Quantum Mechanics

Background:

  • Periodically driven systems with spatial asymmetry can exhibit directed motion via fluctuations, known as the ratchet effect.
  • Graphene, typically symmetric, should not produce a directed current under periodic electric fields.
  • Loss of spatial symmetry in graphene, due to substrates or adatoms, can induce electronic ratchet motion.

Purpose of the Study:

  • To experimentally demonstrate an electronic ratchet effect in graphene layers.
  • To prove the underlying spatial asymmetry responsible for ratchet motion.
  • To investigate the role of magnetic fields and terahertz radiation in inducing and controlling this effect.

Main Methods:

  • Inducing orbital asymmetry in Dirac fermions using an in-plane magnetic field.
  • Applying periodic driving using terahertz radiation.
  • Experimental observation of ratchet transport in graphene.

Main Results:

  • Demonstrated an electronic ratchet in graphene, confirming spatial asymmetry.
  • Observed the transformation of AC power into DC current via a magnetic quantum ratchet.
  • Showcased the extraction of work from out-of-equilibrium electrons driven by undirected periodic forces.

Conclusions:

  • The study provides experimental evidence for structure inversion asymmetry in graphene.
  • The findings suggest that orbital effects and ratchet transport may be significant in other 2D materials like boron nitride and transition metal dichalcogenides.
  • This work highlights the potential of magnetic quantum ratchets for energy conversion in nanoscale systems.