Related Experiment Video
Updated: May 27, 2026
10:36
Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials
Published on: January 21, 2016
Dirac electrons of a split-gate Hall bar
P S Park1, S C Kim, S-R Eric Yang
1Physics Department, Korea University, Seoul 136-713, Korea.
Journal of Nanoscience and Nanotechnology
|November 30, 2011
Summary
Klein tunneling of Dirac electrons in graphene exhibits unique properties, showing complete transmission and significant electron density under barriers, even in a magnetic field. This suggests potential for STM detection and reveals deviations from semiclassical drift velocity predictions.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Mechanics
Background:
- Klein tunneling is a phenomenon where relativistic particles (like Dirac electrons in graphene) can tunnel through potential barriers with perfect transmission.
- Graphene's unique electronic properties, including the presence of Dirac cones, make it an ideal system for studying quantum transport phenomena.
- Split-gate Hall bar systems provide a tunable platform to investigate electron behavior under controlled potential barriers.
Purpose of the Study:
- To investigate the unusual properties of Klein tunneling in graphene within a split-gate Hall bar system with abrupt and flat potential barriers.
- To explore the strength of Klein tunneling and the electron density present under the barrier.
- To examine the behavior of electron wavefunctions and drift velocity in the presence of these barriers.
Main Methods:
- Theoretical study of Klein tunneling using Dirac electron models.
- Analysis of probability wavefunctions for electrons interacting with potential barriers.
- Investigation of electron drift velocity across potential barriers.
Main Results:
- Demonstrated strong Klein tunneling of Dirac electrons in the graphene system, with significant electron density observed under the barrier.
- Found that for large angular momenta, electron wavefunctions are identical to those without a barrier, indicating complete Klein tunneling.
- Observed a significant deviation from semiclassical results for electron drift velocity as the wavefunction center traverses the barrier.
Conclusions:
- Klein tunneling in this graphene system exhibits unique characteristics, including complete transmission and the presence of electron density under barriers, even in a magnetic field.
- The findings suggest that Scanning Tunneling Microscopy (STM) could be employed to detect the electron density under the barrier.
- The study highlights a departure from semiclassical predictions regarding electron drift velocity in the context of quantum tunneling.
Related Concept Videos
01:30The Hall Effect
Edwin H. Hall, in the year 1879, devised an experiment that could be used to identify the polarity of the predominant charge carriers in a conducting material. From a historical perspective, this experiment was the first to demonstrate that the charge carriers in most metals are negative.
01:22Semiconductors
There is variation in the electrical conductivity of materials - metals, semiconductors, and insulators that are showcased with the help of the energy band diagrams.
Metals such as copper (Cu), zinc (Zn), or lead (Pb) have low resistivity and feature conduction bands that are either not fully occupied or overlap with the valence band, making a bandgap non-existent. This allows electrons in the highest energy levels of the valence band to easily transition to the conduction band upon gaining...
Metals such as copper (Cu), zinc (Zn), or lead (Pb) have low resistivity and feature conduction bands that are either not fully occupied or overlap with the valence band, making a bandgap non-existent. This allows electrons in the highest energy levels of the valence band to easily transition to the conduction band upon gaining...
01:27Schottky Barrier Diode
Schottky barrier diodes are specialized semiconductor devices characterized by their unique construction. This construction involves combining a metal layer with a moderately doped n-type semiconductor material. This combination leads to the formation of a Schottky barrier, a pivotal element that defines the diode's operational characteristics. The core functionality of Schottky barrier diodes is their capacity to allow current to flow in only one direction due to their distinctive...
01:24Metal-Semiconductor Junctions
The contact of metal and semiconductor can lead to the formation of a junction with either Schottky or Ohmic behavior.
Schottky Barriers
Schottky barriers arise when a metal with a work function (Φm) contacts a semiconductor with a different work function (Φs). Initially, electrons transfer until the Fermi levels of the metal and semiconductor align at equilibrium. For instance, if Φm > Φs, the semiconductor Fermi level is higher than the metal's before contact. The semiconductor's...
Schottky Barriers
Schottky barriers arise when a metal with a work function (Φm) contacts a semiconductor with a different work function (Φs). Initially, electrons transfer until the Fermi levels of the metal and semiconductor align at equilibrium. For instance, if Φm > Φs, the semiconductor Fermi level is higher than the metal's before contact. The semiconductor's...
02:42Valence Bond Theory
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
01:12Fermi Level Dynamics
The vacuum level denotes the energy threshold required for an electron to escape from a material surface. It is usually positioned above the conduction band of a semiconductor and acts as a benchmark for comparing electron energies within various materials.
Electron affinity in semiconductors refers to the energy gap between the minimum of its conduction band and the vacuum level and it is a critical parameter in determining how easily a semiconductor can accept additional electrons.
The work...
Electron affinity in semiconductors refers to the energy gap between the minimum of its conduction band and the vacuum level and it is a critical parameter in determining how easily a semiconductor can accept additional electrons.
The work...