Related Experiment Video
Updated: Aug 13, 2026
05:39
Scalable Quantum Integrated Circuits on Superconducting Two-Dimensional Electron Gas Platform
Published on: August 2, 2019
Out-of-equilibrium Kondo effect in a mesoscopic device
S De Franceschi1, R Hanson, W G Van Der Wiel
1Department of NanoScience, DIMES, and ERATO Mesoscopic Correlation Project, Delft University of Technology, P.O. Box 5046, The Netherlands.
Physical Review Letters
|October 9, 2002
Summary
We observed a split Kondo resonance in a quantum dot system under bias voltage. A magnetic field selectively controls coupling, suppressing Kondo correlations at higher voltages.
Area of Science:
- Condensed Matter Physics
- Quantum Dot Physics
- Mesoscopic Systems
Background:
- The Kondo effect describes the interaction between localized magnetic moments and conduction electrons in metals.
- Understanding the Kondo effect in nonequilibrium regimes is crucial for quantum information processing and spintronics.
- Quantum dots offer a tunable platform to study fundamental condensed matter phenomena like the Kondo effect.
Purpose of the Study:
- To investigate the nonequilibrium Kondo effect in a quantum dot coupled to a narrow wire.
- To analyze the influence of bias voltage and magnetic field on Kondo resonance.
- To understand the suppression and control of Kondo correlations.
Main Methods:
- Utilizing a quantum dot laterally coupled to a narrow wire.
- Applying a finite bias voltage across the wire to induce nonequilibrium conditions.
- Employing a perpendicular magnetic field to control the coupling strength to different electronic reservoirs.
Main Results:
- A split Kondo resonance was observed under finite bias voltage, attributed to a double-step Fermi distribution.
- Kondo correlations were found to be strongly suppressed when the applied voltage exceeded the Kondo temperature.
- A perpendicular magnetic field of approximately 0.1 T selectively preserved the Kondo resonance associated with the strongly coupled reservoir.
Conclusions:
- The study demonstrates the tunability of Kondo correlations in a quantum dot system via bias voltage and magnetic field.
- Nonequilibrium conditions significantly alter Kondo resonance properties, offering new avenues for device control.
- Selective control over reservoir coupling provides a mechanism for manipulating quantum phenomena in mesoscopic systems.
Related Concept Videos
01:14Atomic Nuclei: Nuclear Spin State Population Distribution
Near absolute zero temperatures, in the presence of a magnetic field, the majority of nuclei prefer the lower energy spin-up state to the higher energy spin-down state. As temperatures increase, the energy from thermal collisions distributes the spins more equally between the two states. The Boltzmann distribution equation gives the ratio of the number of spins predicted in the spin −½ (N−) and spin +½ (N+) states.
01:23Atomic 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...
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...
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...
01:27Biasing of Metal-Semiconductor Junctions
Biasing metal-semiconductor junctions involves applying a voltage across the junction. Specifically, the metal is connected to a voltage source, while the semiconductor is grounded. This technique is essential for controlling the direction and magnitude of current flow in electronic devices, including diodes, transistors, and photovoltaic cells.
In Schottky junctions, where the semiconductor is n-type, applying a positive voltage to the metal relative to the semiconductor reduces its Fermi...
In Schottky junctions, where the semiconductor is n-type, applying a positive voltage to the metal relative to the semiconductor reduces its Fermi...
01:28Debye–Huckel–Onsager Conductance Equation
The Debye-Hückel-Onsager equation is a cornerstone of physical chemistry, providing a method to determine the molar conductance (Λm) and molar conductance at infinite dilution (Λ°m) for uni-univalent electrolytes.Uni-univalent electrolytes are electrolytes that dissociate in solution to produce one cation with a +1 charge and one anion with a –1 charge per formula unit.This equation addresses two crucial phenomena: the asymmetry effect and the electrophoretic effect. According to this equation,...