Fractional Quantum Hall Effect

Definition

The fractional quantum Hall effect (FQHE) is a phenomenon observed in two-dimensional electron systems subjected to low temperatures and strong magnetic fields, where the Hall conductivity takes on quantized values that are fractional multiples of fundamental constants. This effect reveals the underlying quantum mechanical nature of electrons and their collective behavior, giving rise to unique excitations known as anyons, which play a crucial role in understanding topological phases of matter.

5 Must Know Facts For Your Next Test

1. The fractional quantum Hall effect was first observed experimentally in 1982 by Tsui, Störmer, and Gossard, leading to the Nobel Prize in Physics in 1998.
2. In FQHE, the filling factor, denoted as $ u$, determines the quantized values of Hall conductivity and can take on fractional values like 1/3 or 5/2.
3. The emergence of anyons in the fractional quantum Hall effect allows for exotic braiding statistics that can be utilized in topological quantum computing.
4. The FQHE challenges traditional concepts of charge and statistics, revealing how electron interactions can lead to new phases of matter.
5. It is theorized that the fractional quantum Hall effect is a manifestation of a deeper topological order present in two-dimensional systems under specific conditions.

Review Questions

• How does the fractional quantum Hall effect differ from the integer quantum Hall effect in terms of filling factors and underlying physics?
  • The main difference between the fractional and integer quantum Hall effects lies in their filling factors. While the integer quantum Hall effect occurs at integer values of the filling factor, leading to quantized Hall conductivity values that are integral multiples of fundamental constants, the fractional quantum Hall effect occurs at fractional filling factors. This distinction results from different underlying physics; FQHE arises due to strong electron correlations and collective behavior, giving rise to unique quasiparticles known as anyons that do not appear in the integer case.
• Discuss how anyons contribute to the understanding of the fractional quantum Hall effect and their significance in modern physics.
  • Anyons are crucial for understanding the fractional quantum Hall effect because they exhibit non-traditional statistics that differ from both bosons and fermions. These quasiparticles arise from the collective excitations of electrons in a two-dimensional system under strong magnetic fields. The unique properties of anyons, including their ability to exhibit braiding statistics, make them promising candidates for topological quantum computing, where information is stored using these robust states against local disturbances. This highlights not only their significance in condensed matter physics but also their potential applications in future technologies.
• Evaluate the implications of topological order in systems exhibiting the fractional quantum Hall effect and its impact on future technologies.
  • Topological order in systems showing the fractional quantum Hall effect fundamentally alters our understanding of phase transitions and states of matter. Unlike traditional orders based on local symmetry breaking, topological order characterizes states by global properties and their response to perturbations. This has profound implications for future technologies, particularly in quantum computing. The robustness of topological qubits against local noise presents a pathway for developing fault-tolerant quantum computers. As researchers continue to explore these connections, advancements in our understanding of topological phases could lead to breakthroughs in both fundamental physics and practical applications.

Related terms

Quantum Hall Effect: A phenomenon where the Hall resistance of a two-dimensional electron gas becomes quantized in integer multiples of fundamental constants when subjected to strong magnetic fields.

Anyons: Quasiparticles that arise in two-dimensional systems, exhibiting statistics that are neither fermionic nor bosonic, and are significant in the context of the fractional quantum Hall effect.

Topological Order: A type of order in quantum states that is characterized by global properties rather than local symmetries, playing a central role in understanding the fractional quantum Hall effect and anyon statistics.