Composite fermions in quantum hall systems near ν=1/2

Author(s):  
Peter Wölfle
2012 ◽  
Vol 26 (23) ◽  
pp. 1230011 ◽  
Author(s):  
JANUSZ JACAK ◽  
RYSZARD GONCZAREK ◽  
LUCJAN JACAK ◽  
IRENEUSZ JÓŹWIAK

The topological explanation of the origin of Laughlin correlations in 2D charged systems under strong magnetic fields is formulated. Formal, self-consistent mathematical model of originally identified cyclotron braid subgroups is given in order to fully describe fundamentals of fractional quantum Hall effect, retrieve Laughlin correlations and point physical conditions which stand behind mysterious composite fermion structure. The new complete implementation of composite fermion basing on the first principles, without involving any artificial constructions (with flux-tubes or vortices) supply an explanation of previous models of composite fermions. Presented approach can lead to some corrections of numerical results in energy minimizations made within the traditional formulation of composite fermion model. Authors also identify the relations of FQHE in cyclotron braid terms within newly developing area of topological insulators and optical lattices. The prerequisites needed for formation of the fractional state are identified beyond the traditionally assumed factors, like the flat band condition and the interaction presence. The role of high mobility of carriers is highlighted in agreement with the experimental observations. Description, in terms of cyclotron braid subgroups, of the nature of yet unexplained novel experiments in Hall 2D systems including graphene is provided as well.


2002 ◽  
Vol 16 (20n22) ◽  
pp. 2956-2956
Author(s):  
A. STERN

In this talk I will discuss quantum interference phenomena of composite fermions in quantum Hall systems. In particular, I will focus on huge mesoscopic fluctuations of non-linear response and of Coulomb drag in single and bi-layer systems. Finally, I will give a simple physical picture of dephasing (de-coherence) of composite fermions, with simple expressions for their coherence length. Most of the talk will be based on work done in collaboration with I. Aleiner and B. Narozhny (Stony Brook).


2007 ◽  
Vol 21 (08n09) ◽  
pp. 1209-1218 ◽  
Author(s):  
YANN GALLAIS ◽  
THOMAS H. KIRSCHENMANN ◽  
JUN YAN ◽  
ARON PINCZUK ◽  
LOREN N. PFEIFFER ◽  
...  

Collective spin excitations in quantum Hall systems are studied via inelastic light scattering. In the fractional quantum Hall effect regime, composite fermion spin excitations are observed in the range 1/3< ν <2/5. They reveal a transition from free to strongly interacting composite fermions. At ν=1, a shift of the spin-wave energy at finite wavevector from the bare Zeeman energy is observed. It allows us to evaluate the spin-stiffness of the quantum Hall ferromagnet.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Nicodemos Varnava ◽  
Justin H. Wilson ◽  
J. H. Pixley ◽  
David Vanderbilt

AbstractEngineering and manipulation of unidirectional channels has been achieved in quantum Hall systems, leading to the construction of electron interferometers and proposals for low-power electronics and quantum information science applications. However, to fully control the mixing and interference of edge-state wave functions, one needs stable and tunable junctions. Encouraged by recent material candidates, here we propose to achieve this using an antiferromagnetic topological insulator that supports two distinct types of gapless unidirectional channels, one from antiferromagnetic domain walls and the other from single-height steps. Their distinct geometric nature allows them to intersect robustly to form quantum point junctions, which then enables their control by magnetic and electrostatic local probes. We show how the existence of stable and tunable junctions, the intrinsic magnetism and the potential for higher-temperature performance make antiferromagnetic topological insulators a promising platform for electron quantum optics and microelectronic applications.


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