SearcharxivSearch

arXiv · 1603.08625

Theory of the Integer and Fractional Quantum Hall Effects

Abstract

The present theory has investigated the FQHE without any quasi-particle. The electric field due to the Hall voltage is taken into consideration. We find the ground state where the electron configuration is uniquely determined so as to have the minimum classical Coulomb energy. Residual Coulomb interaction HI yields quantum transitions which satisfy the momentum conservation along the current direction. The number of Coulomb transitions from nearest electron pairs is dependent sensitively upon the fractional number of the filling factor. For example, the number u(2/3) of allowed transitions at nu=2/3 abruptly decreases when the filling factor nu deviates slightly from 2/3. The limiting value of the number is equal to half of u(2/3). The discontinuous behavior produces the valley structure in the energy spectrum. This mechanism produces the Hall plateaus at the specific filling factors nu=1/(2j+1), 2j /(2j+1), j/(2j+1), j/(2j-1) etc. and also at the non-standard filling factors nu=7/11, 4/11, 4/13, 5/13, 5/17, 6/17 etc. We have studied the pair energies of more distant electron pairs in Chapter 5. Thereby the small valley structure yields at nu=5/2, 7/2 and so on. The shapes of polarization curves depend mainly upon the numerator of the fractional filling factor in nu<1 because the spin polarization belongs to electrons only. There are many spin-arrangements with the same eigen-energy of HD. The Coulomb interaction HI yields quantum transitions among these degenerate ground states. The partial Hamiltonian has been diagonalized exactly. The eigen-states give the spin polarization versus magnetic field strength. The theoretical curves of the spin polarization are in good agreement with the experimental data as studied in Chapter 9. Thus the present theory has well explained the various phenomena of the FQHE.

Explore related subjects

Keep this discovery

BibTeXRIS

Shosuke Sasaki. 2016-03-29. Theory of the Integer and Fractional Quantum Hall Effects. https://arxiv.org/abs/1603.08625

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

Emergence of spin-orbit coupling among spin, atomic orbital, and Bloch dynamics in Janus double-transition-metal MXenes

We found a spin-orbit coupling to cause a simultaneous correlation among three degrees of freedom, the electronic spin, orbital, and Bloch dynamics in an investigation into the electronic structure of Janus double-transition-metal MXenes, Mo$_2$HfC$_2$OS and W$_2$HfC$_2$OS. In this paper, it is also revealed that the spin-orbit coupling causes a staggered spin configuration with a trigonal pattern around the $\Gamma$ point near the insulating gap. We developed a reduced Hamiltonian describing the electronic states and show that the spin-orbit coupling cannot be equated with conventional forms for a single electron in solids, LS, Rashba, and Dresselhaus couplings, even in the approximation under the low-energy and small wave number condition. Because of the intrinsic shape of the conduction band, a trigonally alternating spin-momentum locking emerges with the spin axis perpendicular to the layer plane. The theoretical analysis shows that these Janus materials can provide a platform for exploring the spin-related phenomena due to the trigonal spin-momentum locking other than Rashba and Dresselhaus types.

cond-mat.mes-hall

A substrate booster for P-type 2D ferromagnetic semiconductor

Spin transistors with its both charge and spin properties tuned via electrostatic gating are believed capable for widespread use, which however have proven challenging due to the extreme rareness of their physical base -- magnetic semiconductors. The latter are limited within very few systems including diluted magnetic semiconductors (DMS) and two-dimensional ferromagnetic semiconductors (2D-FMS), and known to suffer from inadequate gate-tunability of their electric and/or magnetic properties. Here, we show a substrate engineering paradigm by interfacing few-layered Cr$_{2}$Ge$_{2}$Te$_{6}$ (FL-CGT) with an antiferromagnetic insulator CrOCl. Owing to the subtle interfacial charge transfer couplings, CGT can be drastically turned from an ambipolar semiconductor into a high performance P-type semiconductor. When cooled below the Curie temperature, the ON-OFF ratio in such substrate-boosted FMS field-effect transistor (FET) reaches 10$^{5}$ with its coercive field $H_{c}$ of magnetic hysteresis loop tunable by a factor of more than 200$\%$, enabling {gate-assisted magnetic switching in the prototype semiconducting spin transistor architecture}. A crossover from critical power-law scaling to a dual power-law behaviour under heavy hole doping was further observed. Our findings {signify} an efficient interfacial charge transfer and electrically modulated magnetic anisotropy energy supported by calculations. This high performance P-type FMS-FET system suggests that active substrate-boosting paradigm might be a powerful path for the investigation of future gate-tunable spintronic devices.

cond-mat.mes-hall

In-plane magnetic field control of anomalous Hall response enabled by magnetic anisotropy engineering

Engineering magnetic anisotropy provides a powerful route to control magnetization orientation and unlock emerging functionalities in opto-spintronic and current-driven devices. Beyond its role in magnetization reversal, the effective anisotropy can strongly influence the magnetotransport response, offering an additional degree of freedom to tune new device functionalities. In this work, we report a magnetotransport study of a ferrimagnetic [Tb/Co]$_{\times 5}$ multilayer grown with a Tb thickness gradient, whose wedge-shaped tilts the uniaxial anisotropy axis slightly away from the film normal. Anomalous Hall resistivity measurements from 80 K to 300 K reveal a spin reorientation transition, while the angular dependence of the magnetotransport responses exposes the crucial role of the tilted anisotropy. A simplified macrospin model reproduces the full angular response across the transition and shows that the observed anomalous Hall effect when the in-plane magnetic field is applied originates from the tilt of the uniaxial anisotropy axis, which supplies a built-in symmetry-breaking mechanism, enabling in-plane field control over the out-of-plane anomalous Hall response, sign included. These findings establish tilted magnetic anisotropy as a promising route toward Hall effect-based sensor applications and highlight Tb/Co multilayers as a versatile platform for anisotropy-engineered spintronic devices.

cond-mat.mes-hall