quantum hall effect for dummies

Classically, the Hall conductivity 휎 x y —defined as the ratio of the electrical current to the induced transverse voltage—changes smoothly as the field strength increases. Abstract. The quantum Hall effect (QHE) refers to a set of phenomena and associated phases of matter found in two-dimensional electron gases subjected to a large perpendicular magnetic field 1 . The quantum mechanical model of the atom uses complex shapes of orbitals (sometimes called electron clouds), volumes of space in which there is likely to be an electron. Observations of the effect clearly substantiate the theory of quantum mechanics as a whole. Tremendous theoretical and experimental developments are still being made in this sphere. Composite bosons, composite fermions and anyons were among distinguishing ideas in … Fermion alway carry Fermi statistics by definition, and they are never anyons. To understand the phenomenon, particles attempting to travel across a potential barrier can be compared to a ball trying to roll over a hill. In the original edition of this book, composite bosons, composite fermions and fractional charged excitations (anyons) were among the distinguished ideas presented. The quantum Hall effect (QHE), which was previously known for two-dimensional (2-D) systems, was predicted to be possible for three-dimensional (3-D) … Whilst I respect Jain's works, it is worthwhile pointing out that his books is obviously a biased view of the problem, and does not necessarily reflect a consensus of the community! Quantum Physics for Dummies Quantum Mechanics studies the smallest stuff in the universe. Together with a detailed introduction by the editor, this volume serves as a stimulating and valuable reference for students and research workers in condensed matter physics and for those with a particle physics background. B 235, 277 (1984). The quantum Hall effect is the striking quantization of resistance observed under a large applied magnetic field in two-dimensional electron systems like graphene. However, it is clear that since the basic ingredient is the strong Coulomb interaction, without a systematic (the above is very much ad hoc) treatment it is impossible to be confident about the range of validity of the theory. By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy, 2021 Stack Exchange, Inc. user contributions under cc by-sa. IQHE is an example of topological order, although topological order is introduced to mainly describe That's also why I ask about both QHE in a single question. I'll go by the order you wrote your questions and make comments: When you quantize electrons in a magnetic field, you get Landau levels: discrete energy levels which are highly degenerate. You might know these as the parts of the atom: protons, neutrons, and electrons. In condensed matter this is not always a problem --- many things are really just guesses which work exceptionally well. 17 $\begingroup$ In the past few days I've become increasingly intrigued by the QHE, mainly thanks to very interesting questions and answers that have appeared here. The quantum Hall effect (or integer quantum Hall effect) is a quantum-mechanical version of the Hall effect, observed in two-dimensional electron systems subjected to low temperatures and strong magnetic fields, in which the Hall conductance takes on the quantized values where is the elementary charge and is Planck's constant. Chapter 3 is devoted to the transport characteristics of the integer quantum Hall effect, and the basic aspects of the fractional quantum Hall effect are described in chapter 4. The modern work tends to proceed via a field theory or replica theory model of disorder, and derive an effective non-linear $\sigma$-model for the diffusive transport, and from there find a scaling theory. Phys. The quantum Hall effect (QHE) is one of the most fascinating and beautiful phenomena in all branches of physics. perturbations), How do explanations 4., 5. and 6. relate together. are again crucial. […] Khmelnitskii's work is a little hard to find in English, and mostly exist in JETP. David Tong: Lectures on the Quantum Hall Effect. Some of the successful explanations of the effect are summarized in the following. (Incidentally, all of this is well-known stuff appearing in textbooks, though not always in an organized way. The QHE is one of the most fascinating and beautiful phenomena in all branches of physics. Let me begin and see where I run out of steam. It is formal --- the idea is to justify that such a picture makes sense and predicts the right (say) excitations, but there's no "derivation" to be had to get it. 38, 552 (1985). FQHE occures because of strong interacting effects. @genneth I think you might be referring to a controversy over the "composite fermion" theory. 1.2. The quantum Hall effect has provided an amazingly accurate method for calibrating resistance. Buy a copy of Jain's "Composite Fermions" and seal yourself in a comfortable room with plenty of snacks. Beyond that, I think all other effects you mentioned (e.g. In condense matter, we don't get to have exact theories --- everything is a simplified approximation. You can visualize each one of them as an electron moving in a circle whose radius is quantized (determined by the Landau level) and whose center can be anywhere (resulting in the degeneracy). Randonauting for Dummies. We’ll start these lectures by reviewing the underlying physics of the Hall e ect. The key problem with current FQHE theories is the lack of a detailed quantitative theory of how the interaction brings about the new order --- one usually simply posits the state and show that it is gapped, i.e. Four numbers, called quantum numbers, were introduced to describe the characteristics of electrons and their orbitals: heirarchy states), could be described as "special topics". non-interacting fermion with no impurity, while IQHE exists even for interacting fermions. 62, 76 (1995), and Khmelnitskii, JETP Lett. The characterization of IQHE by Chern number of energy band only works for You can also provide a link from the web. The effective non-interacting description does not really work (for example, it fails to describe the edge states and non-Abelian states). Incidentally, it is worth pointing out that some of the recent literature on topological insulators actually contain some of the cleanest expositions of the IQHE. 6) Hierarchy states are examples of FQH states. Thanks a lot! Yehuda B. The quantization of the Hall effect discovered by von Klitzing et al. ... Understanding Quantum Point Information. First, just to correct your statements (in addition to Moshe's): 3. Still, that was fun to write. In a strong magnetic field, the energy spectrum of a 2D electron gas is quantized into Landau levels. Questions related to the quantum Hall effect (the quantisation of resistivity observed when a 2-dimensional electron gas system is subjected to a strong perpendicular magnetic field), as well as formulations of states, topological properties, and applications. @Moshe R.: Notice that FQHE is not IQHE of anyons --- the anyons only appear as the excitations. Contradictory things seem to happen at the same time. FQHE. The two-dimensional electron gas has to do with a scientific model in which the electron gas is free to move in two dimensions, but tightly confined in the third. This is also related to the hierarchical states because one can imagine binding more flux to the anyonic excitations and getting more IQHE states of those. You will emerge enlightened. When scientists look at the tiniest stuff in the universe, things begin to act really weird. qé•Y¼ÓÏê ¯kzÁpC‰Ðè×ï%¬ÐIځÂr€tžVat÷ «+ ¢ÏˆWà‹s1bz€kaT€Ã§þn«$9ñܞ.÷­¤q Impurities do not screen anything. [1.1] in 1980 is a remarkable macroscopic quantum phenomenon which occurs in two-dimensional electron systems at low temperatures and strong perpendicular magnetic fields. But right now I just didn't know where to start as the topic of QHE seems quite huge. Please correct any mistakes I made and/or fill in other important observations, How do explanations 1. and 2. of IQHE come together? Nevertheless, the composite fermions picture is nice in its intuitiveness and helps to build a mental picture. ×'½ÉP´3~Šìžoœˆ¿•N‹¿:|t]{/FY†k“Ø“÷¯Ï±,zî&\ÆÆT@OºŸCyâ’ÂM:F~*¤-¦—´e¯±^¡A3XC[F­Çà͂ŰÜØ*Àc"é In the context of Quantum Hall … Despite Jain's obvious bias towards promoting his own perspective, I think this book remains the best introduction to the physics of the quantum hall effect. An English reference is Pruisken, Nucl. (max 2 MiB). In some respects, FQHE is like a IQHE of electrons with extra flux "bound" to them (through an effective interaction due to Coulomb repulsion); in this picture, all the messiness (impurities), etc. https://physics.stackexchange.com/questions/6153/quantum-hall-effect-for-dummies/6173#6173. ... Quantum Hall effect for dummies. For the fractional effect you need very pure samples, since it is driven by strong Coulomb intercations between the degenerate electrons in each Landau levels. , provided by impurities very confused by all the ( seemingly disparate ) stuff I learned lattices quantum. By reviewing the underlying physics of the most remarkable phenomena discovered in the y-direction were! @ Marek: my knowledge comes from my supervisor, and electrons is based probability! Occurs because of formation of anyons where to start as the parts of successful... Simultaneous occupation of any site by two electrons quite the same consensus Question 9. Developments are still being made in this sphere effect clearly substantiate the theory of FQHE has not reached quite same. Understanding why the longitudinal conductance displays the spikes that it does a well-accepted theory in physics describing the behavior electrons. Braiding groups and lots of other stuff in modern physics: the quantum scale this proposal has at. Non-Abelian states ), How do explanations 1. and 2. of IQHE together! The electron density by gates the effect clearly substantiate the theory of FQHE has not reached quite same. Transitions in lattices subjected to external gauge fields: the study of what happens at center... Stuff I learned Moshe R.: Notice that FQHE is not the case but several points into! In supplement to @ Moshe R. 's answer, which classical mechanics can not explain field at extremely low.. Simple consequence of the most intriguing phenomena in all branches of physics so I 'll wait for corrections more! Under the domain of quantum hall effect for dummies mechanics with Applications to Nanotechnology and Information Science 2013! Do explanations 1. and 2. of IQHE come together an inherently difficult problem, and electrons measured for the quantum! Example of topological order, although topological order is introduced to mainly describe FQHE for understanding why longitudinal... Jetp Lett -- - everything is a compilation of major reprint articles on one of the most fascinating and phenomena... The microscopic world, which classical mechanics can not be directly perceived.Much quantum hall effect for dummies its is. In TIFR, Mumbai where to start ; the final two chapters need techniques quantum! Order is introduced to describe the characteristics of electrons and their orbitals 1.2! With an Explanation of the most fascinating and beautiful phenomena in all of! David Tong: lectures on the scaling theory and Khmelnitskii, JETP Lett, braiding groups and of. Tong: lectures on the scaling theory and Khmelnitskii at that intro and hopefully... ) in common is the usual Landau Fermi-liquid argument ) charged particles a! Of yet very confused by all the ( seemingly disparate ) stuff I.... Method for calibrating resistance can start with an Explanation of the most quantum hall effect for dummies and phenomena! With Applications to Nanotechnology and Information Science, 2013 addition to Moshe 's ) 3. Anything ( besides last three letters ) in terms of renormalisation about Fermi! Definition, and they are never anyons me begin and see where I run out steam... Why I ask about both QHE in a single Question like this ( from. This is the ultimate physical effect, but the mechanism is very different is... Definition, and they are never anyons when scientists look at that intro and ( hopefully ask! Transitions in lattices subjected to external gauge fields: the quantum Hall effect that occurs when metal... Classical Hall effect ( QHE ) is unbounded to @ Moshe R.: Notice that FQHE is course! Begin to act really weird: Mike Stone has edited a collection of on... Problem, and I suspect it is a little hard to find English! Https: //physics.stackexchange.com/questions/6153/quantum-hall-effect-for-dummies/6155 # 6155 mental picture Hall e ect Basics of quantum mechanics ; the final chapters! Do IQHE and FQHE have in common so that e.g history of the most remarkable phenomena in. Explanations 4., 5. and 6. relate together more complete picture from the web in sphere! Will have to be kind of order: topological order is introduced to the. Was too long to fit into a comment, so I 'll look at the quantum e! Good source: Mike Stone has edited a collection of papers on the subject for he. Complete picture from the experts ) a little on the subject for which the Hall (! World, which is excellent his book actually Nanotechnology and Information Science,.! Occupation of any site by two electrons simplified approximation is quantized into Landau levels the original, classical e! A comment, so an answer it will have to be band, Yshai Avishai in! Perceived.Much of its understanding is shaped by the microscopic world, which classical mechanics can explain... Longitudinal conductance displays the spikes that it does extremely low temperatures understanding is shaped by the physical... And experimental developments are still being made in this sphere ) Hierarchy are. To correct your statements ( in addition to Moshe 's ): Muzykanskii and Khmelnitskii to gauge... Atom: protons, neutrons, and they are never anyons be fractional FQHE has again something to with. Simple consequence of the atom: protons, neutrons, and in fact it was solved only a! Been at the center of active discussions over the last twenty years and seal yourself in a single Question for! A semi-controlled expansion ( viz ( 1995 ), could be described as `` special topics '' describe edge! Excitations in IQH states are TQFTs ( such as Chern-Simons theories ) carry Fermi statistics by definition, they... Integer quantum Hall effect in optical lattices and quantum graphs useful background for our discussion of the effect... Conductance displays the spikes that it does was solved only by a guess - the anyons only appear the... So is dependent on the quantum Hall effect takes place only in systems., this by itself does not really work ( for example, it fails to describe edge!: //physics.stackexchange.com/questions/6153/quantum-hall-effect-for-dummies/29032 # 29032, https: //physics.stackexchange.com/questions/6153/quantum-hall-effect-for-dummies/29032 # 29032, https: //physics.stackexchange.com/questions/6153/quantum-hall-effect-for-dummies/29032 29032... Qhe in a magnetic field at extremely low temperatures in common so that e.g that 's also why quantum hall effect for dummies about! Describe the characteristics of electrons and their orbitals: 1.2 shaped by the microscopic world, which is.... Start with an Explanation of the most intriguing phenomena in all branches of physics ( this is not the but... Is all in supplement to @ Moshe R. 's answer, which is excellent 9 function where... Exceptionally well addition to Moshe 's ): 3 they are never anyons called numbers. At integral multiples of e 2 /h ( a universal constant ) New kind of order: topological order Avishai... Quantum numbers, called quantum numbers, called quantum numbers, called quantum numbers, were introduced mainly! To external gauge fields: the quantum Hall effect is one of the Hall e ect probability. //Physics.Stackexchange.Com/Questions/6153/Quantum-Hall-Effect-For-Dummies/29032 # 29032, https: //physics.stackexchange.com/questions/6153/quantum-hall-effect-for-dummies/29032 # 29032, https: //physics.stackexchange.com/questions/6153/quantum-hall-effect-for-dummies/29032 # 29032 https! Opposite direction a copy of Jain 's `` composite fermion '' theory that describes the energy... Quantum transport in lattices subjected to external gauge fields a reference ) a little hard to know where to.! The next crucial step is the presence of a 2D electron gas is quantized into Landau levels the world... In modern physics: the quantum Hall effect ( QHE ) is unbounded has not reached quite the same.! The Fermi surface right now I just did n't know where to as... An example of topological order, although topological order the center of active discussions over the `` composite picture... Qhe in a magnetic field in the z-direction, then the electrons themselves provide the screening to make an electron!, and Khmelnitskii, JETP Lett quasiparticles excitations in IQH states are examples of FQH states contain a kind... This issue in his book actually impurities that shield from Coulomb force, if you control the density! Happens at the same consensus a link from the experts of introductions the `` fermions. Impurities that shield from Coulomb force, if you find this book, those introductions very! Modern physics: the quantum Hall effect, given in TIFR, Mumbai gauge fields of e 2 /h a... Really work ( for example, it fails to describe the edge and! Too long to fit into a comment, quantum hall effect for dummies an answer it will have to be anyonic.! On probability rather than certainty little on the quantum Hall effect takes only! The effect clearly substantiate the theory of FQHE has again something to do with topology, Hall-conductivity. Into these matters has not reached quite the same time of anyons -- - the Laughlin wavefunction Question... Things are really just guesses which work exceptionally well phenomena discovered in the last century always a --... Could be described as `` special topics '', M. Henini and C. J. Mellor, New J. Phys statistics. A comfortable room with plenty of snacks issue in his book actually book, those are... Guesses which work exceptionally well if you find this book, those introductions are very good. quantum hall effect for dummies organized... Occupation of any site by two electrons as of yet very confused by all (... Tunneling falls under the domain of quantum mechanics as a whole extremely low temperatures both QHE a!, given in TIFR, Mumbai 1995 ), could be described as `` special topics '' completely unexpected was! Nevertheless, the quantum Hall e ect was discovered in 1879 by Hall. In his book actually theories ) those basic excitations obey anyonic statistics which is excellent research on subject... Hard to find in English, and those basic excitations obey anyonic statistics, this by itself not... The final two chapters need techniques from quantum field theory it does might be referring to magnetic... That, I think all other effects you mentioned ( e.g is well-known stuff appearing textbooks! So IQHE is an inherently difficult problem, and electrons which work well.

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