Symmetry and Symmetry Breaking in Quantum Mechanics

A special issue of Symmetry (ISSN 2073-8994).

Deadline for manuscript submissions: closed (31 May 2017) | Viewed by 13589

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Aerospace Engineering School, International University of Rabat, Campus de l’UIR, Parc Technopolis, Rocade de Rabat-Salé, 11100-Sala Al Jadida - Maroc
Interests: condensed-matter physics theory; high-temperature superconductivity; quantum spin systems; quantum crtitcality; numerical modeling; rotating antiferromagnetism
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Special Issue Information

Dear Colleagues,

There is no doubt that symmetry plays one of the most important roles in physics. Symmetry breaking is also a very interesting and essential phenomenon in both condensed matter physics and high-energy physics. The recently-discovered Higgs boson is the most famous consequence of symmetry breaking. Things got even more interesting lately with the proposal of hidden order that could arise from some sort of hidden symmetry breaking, as proposed for the explanation of the pseudogap state of the high-TC cuprate materials. Additionally, the role of symmetry in topological phases of matter has recently gained a tremendous importance with the discovery of topological insulators for example. This Special Issue welcomes manuscripts from all areas of quantum physics where symmetry and/or symmetry breaking occur.

Prof. Dr. Mohamed Azzouz
Guest Editor

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Keywords

  • Group theory and symmetry
  • Spin liquids; disordered quantum states
  • Symmetry breaking; ordered states
  • Hidden order and hidden symmetry breaking
  • Symmetry in topological phases
  • Translation, parity, time reversal symmetries  
  • Gauge symmetries
  • Quantum criticality
  • Symmetry and spintronics

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Published Papers (3 papers)

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Research

241 KiB  
Article
Magnetic Transport in Spin Antiferromagnets for Spintronics Applications
by Mohamed Azzouz
Symmetry 2017, 9(10), 225; https://doi.org/10.3390/sym9100225 - 13 Oct 2017
Cited by 1 | Viewed by 3687
Abstract
Had magnetic monopoles been ubiquitous as electrons are, we would probably have had a different form of matter, and power plants based on currents of these magnetic charges would have been a familiar scene of modern technology. Magnetic dipoles do exist, however, and [...] Read more.
Had magnetic monopoles been ubiquitous as electrons are, we would probably have had a different form of matter, and power plants based on currents of these magnetic charges would have been a familiar scene of modern technology. Magnetic dipoles do exist, however, and in principle one could wonder if we can use them to generate magnetic currents. In the present work, we address the issue of generating magnetic currents and magnetic thermal currents in electrically-insulating low-dimensional Heisenberg antiferromagnets by invoking the (broken) electricity-magnetism duality symmetry. The ground state of these materials is a spin-liquid state that can be described well via the Jordan–Wigner fermions, which permit an easy definition of the magnetic particle and thermal currents. The magnetic and magnetic thermal conductivities are calculated in the present work using the bond–mean field theory. The spin-liquid states in these antiferromagnets are either gapless or gapped liquids of spinless fermions whose flow defines a current just as the one defined for electrons in a Fermi liquid. The driving force for the magnetic current is a magnetic field with a gradient along the magnetic conductor. We predict the generation of a magneto-motive force and realization of magnetic circuits using low-dimensional Heisenberg antiferromagnets. The present work is also about claiming that what the experiments in spintronics attempt to do is trying to treat the magnetic degrees of freedoms on the same footing as the electronic ones. Full article
(This article belongs to the Special Issue Symmetry and Symmetry Breaking in Quantum Mechanics)
321 KiB  
Article
Spatio-Temporal Symmetry—Point Groups with Time Translations
by Haricharan Padmanabhan, Maggie L. Kingsland, Jason M. Munro, Daniel B. Litvin and Venkatraman Gopalan
Symmetry 2017, 9(9), 187; https://doi.org/10.3390/sym9090187 - 8 Sep 2017
Cited by 5 | Viewed by 5888
Abstract
Spatial symmetries occur in combination with temporal symmetries in a wide range of physical systems in nature, including time-periodic quantum systems typically described by the Floquet formalism. In this context, groups formed by three-dimensional point group symmetry operations in combination with time translation [...] Read more.
Spatial symmetries occur in combination with temporal symmetries in a wide range of physical systems in nature, including time-periodic quantum systems typically described by the Floquet formalism. In this context, groups formed by three-dimensional point group symmetry operations in combination with time translation operations are discussed in this work. The derivation of these ’spatio-temporal’ groups from conventional point groups and their irreducible representations is outlined, followed by a complete listing. The groups are presented in a template similar to space group operations, and are visualized using a modified version of conventional stereographic projections. Simple examples of physical processes that simultaneously exhibit symmetry in space and time are identified and used to illustrate the application of spatio-temporal groups. Full article
(This article belongs to the Special Issue Symmetry and Symmetry Breaking in Quantum Mechanics)
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198 KiB  
Article
Quantum Correlations under Time Reversal and Incomplete Parity Transformations in the Presence of a Constant Magnetic Field
by Paolo De Gregorio, Sara Bonella and Lamberto Rondoni
Symmetry 2017, 9(7), 120; https://doi.org/10.3390/sym9070120 - 18 Jul 2017
Cited by 4 | Viewed by 3133
Abstract
We derive the quantum analogues of some recently discovered symmetry relations for time correlation functions in systems subject to a constant magnetic field. The symmetry relations deal with the effect of time reversal and do not require—as in the formulations of Casimir and [...] Read more.
We derive the quantum analogues of some recently discovered symmetry relations for time correlation functions in systems subject to a constant magnetic field. The symmetry relations deal with the effect of time reversal and do not require—as in the formulations of Casimir and Kubo—that the magnetic field be reversed. It has been anticipated that the same symmetry relations hold for quantum systems. Thus, here we explicitly construct the required symmetry transformations, acting upon the relevant quantum operators, which conserve the Hamiltonian of a system of many interacting spinless particles, under time reversal. Differently from the classical case, parity transformations always reverse the sign of both the coordinates and of the momenta, while time reversal only of the latter. By implementing time reversal in conjunction with ad hoc “incomplete” parity transformations (i.e., transformations that act upon only some of the spatial directions), it is nevertheless possible to achieve the construction of the quantum analogues of the classical maps. The proof that the mentioned symmetry relations apply straightforwardly to quantal time correlation functions is outlined. Full article
(This article belongs to the Special Issue Symmetry and Symmetry Breaking in Quantum Mechanics)
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