Neutron Scattering and Symmetry in Condensed Matter Physics

A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Physics".

Deadline for manuscript submissions: 31 March 2024 | Viewed by 3576

Special Issue Editor

Canadian Nuclear Laboratories, Chalk River, ON, Canada
Interests: condensed matter physics; superconductivity and magnetism; neutron scattering; nuclear magnetic resonance; scientific instrumentation; sample preparation and characterization

Special Issue Information

As condensed matter physicists, we think of crystals as beautifully ‘symmetric’ objects with periodic properties in space and are familiar with the translational and rotational symmetries of their lattices. In general, in physics, when we speak of symmetry, we refer to ‘the property of remaining invariant under certain mathematical transformation’ of, for example, the sign of electric charge, parity, direction of time flow, or orientation in space. Such mathematical transformations often also help with simplification of numerical calculations of physical laws. Symmetry concepts, however, offer more than just mathematical methodologies and simplified calculations. The importance of symmetry in condensed matter stems from the fact that there is an intimate connection between the symmetry of the Hamiltonian that describes a system and its properties (energy levels and their degeneracy). Since it is completely independent from the exact form of the Hamiltonian, the symmetry of the system imposes restrictions (selection rules for transitions between different states) on the possible solutions, and it is possible to determine solutions entirely by symmetry arguments. The symmetry properties of a physical system can provide powerful insight into its nature and offer predictions about the values of its measurable physical quantities. For example, one can determine whether a specific property is allowed under certain symmetry conditions and degrees of freedom required to describe it, entirely through symmetry arguments. Furthermore, from any observed regularities in measured quantities, one can trace back the symmetry of a system. Physical systems can thus be classified based on their symmetry. Such classification of physical systems, naturally, then links very different physical systems but with similar symmetry (even bridging classical and quantum physics systems).

Symmetry concepts also play an important role in the study of phase transitions. For example, a paramagnetic to ferromagnetic second-order phase transition involves a change in symmetry: the magnetization (order parameter) goes from zero value in the high-symmetry phase to a nonzero value in the low-symmetry phase. For phase transitions that are described by Landau phenomenological theory, a generalized phase diagram can be constructed again entirely based on symmetry arguments. Symmetry concepts are not only crucial for studying conventional phases of matter such as crystals, magnetic materials, and traditional superconductors; they are also key in topological insulators with a subtler interplay between symmetry and topology, resulting in a more complex phenomenology.

The second half of the last century witnessed the development of many experimental techniques that have enabled scientists to make precise measurements of microscopic properties of condensed matter systems. One notable technique is neutron scattering, revealing information about the sample that is often not attainable through other techniques. The unique properties of neutrons are the reason neutron scattering is proven to be one of the most valuable probes in condensed matter physics. Neutrons interact with condensed matter systems in two ways: nuclear and magnetic. Since thermal neutrons have a wavelength which is much larger than the nuclear interaction range, their scattering is described by s-wave scattering and characterized by a scattering length parameter. Neutrons also have a magnetic moment. Thus, they interact magnetically with electrons’ spin or orbital moment. In a neutron scattering experiment, a beam of well-characterized neurons are incident onto the sample and are detected after they interact with it. The properties of detected neutrons (orientation, energy, spin state) are then used to infer the sample properties. Two distinct types of neutron experiments include: elastic, where static properties (lattice and magnetic structures) are revealed, and inelastic, where dynamical properties (phonons, spin-waves, and spin excitations) are determined. Since the original work of Clifford Shull at Oak Ridge National Lab and Bertram Brockhouse at Chalk Ricer Laboratories in the 1940s and 1950s, for which they received a joint Nobel Prize in Physics in 1994, there have been tremendous advances in all aspects of this technique, from sophisticated instruments and extreme sample environments, to data analysis and visualization. All these have led to significant contributions by neutron scattering in all emerging themes of condensed matter physics such as quantum materials, unconventional superconductors (cuprate, iron–arsenide, and heavy fermions), low-dimensional quantum magnets, and topological insulators. Many novel theoretical models and their predictions such as Haldane gap and topological skyrmions were validated and further advanced by neutron scattering experiments.

Here, we present a selection of neutron scattering articles that showcase the power of this technique and how the usage of symmetry-based methods for the analysis of the ensuing data has led to many gains in understanding the physical behavior of quantum materials.

Dr. Zahra Yamani
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Symmetry is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • symmetry
  • neutron scattering
  • condensed matter physics
  • magnetism
  • superconductivity
  • lattice structure
  • lattice vibrations
  • phonons
  • magnetization
  • magnetic order
  • spin excitations
  • crystal field effects

Published Papers (2 papers)

Order results
Result details
Select all
Export citation of selected articles as:

Research

12 pages, 944 KiB  
Article
Revealing the Symmetry of Materials through Neutron Diffraction
Symmetry 2022, 14(6), 1215; https://doi.org/10.3390/sym14061215 - 12 Jun 2022
Viewed by 1189
Abstract
Magnetic materials are used in many devices in everyday life. To control their properties, we must first understand how they are ordered. This can be accomplished through neutron diffraction measurements. However, in many cases, there are too many parameters to determine the structure [...] Read more.
Magnetic materials are used in many devices in everyday life. To control their properties, we must first understand how they are ordered. This can be accomplished through neutron diffraction measurements. However, in many cases, there are too many parameters to determine the structure uniquely. Fortunately, symmetry can greatly constrain the number of parameters. Symmetry can also allow us to determine which physical properties are possible. In this review, I discuss the role of symmetry in magnetic structure determination using neutron diffraction. In this review, I will discuss both representational analysis as well as the magnetic superspace formalism. I will also discuss where the magnetic structure has been critical to understanding the fundamental science of the problem. Full article
(This article belongs to the Special Issue Neutron Scattering and Symmetry in Condensed Matter Physics)
Show Figures

Figure 1

12 pages, 2568 KiB  
Article
Magnetic Structure of Inorganic–Organic Hybrid (C6H5CH2CH2NH3)2MnCl4 Using Magnetic Space Group Concept
Symmetry 2020, 12(12), 1980; https://doi.org/10.3390/sym12121980 - 30 Nov 2020
Cited by 2 | Viewed by 1742
Abstract
Previously, we reported that inorganic–organic hybrid (C6H5CH2CH2NH3)2MnCl4 (Mn-PEA) is antiferromagnetic below 44 K by using magnetic susceptibility and neutron diffraction measurements. Generally, when an antiferromagnetic system is investigated by the [...] Read more.
Previously, we reported that inorganic–organic hybrid (C6H5CH2CH2NH3)2MnCl4 (Mn-PEA) is antiferromagnetic below 44 K by using magnetic susceptibility and neutron diffraction measurements. Generally, when an antiferromagnetic system is investigated by the neutron diffraction method, half-integer forbidden peaks, which indicate an enlargement of the magnetic cell compared to the chemical cell, should be present. However, in the case of the title compound, integer forbidden peaks are observed, suggesting that the size of the magnetic cell is the same as that of the chemical cell. This phenomenon was until now only theoretically predicted. During our former study, using an irreducible representation method, we suggested that four spin arrangements could be possible candidates and a magnetic cell and chemical cell should coincide. Recently, a magnetic structure analysis employing a magnetic space group has been developed. To confirm our former result by the representation method, in this work we employed a magnetic space group concept, and from this analysis, we show that the magnetic cell must coincide with the nuclear cell because only the Black–White 1 group (equi-translation or same translation group) is possible. Full article
(This article belongs to the Special Issue Neutron Scattering and Symmetry in Condensed Matter Physics)
Show Figures

Figure 1

Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: A neutron scattering study of magnetic structure and crystal field splitting for Er3+ in ErNiAl4
Authors: G A Stewart; Z Yamani; G N Iles; R A Mole; W D Hutchison; J M Cadogan; D H Ryan
Affiliation: /
Abstract: The orthorhombic, intermetallic series RNiAl4 (R = rare earth) exhibits interesting magnetic behaviour [1-2], including the potential for low temperature, inverse, magnetic cooling [3]. Given that the RNiAl4 magnetism is associated solely with the R sub-lattice and is influenced strongly by the local crystal field (CF) interaction at the R-site, it is important that the CF interaction is characterised. Both thermal and cold neutron scattering techniques are used to investigate the magnetic structure and the CF transitions associated with the single Er3+ site in ErNiAl4.

Back to TopTop