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New Insights into Metal–Insulator Transitions

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Materials Physics".

Deadline for manuscript submissions: closed (20 February 2024) | Viewed by 2425

Special Issue Editors


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Guest Editor
Department of Physics, Faculty of Science, University of Zagreb, Bijenicka Cesta 32, HR-10000 Zagreb, Croatia
Interests: condensed matter physics; correlated electron systems; metal–insulator transition; organic conductors; magnetotransport properties; quasi-one-dimensional cuprates; metallic glasses; half-metallic Heusler alloys; manganites

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Guest Editor
Institute of Physics, Bijenicka Cesta 46, HR-10000 Zagreb, Croatia
Interests: condensed matter physics; correlated electron systems; metal–insulator transition; spin and charge density waves; high-temperature superconductivity; quantum critical phenomena; magnetotransport properties; thermodynamic properties; organic conductors; manganites; cuprates; iron chalcogenides

Special Issue Information

Dear Colleagues,

Metal–insulator transitions (MITs) are one of the most important phenomena in condensed-matter physics. They connect two opposite boundaries: the metallic, where elementary excitations are single particles of a fermionic nature, and insulating, where elementary excitations are collective of a bosonic nature. Near the transition, both types of excitations coexist, which greatly complicates the problem from the theoretical side; thus, it is not surprising that its understanding is still incomplete, even after over 70 years of intensive research. There are various mechanisms that drive MITs through the localization of conducting electrons, most common ones being the Mott–Hubbard (caused by an electron–electron correlation), Anderson (caused by a disorder) and Peierls (caused by electron–phonon interactions) mechanisms. Some novel insights in these phenomena investigated the interplay between different mechanisms, and an especially interesting one is the complex theory of the Mott–Anderson localization, where both electron correlation and disorder cause electron localization. Additionally, interesting is the influence of electron localization on the magnetic degrees of freedom and the connection with spin liquids.

MITs have been observed in a variety of materials, with various exotic insulating ground states, including different charge and spin orderings, density waves, Mott insulators, etc. Additionally, interesting is the conducting side of MITs, where deviations from conventional Fermi liquid are often found. The transition between different states can be driven by a change in temperature, pressure, magnetic field, chemical substitution or doping. One of the most intriguing phenomena is colossal magnetoresistance (CMR), observed in manganites, where resistivity changes by several orders of magnitude with the application of a magnetic field, something which is still not fully understood, but that has been attributed to nanoscale phase separation.

The aim of this Special Issue is to report on novel experimental and theoretical findings regarding MITs and related intriguing phenomena, with the potential possibly of ascertaining numerous novel questions and future directions.

Prof. Dr. Emil Tafra
Dr. Matija Čulo
Guest Editors

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. Materials is an international peer-reviewed open access semimonthly 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 2600 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

  • metal–insulator transition
  • correlated electron systems
  • Mott localization
  • Anderson localization
  • Hubbard model
  • hopping conductivity
  • transport properties
  • dielectric properties
  • magnetic properties
  • optical properties
  • quantum spin liquids
  • charge order
  • organic conductors
  • manganites
  • cuprates

Published Papers (2 papers)

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Research

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12 pages, 3387 KiB  
Article
Negative Magnetoresistance in Hopping Regime of Lightly Doped Thermoelectric SnSe
by Marija Zorić, Naveen Singh Dhami, Kristian Bader, Peter Gille, Ana Smontara and Petar Popčević
Materials 2023, 16(7), 2863; https://doi.org/10.3390/ma16072863 - 04 Apr 2023
Cited by 1 | Viewed by 1378
Abstract
Semiconducting SnSe, an analog of black phosphorus, recently attracted great scientific interest due to a disputed report of a large thermoelectric figure of merit, which has not been reproduced subsequently. Here we concentrate on the low-temperature ground state. To gain a better understanding [...] Read more.
Semiconducting SnSe, an analog of black phosphorus, recently attracted great scientific interest due to a disputed report of a large thermoelectric figure of merit, which has not been reproduced subsequently. Here we concentrate on the low-temperature ground state. To gain a better understanding of the system, we present magneto-transport properties in high-quality single crystals of as-grown, lightly doped SnSe down to liquid helium temperatures. We show that SnSe behaves as a p-type doped semiconductor in the vicinity of a metal-insulator transition. Electronic transport at the lowest temperatures is dominated by the hopping mechanism. Negative magnetoresistance at low fields is well described by antilocalization, while positive magnetoresistance at higher fields is consistent with the shrinkage of localized impurity wavefunctions. At higher temperatures, a dilute metallic regime is realized where elusive T2 and B2 resistivity dependence is observed, posing a challenge to theoretical comprehension of the underlying physical mechanism. Full article
(This article belongs to the Special Issue New Insights into Metal–Insulator Transitions)
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Review

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23 pages, 1856 KiB  
Review
Charge Transport in the Presence of Correlations and Disorder: Organic Conductors and Manganites
by Emil Tafra, Mario Basletić, Tomislav Ivek, Marko Kuveždić, Nikolina Novosel, Silvia Tomić, Bojana Korin-Hamzić and Matija Čulo
Materials 2024, 17(7), 1524; https://doi.org/10.3390/ma17071524 - 27 Mar 2024
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Abstract
One of the most fascinating aspects of condensed matter is its ability to conduct electricity, which is particularly pronounced in conventional metals such as copper or silver. Such behavior stems from a strong tendency of valence electrons to delocalize in a periodic potential [...] Read more.
One of the most fascinating aspects of condensed matter is its ability to conduct electricity, which is particularly pronounced in conventional metals such as copper or silver. Such behavior stems from a strong tendency of valence electrons to delocalize in a periodic potential created by ions in the crystal lattice of a given material. In many advanced materials, however, this basic delocalization process of the valence electrons competes with various processes that tend to localize these very same valence electrons, thus driving the insulating behavior. The two such most important processes are the Mott localization, driven by strong correlation effects among the valence electrons, and the Anderson localization, driven by the interaction of the valence electrons with a strong disorder potential. These two localization processes are almost exclusively considered separately from both an experimental and a theoretical standpoint. Here, we offer an overview of our long-standing research on selected organic conductors and manganites, that clearly show the presence of both these localization processes. We discuss these results within existing theories of Mott–Anderson localization and argue that such behavior could be a common feature of many advanced materials. Full article
(This article belongs to the Special Issue New Insights into Metal–Insulator Transitions)
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