Special Issue "Quantum Complex Matter 2020"

A special issue of Condensed Matter (ISSN 2410-3896). This special issue belongs to the section "Quantum Materials".

Deadline for manuscript submissions: closed (31 October 2020).

Special Issue Editor

Prof. Dr. Antonio Bianconi
E-Mail Website
Guest Editor
Rome International Center for Materials Science Superstripes (RICMASS), Via dei Sabelli 119A, 00185 Roma, Italy
Interests: synchrotron radiation research; protein fluctuations; active sites of metalloproteins; origin of life; selected molecules in prebiotic world; quantum phenomena in complex matter; quantum confinement; superstripes in complex matter; lattice complexity in transition metal oxides; high Tc superconductors; valence fluctuation materials
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Special Issue Information

Dear Colleagues,

This Special Issue will publish selected papers from the Quantum Complex Matter (QCM) 2020 conference, in joint collaboration with the QCM school, on 8–12 June 2020 in Frascati, Italy. You are warmly invited to contribute an article/review paper for possible publication in our Special Issue. Submissions will be rapidly reviewed and published shortly, if accepted.

This international conference, in joint collaboration with the Quantum Complex Matter school (QCM2020, http://www.superstripes.net/quantum-complex-matter-2018), will highlight recent advances in all major fields in quantum phenomena in complex condensed matter. This is a multi-purpose meeting based on the Frontiers of Condensed Matter Physics (FCMP) lecture courses and selected topics from the Superstripes conferences. Submissions should focus on the following research subfields:

Correlated electronic systems:

Unconventional superconductivity;

Novel magnetism;

Mott transition;

Quantum criticality;

Multi-band Hubbard model;

Lifshitz transitions.

 

Nano science:

Graphene;

TMDC;

QHE;

Topological;

2D materials;

Fano resonances.

Spintronics:

Skyrmions;

Itinerant electron;

Magnetism;

Spin current;

magnetic memory.

Cold atoms:

Feshbach resonance;

Hubbard model

BEC-BCS crossover.

This Special Issue also welcomes regular submissions from researchers who will not be able to participate in the conference. Your contribution will help this Special Issue to provide additional value to the research community.

Prof. Antonio Bianconi
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 papers will be 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. Condensed Matter is an international peer-reviewed open access quarterly 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 1400 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.

Published Papers (7 papers)

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Research

Open AccessArticle
On the Kinetic Energy Driven Superconductivity in the Two-Dimensional Hubbard Model
Condens. Matter 2021, 6(1), 12; https://doi.org/10.3390/condmat6010012 - 26 Feb 2021
Viewed by 370
Abstract
We investigate the role of kinetic energy for the stability of superconducting state in the two-dimensional Hubbard model on the basis of an optimization variational Monte Carlo method. The wave function is optimized by multiplying by correlation operators of site off-diagonal type. This [...] Read more.
We investigate the role of kinetic energy for the stability of superconducting state in the two-dimensional Hubbard model on the basis of an optimization variational Monte Carlo method. The wave function is optimized by multiplying by correlation operators of site off-diagonal type. This wave function is written in an exponential-type form given as ψλ=exp(λK)ψG for the Gutzwiller wave function ψG and a kinetic operator K. The kinetic correlation operator exp(λK) plays an important role in the emergence of superconductivity in large-U region of the two-dimensional Hubbard model, where U is the on-site Coulomb repulsive interaction. We show that the superconducting condensation energy mainly originates from the kinetic energy in the strongly correlated region. This may indicate a possibility of high-temperature superconductivity due to the kinetic energy effect in correlated electron systems. Full article
(This article belongs to the Special Issue Quantum Complex Matter 2020)
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Open AccessArticle
Potassium-Doped Para-Terphenyl: Structure, Electrical Transport Properties and Possible Signatures of a Superconducting Transition
Condens. Matter 2020, 5(4), 78; https://doi.org/10.3390/condmat5040078 - 01 Dec 2020
Viewed by 810
Abstract
Preliminary evidence for the occurrence of high-TC superconductivity in alkali-doped organic materials, such as potassium-doped p-terphenyl (KPT), were recently obtained by magnetic susceptibility measurements and by the opening of a large superconducting gap as measured by ARPES and STM techniques. In this work, KPT samples have been synthesized by a chemical method and characterized by low-temperature Raman scattering and resistivity measurements. Here, we report the occurrence of a resistivity drop of more than 4 orders of magnitude at low temperatures in KPT samples in the form of compressed powder. This fact was interpreted as a possible sign of a broad superconducting transition taking place below 90 K in granular KPT. The granular nature of the KPT system appears to be also related to the 20 K broadening of the resistivity drop around the critical temperature. Full article
(This article belongs to the Special Issue Quantum Complex Matter 2020)
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Open AccessArticle
Temperature Dependent Structural Evolution of WSe2: A Synchrotron X-ray Diffraction Study
Condens. Matter 2020, 5(4), 76; https://doi.org/10.3390/condmat5040076 - 19 Nov 2020
Viewed by 1003
Abstract
A thorough investigation of the structural parameters of micromechanically exfoliated multilayer WSe2 flakes was undertaken between 400 K to 110 K. Crystal structure of WSe2 remains in the trigonal prismatic structure in this temperature range, however, with a clear difference in [...] Read more.
A thorough investigation of the structural parameters of micromechanically exfoliated multilayer WSe2 flakes was undertaken between 400 K to 110 K. Crystal structure of WSe2 remains in the trigonal prismatic structure in this temperature range, however, with a clear difference in the temperature dependence of the in-plane a, and the out-of-plane c, lattice parameters. The linear coefficients of thermal expansion of a and c are 5.132 × 10−6/K and 8.105 × 10−6/K, respectively. The temperature dependence of the unit-cell volume is analyzed using zero-pressure equation-of-state which yielded the Debye temperature of the WSe2 to be 160 K. Following the temperature dependence of the W-Se and W-W bond distances, a nonlinear behavior is observed in the former in contrast to a rather regular behavior of the later. This significant difference in the temperature dependence of the a and c lattice parameters can have consequences in the macroscopic physical properties of the system. A good correlation between the temperature dependence of the W-Se bond distance and Raman E2g1 mode has been observed. Full article
(This article belongs to the Special Issue Quantum Complex Matter 2020)
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Open AccessArticle
Detection of Spin Polarized Band in VO2/TiO2(001) Strained Films via Orbital Selective Constant Initial State Spectroscopy
Condens. Matter 2020, 5(4), 72; https://doi.org/10.3390/condmat5040072 - 12 Nov 2020
Viewed by 760
Abstract
The VO2 is a 3d1 electron system that undergoes a reversible metal–insulator transition (MIT) triggered by temperature and characterized by an interplay between orbital, charge and lattice degrees of freedom. The characterization of the MIT features are therefore extremely challenging and [...] Read more.
The VO2 is a 3d1 electron system that undergoes a reversible metal–insulator transition (MIT) triggered by temperature and characterized by an interplay between orbital, charge and lattice degrees of freedom. The characterization of the MIT features are therefore extremely challenging and powerful investigation tools are required. In this work, we demonstrate how a combination of resonant photoemission and constant initial state (CIS) spectroscopy can be used as an orbital selective probe of the MIT studying three different VO2/TiO2(001) strained films. The CIS spectra of the V 3d and V 3p photo-electrons shows sensitivity to different orbital contribution and the presence of a spin polarized band close to the Fermi level. Full article
(This article belongs to the Special Issue Quantum Complex Matter 2020)
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Open AccessArticle
Engineering Porous Silicon Nanowires with Tuneable Electronic Properties
Condens. Matter 2020, 5(4), 57; https://doi.org/10.3390/condmat5040057 - 28 Sep 2020
Cited by 2 | Viewed by 840
Abstract
Structural and electronic properties of silicon nanowires with pre-designed structures are investigated. Wires with distinct structure were investigated via advanced spectroscopic techniques such as X-ray absorption spectroscopy and Raman scattering as well as transport measurements. We show that wire structures can be engineered [...] Read more.
Structural and electronic properties of silicon nanowires with pre-designed structures are investigated. Wires with distinct structure were investigated via advanced spectroscopic techniques such as X-ray absorption spectroscopy and Raman scattering as well as transport measurements. We show that wire structures can be engineered with metal assisted etching fabrication process via the catalytic solution ratios as well as changing doping type and level. In this way unique well-defined electronic configurations and density of states are obtained in the synthesized wires leading to different charge carrier and phonon dynamics in addition to photoluminescence modulations. We demonstrate that the electronic properties of these structures depend by the final geometry of these systems as determined by the synthesis process. These wires are characterized by a large internal surface and a modulated DOS with a significantly high number of surface states within the band structure. The results improve the understanding of the different electronic structures of these semiconducting nanowires opening new possibilities of future advanced device designs. Full article
(This article belongs to the Special Issue Quantum Complex Matter 2020)
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Open AccessArticle
Evolution of Spin-Orbital Entanglement with Increasing Ising Spin-Orbit Coupling
Condens. Matter 2020, 5(3), 53; https://doi.org/10.3390/condmat5030053 - 26 Aug 2020
Viewed by 797
Abstract
Several realistic spin-orbital models for transition metal oxides go beyond the classical expectations and could be understood only by employing the quantum entanglement. Experiments on these materials confirm that spin-orbital entanglement has measurable consequences. Here, we capture the essential features of spin-orbital entanglement [...] Read more.
Several realistic spin-orbital models for transition metal oxides go beyond the classical expectations and could be understood only by employing the quantum entanglement. Experiments on these materials confirm that spin-orbital entanglement has measurable consequences. Here, we capture the essential features of spin-orbital entanglement in complex quantum matter utilizing 1D spin-orbital model which accommodates SU(2)⊗SU(2) symmetric Kugel-Khomskii superexchange as well as the Ising on-site spin-orbit coupling. Building on the results obtained for full and effective models in the regime of strong spin-orbit coupling, we address the question whether the entanglement found on superexchange bonds always increases when the Ising spin-orbit coupling is added. We show that (i) quantum entanglement is amplified by strong spin-orbit coupling and, surprisingly, (ii) almost classical disentangled states are possible. We complete the latter case by analyzing how the entanglement existing for intermediate values of spin-orbit coupling can disappear for higher values of this coupling. Full article
(This article belongs to the Special Issue Quantum Complex Matter 2020)
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Open AccessCommunication
Ostwald Growth Rate in Controlled Covid-19 Epidemic Spreading as in Arrested Growth in Quantum Complex Matter
Condens. Matter 2020, 5(2), 23; https://doi.org/10.3390/condmat5020023 - 27 Mar 2020
Cited by 4 | Viewed by 3079
Abstract
Here, we focus on the data analysis of the growth of epidemic spread of Covid-19 in countries where different policies of containment were activated. It is known that the growth of pandemic spread at its threshold is exponential, but it is not known [...] Read more.
Here, we focus on the data analysis of the growth of epidemic spread of Covid-19 in countries where different policies of containment were activated. It is known that the growth of pandemic spread at its threshold is exponential, but it is not known how to quantify the success of different containment policies. We identify that a successful approach gives an arrested phase regime following the Ostwald growth, where, over the course of time, one phase transforms into another metastable phase with a similar free energy as observed in oxygen interstitial diffusion in quantum complex matter and in crystallization of proteins. We introduce the s factor which provides a quantitative measure of the efficiency and speed of the adopted containment policy, which is very helpful not only to monitor the Covid-19 pandemic spread but also for other countries to choose the best containment policy. The results show that a policy based on joint confinement, targeted tests, and tracking positive cases is the most rapid pandemic containment policy; in fact, we found values of 9, 5, and 31 for the success s factor for China, South Korea, and Italy, respectively, where the lowest s factor indicates the best containment policy. Full article
(This article belongs to the Special Issue Quantum Complex Matter 2020)
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