Special Issue "Selected Papers from Quantum Complex Matter 2018"

A special issue of Condensed Matter (ISSN 2410-3896).

Deadline for manuscript submissions: closed (30 September 2019).

Special Issue Editors

Prof. Antonio Bianconi
E-Mail Website
Guest Editor
Rome International Center for Materials Science Superstripes (RICMASS), Via dei Sabelli 119A, 00185 Roma, Italy
Tel. +39 3388438281; Fax: +39 06 4957697
Interests: Experimental methods: synchrotron radiation research, XANES spectroscopy, many body effects in XANES, scanning micro x-ray diffraction; Materials: transition metal oxides, high Tc superconductors, metallo-proteins, biological systems; Quantum phenomena in complex matter: lattice and electronic complexity, polymorphism, valence fluctuation, multi-band Hubbard models, superstripes, nanoscale electronic phase separation, protein fluctuations, effective charge and coordination in active sites of metalloproteins, origin of life
Special Issues and Collections in MDPI journals
Prof. Dr. Augusto Marcelli
E-Mail Website
Guest Editor
Laboratori Nazionali di Frascati Istituto Nazionale di Fisica Nucleare, Via E. Fermi 40, I-00044 Frascati (Rome) Italy
Interests: synchrotron radiation research; synchrotron radiation instrumentation: IR and x-ray optics; x-ray absorption spectroscopy; circular magnetic x-ray dichroism; time resolved concurrent experiments; high Tc superconductors and quantum materials; multiple scattering theory applied to core level x-ray absorption spectra; dust and aerosol characterization and ultra-trace detection; FTIR spectromicroscopy and imaging applied to protein, cells and tissues
Special Issues and Collections in MDPI journals
Prof. Dr. Yasutomo Uemura
E-Mail
Guest Editor
Department of Physics, Columbia University, 538 West 120th Street, 704 Pupin Hall MC 5255, New York, NY 10027, USA
Interests: muon spin relaxation spectroscopy MuSR; neutron scattering; strongly correlated systems; unconventional superconductivity; novel magnetism; spin fluctuations and excitations in random magnetic systems, such as spin glasses and fractal spin networks
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

This Special Issue will publish selected papers from the QCM 2018 conference lectures, joint with the QCM school, 10–16 June, 2018, in Rome, Italy. You are invited to submit a full manuscript for consideration and possible publication in this joint Special Issue. Submissions will be rapidly reviewed and published immediately, free of charge, if accepted. A second issue is reserved for contributions on the same topics that were not presented at the Rome conference or school.

The international conference, joint with the school on Quantum Complex Matter 2018 (QCM2018, 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 of activities based on the Frontiers of Condensed Matter Physics (FCMP) lecture courses and selected topics of Superstripes conferences. Invited and leading contributed papers will focus on research sub-fields of:

Correlated electronic systems:

  • unconventional superconductivity
  • novel magnetism
  • Mott transition
  • quantum criticality
  • multi-band Hubbard model
  • Lifshitz transitions

Nano science:

  • graphene
  • TMDC
  • QHE
  • Topological
  • 2-D materials
  • Fano resonances

Spintronics:

  • Skyrmions
  • itinerant electron
  • magnetism
  • spin current
  • magnetic memory

Cold atoms:

  • Feshbach Resonance
  • Hubbard Model
  • BEC-BCS crossover

to promote discussion and collaboration among researchers of different sub-fields. The QCM 2018 conference is integrated with the QCM 2018 school with educational courses for students and young researchers. The lecture contents of the course will be announced later.

The other more information about this conference could be found at: https://www.mdpi.com/journal/condensedmatter/events/7005

Prof. Antonio Bianconi
Prof. Dr. Augusto Marcelli
Prof. Dr. Yasutomo Uemura
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 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 1000 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 (9 papers)

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

Research

Jump to: Review

Open AccessArticle
Direct Visualization of Spatial Inhomogeneity of Spin Stripes Order in La1.72Sr0.28NiO4
Condens. Matter 2019, 4(3), 77; https://doi.org/10.3390/condmat4030077 - 10 Aug 2019
Abstract
In several strongly correlated electron systems, the short range ordering of defects, charge and local lattice distortions are found to show complex inhomogeneous spatial distributions. There is growing evidence that such inhomogeneity plays a fundamental role in unique functionality of quantum complex materials. [...] Read more.
In several strongly correlated electron systems, the short range ordering of defects, charge and local lattice distortions are found to show complex inhomogeneous spatial distributions. There is growing evidence that such inhomogeneity plays a fundamental role in unique functionality of quantum complex materials. La1.72Sr0.28NiO4 is a prototypical strongly correlated perovskite showing spin stripes order. In this work we present the spatial distribution of the spin order inhomogeneity by applying micro X-ray diffraction to La1.72Sr0.28NiO4, mapping the spin-density-wave order below the 120 K onset temperature. We find that the spin-density-wave order shows the formation of nanoscale puddles with large spatial fluctuations. The nano-puddle density changes on the microscopic scale forming a multiscale phase separation extending from nanoscale to micron scale with scale-free distribution. Indeed spin-density-wave striped puddles are disconnected by spatial regions with negligible spin-density-wave order. The present work highlights the complex spatial nanoscale phase separation of spin stripes in nickelate perovskites and opens new perspectives of local spin order control by strain. Full article
(This article belongs to the Special Issue Selected Papers from Quantum Complex Matter 2018)
Show Figures

Figure 1

Open AccessArticle
Q Dependence of Magnetic Resonance Mode on FeTe0.5Se0.5 Studied by Inelastic Neutron Scattering
Condens. Matter 2019, 4(3), 69; https://doi.org/10.3390/condmat4030069 - 12 Jul 2019
Abstract
Inelastic neutron scattering measurements have been performed on a superconducting single crystal FeTe 0.5 Se 0.5 to examine the Q -dependent enhancement of the dynamical structure factor, S ( Q , E ) , from Q = (0, 0) to ( π , [...] Read more.
Inelastic neutron scattering measurements have been performed on a superconducting single crystal FeTe 0.5 Se 0.5 to examine the Q -dependent enhancement of the dynamical structure factor, S ( Q , E ) , from Q = (0, 0) to ( π , π ), including ( π , 0) in the superconducting state. In most of iron-based superconductors, S ( Q , E ) is enhanced at Q = ( π , 0), where the “magnetic resonance mode” is commonly observed in the unfolded Brillouin zone. Constant-E cuts of S ( Q , E ) suggest that the enhancement is not uniform in the magnetic excitation, and limited around Q = ( π , 0). This result is consistent with the theoretical simulation of the magnetic resonance mode due to the Bardeen–Cooper–Schrieffer coherence factor with the sign-reversing order parameter of s ± wave. Full article
(This article belongs to the Special Issue Selected Papers from Quantum Complex Matter 2018)
Show Figures

Figure 1

Open AccessArticle
Substrate-Induced Proximity Effect in Superconducting Niobium Nanofilms
Condens. Matter 2019, 4(1), 4; https://doi.org/10.3390/condmat4010004 - 30 Dec 2018
Abstract
Structural and superconducting properties of high-quality niobium nanofilms with different thicknesses are investigated on silicon oxide (SiO2) and sapphire substrates. The role played by the different substrates and the superconducting properties of the Nb films are discussed based on the defectivity [...] Read more.
Structural and superconducting properties of high-quality niobium nanofilms with different thicknesses are investigated on silicon oxide (SiO2) and sapphire substrates. The role played by the different substrates and the superconducting properties of the Nb films are discussed based on the defectivity of the films and on the presence of an interfacial oxide layer between the Nb film and the substrate. The X-ray absorption spectroscopy is employed to uncover the structure of the interfacial layer. We show that this interfacial layer leads to a strong proximity effect, especially in films deposited on a SiO2 substrate, altering the superconducting properties of the Nb films. Our results establish that the critical temperature is determined by an interplay between quantum-size effects, due to the reduction of the Nb film thicknesses, and proximity effects. The detailed investigation here provides reference characterizations and has direct and important implications for the fabrication of superconducting devices based on Nb nanofilms. Full article
(This article belongs to the Special Issue Selected Papers from Quantum Complex Matter 2018)
Show Figures

Figure 1

Open AccessArticle
The Magnetic Properties of 1111-type Diluted Magnetic Semiconductor (La1−xBax)(Zn1−xMnx)AsO in the Low Doping Regime
Condens. Matter 2018, 3(4), 42; https://doi.org/10.3390/condmat3040042 - 29 Nov 2018
Abstract
We investigated the magnetic properties of (La 1 x Ba x )(Zn 1 x Mn x )AsO with x varying from 0.005 to 0.05 at an external magnetic field of 1000 Oe. For doping levels of x ≤ 0.01, the system [...] Read more.
We investigated the magnetic properties of (La 1 x Ba x )(Zn 1 x Mn x )AsO with x varying from 0.005 to 0.05 at an external magnetic field of 1000 Oe. For doping levels of x ≤ 0.01, the system remains paramagnetic down to the lowest measurable temperature of 2 K. Only when the doping level increases to x = 0.02 does the ferromagnetic ordering appear. Our analysis indicates that antiferromagnetic exchange interactions dominate for x ≤ 0.01, as shown by the negative Weiss temperature fitted from the magnetization data. The Weiss temperature becomes positive, i.e., ferromagnetic coupling starts to dominate, for x ≥ 0.02. The Mn-Mn spin interaction parameter 2 J / k B is estimated to be in the order of 10 K for both x ≤ 0.01 (antiferromagnetic ordered state) and x ≥ 0.02 (ferromagnetic ordered state). Our results unequivocally demonstrate the competition between ferromagnetic and antiferromagnetic exchange interactions in carrier-mediated ferromagnetic systems. Full article
(This article belongs to the Special Issue Selected Papers from Quantum Complex Matter 2018)
Show Figures

Figure 1

Open AccessArticle
Negative Energy Antiferromagnetic Instantons Forming Cooper-Pairing ‘Glue’ and ‘Hidden Order’ in High-Tc Cuprates
Condens. Matter 2018, 3(4), 39; https://doi.org/10.3390/condmat3040039 - 07 Nov 2018
Cited by 1
Abstract
An emergence of magnetic boson of instantonic nature, that provides a Cooper-‘pairing glue’, is considered in the repulsive ‘nested’ Hubbard model of superconducting cuprates. It is demonstrated that antiferromagnetic instantons of a spin density wave type may have negative energy due to coupling [...] Read more.
An emergence of magnetic boson of instantonic nature, that provides a Cooper-‘pairing glue’, is considered in the repulsive ‘nested’ Hubbard model of superconducting cuprates. It is demonstrated that antiferromagnetic instantons of a spin density wave type may have negative energy due to coupling with Cooper pair condensate. A set of Eliashberg like equations is derived and solved self-consistently, proving the above suggestion. An instantonic propagator plays the role of the Green function of the pairing ‘glue’ boson. Simultaneously, the instantons defy condensation of the mean-field spin-density wave (SDW) order. We had previously demonstrated in analytical form that periodic chain of instanton-anti-instanton pairs along the axis of Matsubara time has zero scattering cross section for weakly perturbing external probes, like neutrons, etc., thus representing a ‘hidden order’. Hence, the two competing orders, superconducting and antiferromagnetic, may coexist (below some T c ) in the form of the superconducting order coupled to ‘hidden’ instantonic one. This new picture is discussed in relation with the mechanism of high temperature superconductivity. Full article
(This article belongs to the Special Issue Selected Papers from Quantum Complex Matter 2018)
Show Figures

Figure 1

Open AccessArticle
Majorana Fermions in One-Dimensional Structures at LaAlO3/SrTiO3 Oxide Interfaces
Condens. Matter 2018, 3(4), 37; https://doi.org/10.3390/condmat3040037 - 29 Oct 2018
Cited by 2
Abstract
We study one-dimensional structures that may be formed at the LaAlO 3 /SrTiO 3 oxide interface by suitable top gating. These structures are modeled via a single-band model with Rashba spin-orbit coupling, superconductivity and a magnetic field along the one-dimensional chain. We first [...] Read more.
We study one-dimensional structures that may be formed at the LaAlO 3 /SrTiO 3 oxide interface by suitable top gating. These structures are modeled via a single-band model with Rashba spin-orbit coupling, superconductivity and a magnetic field along the one-dimensional chain. We first discuss the conditions for the occurrence of a topological superconducting phase and the related formation of Majorana fermions at the chain endpoints, highlighting a close similarity between this model and the Kitaev model, which also reflects in a similar condition the formation of a topological phase. Solving the model in real space, we also study the spatial extension of the wave function of the Majorana fermions and how this increases with approaching the limit condition for the topological state. Using a scattering matrix formalism, we investigate the stability of the Majorana fermions in the presence of disorder and discuss the evolution of the topological phase with increasing disorder. Full article
(This article belongs to the Special Issue Selected Papers from Quantum Complex Matter 2018)
Show Figures

Figure 1

Open AccessArticle
Crossover Induced Electron Pairing and Superconductivity by Kinetic Renormalization in Correlated Electron Systems
Condens. Matter 2018, 3(3), 26; https://doi.org/10.3390/condmat3030026 - 06 Sep 2018
Cited by 1
Abstract
We investigate the ground state of strongly correlated electron systems based on an optimization variational Monte Carlo method to clarify the mechanism of high-temperature superconductivity. The wave function is optimized by introducing variational parameters in an exponential-type wave function beyond the Gutzwiller function. [...] Read more.
We investigate the ground state of strongly correlated electron systems based on an optimization variational Monte Carlo method to clarify the mechanism of high-temperature superconductivity. The wave function is optimized by introducing variational parameters in an exponential-type wave function beyond the Gutzwiller function. The many-body effect plays an important role as an origin of superconductivity in a correlated electron system. There is a crossover between weakly correlated region and strongly correlated region, where two regions are characterized by the strength of the on-site Coulomb interaction U. We insist that high-temperature superconductivity occurs in the strongly correlated region. Full article
(This article belongs to the Special Issue Selected Papers from Quantum Complex Matter 2018)
Show Figures

Figure 1

Open AccessArticle
On the Evaluation of the Spin Galvanic Effect in Lattice Models with Rashba Spin-Orbit Coupling
Condens. Matter 2018, 3(3), 22; https://doi.org/10.3390/condmat3030022 - 24 Jul 2018
Abstract
The spin galvanic effect (SGE) describes the conversion of a non-equilibrium spin polarization into a charge current and has recently attracted renewed interest due to the large conversion efficiency observed in oxide interfaces. An important factor in the SGE theory is disorder which [...] Read more.
The spin galvanic effect (SGE) describes the conversion of a non-equilibrium spin polarization into a charge current and has recently attracted renewed interest due to the large conversion efficiency observed in oxide interfaces. An important factor in the SGE theory is disorder which ensures the stationarity of the conversion. Through this paper, we propose a procedure for the evaluation of the SGE on disordered lattices which can also be readily implemented for multiband systems. We demonstrate the performance of the method for a single-band Rashba model and compare our results with those obtained within the self-consistent Born approximation for a continuum model. Full article
(This article belongs to the Special Issue Selected Papers from Quantum Complex Matter 2018)
Show Figures

Figure 1

Review

Jump to: Research

Open AccessReview
Anomalous Transport Behavior in Quantum Magnets
Condens. Matter 2018, 3(4), 30; https://doi.org/10.3390/condmat3040030 - 10 Oct 2018
Cited by 1
Abstract
Transport behavior that is characterized by a low-temperature electrical resistivity that displays a power law behavior ( ρ ( T 0 ) T s ) with an exponent of s < 2 is commonly observed in magnetic materials in both the [...] Read more.
Transport behavior that is characterized by a low-temperature electrical resistivity that displays a power law behavior ( ρ ( T 0 ) T s ) with an exponent of s < 2 is commonly observed in magnetic materials in both the magnetic and non-magnetic phases. We give a pedagogical overview of this phenomenon that summarizes both the experimental situation and the state of its theoretical understanding. We also put it in context by drawing parallels with unusual power law transport behavior in other systems. Full article
(This article belongs to the Special Issue Selected Papers from Quantum Complex Matter 2018)
Show Figures

Figure 1

Back to TopTop