Unusual metallic conductivity of high-Tc cuprates

The intrinsic mechanisms of the unusual metallic transports of three types of relevant charge carriers (large polarons, excited (dissociated) polaronic components of bosonic Cooper pairs and bosonic Cooper pairs themselves) along the CuO2 layers of high-Tc cuprates are identified and the new features of metallic conductivity in the CuO2 layers (i.e. ab -planes) of underdoped and optimally doped cuprates are explained. The in-plane conductivity of high-Tc cuprates is associated with the metallic transports of such charge carriers at their scattering by lattice vibrations in thin CuO2 layers. The proposed charge transport theory in high-Tc cuprates allows to explain consistently the distinctive features of metallic conductivity and the puzzling experimental data on the temperature dependences of their in-plane resistivity pab. In underdoped and optimally doped cuprates the linear temperature dependence of pab(T) above the pseudogap formation temperature T∗ is associated with the scattering of polaronic carriers at acoustic and optical phonons, while the different (upward and downward) deviations from the linearity in pab(T) below T∗ are caused by the pseudogap effect on the conductivity of the excited Fermi components of bosonic Cooper pairs and by the dominating conductivity of bosonic Cooper pairs themselves in the normal state of these high-Tc materials.

The Peter Day Series of Magnetic (Super)Conductors

Here, we review the different series of (super)conducting and magnetic radical salts prepared with organic donors of the tetrathiafulvalene (TTF) family and oxalato-based metal complexes (ox = oxalate = C2O42−). Although most of these radical salts have been prepared with the donor bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF = ET), we also include all the salts prepared with other TTF-type donors such as tetrathiafulvalene (TTF), tetramethyl-tetrathiafulvalene (TM-TTF), bis(ethylenediseleno)tetrathiafulvalene (BEST), bis(ethylenedithio)tetraselenafulvalene (BETS) and 4,5bis((2S)-2-hydroxypropylthio)-4’,5’-(ethylenedithio)tetrathiafulvalene (DMPET). Most of the oxalate-based complexes are monomers of the type [MIII(C2O4)3]3−, [Ge(C2O4)3]2− or [Cu(C2O4)2]2−, but we also include the reported salts with [Fe2(C2O4)5]4− dimers, [MII(H2O)2[MIII(C2O4)3]2]4− trimers and homo- or heterometallic extended 2D layers such as [MIIMIII(C2O4)3]− and [MII2(C2O4)3]2−. We will present the different structural families and their magnetic properties (such as diamagnetism, paramagnetism, antiferromagnetism, ferromagnetism and even long-range magnetic ordering) that coexist with interesting electrical properties (such as semiconductivity, metallic conductivity and even superconductivity). We will focus on the electrical and magnetic properties of the so-called Day series formulated as β”-(BEDT-TTF)4[A+MIII(C2O4)3]·G, which represents the largest family of paramagnetic metals and superconductors reported to date, with more than fifty reported examples.

Realizing ultra-stable Ti3C2-MXene in aqueous solution via surface graft with ionomers

MXene is the first class of 2D materials with the combination of metallic conductivity and hydrophilicity. However, degradation forms a key drawback limiting their long term application. This work for...

Observation of itinerant ferromagnetism and coupled magnetoresistance in a spinel CuCo2S4

We report the existence of ferromagnetism in the thiospinel compound CuCo2S4 with Tc ~125K. The magneto-electronic transport of the CuCo2S4 demonstrates a metallic conductivity and positive magnetoresistance at high temperature....

A Review on Synthesis of 2-Dimensional Mn+1X (MXene) materials

The sequence of 2D transition metal carbides, carbonitrides, and nitrides has gained a lot of interest since the discovery of Ti3C2. About thirty new MXene compounds have been identified, with eight different MXene synthesis methods. The presence of surface terminations such as hydroxyl, oxygen, fluorine, or chlorine in the materials described thus far indicates strong hydrophilicity as well as metallic conductivity MXenes are becoming increasingly popular due to their diverse chemistry, which has sparked a surge in academic interest. We will study and examine the many methods of fabricating MXenes in this review, which will cover everything from MAX phase etching to exfoliation, as well as the best approach to synthesise them and their most current applications.

Highly conductive and stable Co9S8 thin films by atomic layer deposition: from process development and film characterization to selective and epitaxial growth

Co9S8 is an interesting sulfide material with metallic conductivity that has shown promise for various energy applications. Herein, we report a new atomic layer deposition process producing crystalline, pure, and...