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Intercalation into 1D transition metal trichalcogenides (TMTs) in which fibers are bonded by a weak van der Waals force can be expected to create various intercalation compounds and develop unique physical properties according to the combination of the host materials and guest ions. However, structural changes via intercalation into 1D TMTs are not as simple as those in 2D transition metal dichalcogenides (TMDs) and are still not understood comprehensively. ZrTe3: a typical compound with a 1D trigonal prismatic structure, belongs to TMTs. Herein, through the Ag introduction to ZrTe3 via solid‐state intercalation, a novel crystal phase with a 1D octahedral structure and a quasi‐amorphous (QA) phase during the structural transition are discovered; the QA phase is a novel state of matter in which long‐range order is lost while retaining 1D order. Based on the Ag concentration, the transport properties are flexibly modulated from superconductivity to semiconductivity. Density functional theory calculations indicate the attraction between Ag ions and the pair diffusion due to their attraction. Furthermore, judging the attraction or repulsion between guest ions predicts whether to induce a QA phase or simple lattice expansion like the intercalation into 2D TMDs. [ABSTRACT FROM AUTHOR]

Layered metal nitride halides MNX (M = Ti, Zr, Hf; X = Cl, Br, I) have two polymorphs, including α- and β-forms, which have the FeOCl and SmSI structures, respectively. These compounds are band insulators and become metals and show superconductivity after electron doping by intercalating alkali metals between the layers. The superconductivity of β-form had been extensively characterized from decades ago, but it is not easy to consistently interpret all experimental results using conventional phonon-mediated Bardeen–Cooper–Schriefer mechanisms. The titanium compound TiNCl crystallizes only in the α-form structure. TiNCl also exhibits superconductivity as high as ~16 K after electron doping by intercalating metals and/or organic basis. It is important to compare the superconductivity of different M–N networks. However, α-form compounds are vulnerable to moisture, unlike β-form ones. The intercalation compounds are even more sensitive to humid air. Thus, there are few experimental studies on the superconducting mechanism of α-form, although it has been discussed for exotic Cooper-pairing mechanisms. This short review gathers the recent progress in experimental studies of TiNCl. [ABSTRACT FROM AUTHOR]

“F-free” CeOBiS 2 single crystals have successfully grown, thoroughly eliminating a concern about F-contamination by using a high-purity CsCl flux. The obtained crystals have a plate-like shape with a size of 1.0–3.0 mm in the well-developed plane. Single crystal X-ray structural analysis clearly revealed that the CeOBiS 2 crystallizes with a space group P 4/ nmm (with lattice parameters of a = 4.0189 (6) Å, c = 13.573 (2) Å). The bond valence sum estimation and X-ray photoelectron spectroscopy analysis showed that the chemical state of Ce was in the mixed valence of Ce 3+ and Ce 4+ . The single crystals show superconductivity with zero resistivity at ∼1.3 K. This is the first conclusive evidence of superconductivity driven by Ce valence fluctuation in surely non-doped CeOBiS 2 . The superconducting transition temperature was enhanced up to ∼3.8 K by applying hydrostatic pressure. [ABSTRACT FROM AUTHOR]

Superconducting single crystals of Rb-intercalated FeSe compounds Rb x Fe 2- y Se 2 were prepared by using a starting material of Rb 2 Se as a Rb source. The superconducting properties and the surface microstructures were systematically controlled by varying the cooling rate in the quenching process. The higher cooling rate in the sample provided a higher superconducting transition temperature with highly connected superconducting mesh-like surface structure. Extremely slow-cooling process led to the complete isolation between the superconducting domains. [ABSTRACT FROM AUTHOR]

Cd-doped La(O,F)BiS 2 single crystals were grown using a CsCl/KCl flux. The grown crystals have a plate-like shape with ~1–2 mm square size in a well-developed ab -plane. The Cd doping in the crystals was successfully characterized by single crystal X-ray diffraction and electron probe microanalysis techniques. The superconductivity of La(O,F)BiS 2 was gradually suppressed with Cd doping. The superconducting transition temperature with zero resistivity of La(O 0.54 F 0.46 )(Bi 0.92 Cd 0.08 )S 2 was 2.3 K. The Cd doping does not change the superconducting anisotropy so much, albeit the considerable suppression of T c . [ABSTRACT FROM AUTHOR]

• A synthesizing process of TiNCl has modified • The superconducting properties strongly depend on the synthesis temperature • Optical and photoemission spectroscopy revealed an in-gap state below the E F • Hydrogen emission was detected against the heat treatment of the obtained TiNCl • The in-gap state of hydrogen inhibits the introduction of electron carriers Layered titanium nitride chloride (TiNCl) exhibits a relatively high superconducting transition of ∼16 K, and it is a candidate for the unconventional superconductor. To better understand the superconductivity, we modified the synthesis process for TiNCl. Highly crystalline TiNCl was prepared by chemical vapor transport at different transport temperatures and intercalated with sodium (Na) metal. Although the crystallographic parameters obtained through Rietveld refinement are similar, the superconducting properties strongly depend on the treatment temperature of pristine TiNCl. Optical and photoemission spectroscopy revealed an in-gap state below the Fermi level, indicating hydrogen incorporation, similar to the case of β−ZrNCl. Hydrogen temperature-programmed desorption revealed hydrogen emission against the heat treatment of the obtained pristine TiNCl. The in-gap state of hydrogen inhibits the introduction of electron carriers from the intercalated Na metal. [Display omitted] [ABSTRACT FROM AUTHOR]

We have discovered new members of the Pb-based 1222 layered cuprates containing sulfur of (PbS)Sr(RECe)CuO with RE = Sm, Gd, Dy, and Ho. All the samples are of almost-single 1222 phase. From the ρ- T and χ- T measurements, they are found to be superconductors after annealing under 125 atm O atmosphere at 400 °C. Among them, the sample with RE = Gd is found to show superconductivity at the highest temperature of 30 K. [ABSTRACT FROM AUTHOR]

TiNBr with α-type nitride layers (isostructural with FeOCl) was electron-doped by the intercalation of alkali metal (Li, Na, K, and Rb), which can be cointercalated with organic solvent molecules such as tetrahydrofuran (THF) and propylene carbonate (PC), expanding the basal spacing (d) up to 16 Å. All of the alkali metal intercalation compounds with and without cointercalation become superconductors with transition temperatures (Tc) up to 17.2 K. The Tc varies in a narrow temperature range against a wide range change of 0.1 < x < 0.46 in AxTiNBr. The Tc decreases linearly with the decreasing value of 1/d. The layer structured superconductors show a low anisotropy on the upper critical field (Hc2). These are characteristic features very similar to those found for the intercalation compounds of the Cl homolog TiNCl. [ABSTRACT FROM AUTHOR]

The Zintl compound CaAl2Si2 peritectically decomposes to a new ternary cubic Laves phase Ca(Al,Si)2 and an Al--Si eutectic at temperatures above 750 °C under a pressure of 13 GPa. The ternary Laves phase compound can also be prepared as solid solutions Ca(Al1-xSix)2 (0.35 ≤ x ≤ 0.75) directly from the ternary mixtures under high-pressure and high-temperature conditions. The cubic Laves phase structure can be regarded as a type of clathrate compound composed of face-sharing truncated tetrahedral cages with Ca atoms at the center, Ca@(Al,Si)12. The compound with a stoichiometric composition CaAlSi exhibits superconductivity with a transition temperature of 2.6 K. This is the first superconducting Laves phase compound composed solely of commonly found elements. [ABSTRACT FROM AUTHOR]

A new family of the Pb-based layered cuprate with the 1222 structure has been synthesized in the (Pb,S)Sr(RE,Ce)CuO (RE=Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, and Y) system. The almost-single phase samples are obtained for x=0.25 and y=1.0 in the composition of (PbS)Sr(RECe)CuO. Each of the samples has the crystal structure with a tetragonal symmetry. Both of the lattice parameters a and c are decreasing with the decrease of the ionic radius of RE element. Among these samples, the sample with RE=Er has the smallest resistivity in the whole temperature range and the slope of the resistivity versus temperature is the most gentle. Despite annealing under O atmosphere at high-pressure of 121 atm, this sample is a semiconductor with the transport process characteristics of three-dimensional variable range hopping conduction. Then the samples of RE=Er with smaller y are investigated for the composition of (PbS)Sr(RECe)CuO, the sample with y=0.4 is found to show an onset of resistivity drop phenomenon at about 11 K with the decrease of temperature. Moreover, we also discover that the samples of RE=Ho with y=0.4 show an onset of the resistivity dropping at over 20 K and zero resistivity at 13 K. From these results, the present (PbS)Sr(RECe)CuO system is considered to be a new family of the Pb-based superconducting cuprates with the 1222 structure. [ABSTRACT FROM AUTHOR]

We have synthesized new Pb-based 1222 cuprates containing sulfur in the (PbS)Sr(EuCe)CuO system. X-ray diffraction study shows that almost the single 1222 phase samples can be obtained for a considerable wide area of 0.3≤ x≤1.2 in the composition of (PbS)Sr(EuCe)CuO. Next, the sample with x=0.4 after annealing under high-pressure O is discovered to show an onset of the resistivity drop at about 31 K and to show an onset of diamagnetic signal at about 29 K. These phenomena clearly indicate that the sample is a new superconductor. [ABSTRACT FROM AUTHOR]

Titanium nitride chloride (TiNCl), a band semiconductor with the a-form layered structure, becomes a superconductor with a transition temperature Tc &ap; 18.0 K by electron doping via alkali-metal intercalation. Upon cointercalation of various kinds of organic solvent molecules with alkali atoms, the superconducting layered crystals are swelled to different extents adjusting to the size of the molecules, and the Tc decreases linearly down to 6.5 K as a function of I/d, where d is the interlayer separation (basal spacing) of the expanded nitride layers, implying the importance of the Coulomb interlayer coupling for superconductivity. This is in strong contrast to a previous finding that the Tc of the electron-doped ZrNCl and HfNCl with the &bgr;-form layered structure rather increases with the increase of d upon a similar cointercalation of solvent molecules. [ABSTRACT FROM AUTHOR]

We previously reported on the synthesis of new Pb-based 1222 superconductor containing phosphorus in the (PbP)Sr(EuCeSr)CuO system. Recently, we have discovered new members of the Pb-based 1222 superconductor containing phosphorus in the (PbP)Sr(LnCeSr)CuO (Ln=Sm and Gd) systems. In each system, it is found that the samples of almost the single 1222 phase can be obtained for a wide composition area of 0.3≤ x≤1.0. After annealing under 143 atm O atmosphere at 400 °C, each sample of Ln=Sm and Gd with x=0.3 is found to show an onset of resistivity-drop at about 28 K and at about 24 K, respectively. Moreover, each samples of Ln=Sm and Gd is found to show an onset of diamagnetic signal at about 25 K and about 22 K, respectively. From these facts, these samples of Ln=Sm and Gd are found to be new members of the Pb-based 1222 superconductor containing phosphorus. [ABSTRACT FROM AUTHOR]

New Pb-based 1222 cuprates containing phosphorus have been synthesized in the (PbP)Sr- (RECeSr)CuO (RE = Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Y) systems. The almost-single phase samples are obtained for 0.5≤ x≤1.0 and y=0.1 in the cases of RE = Nd, Dy, Ho, Er, Tm, Yb and Y, while for 0.3≤ x≤1.0 and y=0.1 in the cases of RE = Sm, Eu and Gd. The samples crystallize in a tetragonal lattice, the lattice parameters a and c are decreasing with the decrease of the ionic radius of the RE element. Even after annealing under 143 atm O atmosphere at 400 °C, almost all the samples with the common values x=0.5 and y=0.1 are semiconductors with a transport process followed by three-dimensional variable range hopping. However, the samples of RE = Sm, Eu and Gd, which are of almost single 1222 phase, even for x=0.3 and y=0.1, show superconductivity with the onsets at about 25 K, 20 K and 22 K, respectively. Through this study, we find very important procedure for discovery of new superconducting 1222 compound. [ABSTRACT FROM AUTHOR]

The Pb-based 1212 compounds containing phosphorus were already discovered by us in the (Pb,P)Sr(Y,Ca)CuO system. Among the almost-single phase samples, a sample with the nominal composition of (PbP)Sr(YCa)CuO was a superconductor with the highest T of 38 K in the system. Recently, we have been investigating on substitution effect of Ba for Sr on superconductivity in the (PbP)(SrBa)(YCa)CuO system. As a result, it is found that the almost-single 1212 phase samples are obtained in the composition area of 0.0≤ x≤0.4. In this area, with increase of x, the lattice parameters a, c and the cell volume V are found to be gradually increasing. This finding can be considered to show that larger Ba ions certainly occupied the Sr-sites in the sample. However, we obtain such interesting results as that the T value is not so enhanced by the substitution in comparison with that of the sample of x=0.0, and that the maximum value of T was 40 K for x=0.2 and 0.3 at the best. [ABSTRACT FROM AUTHOR]

We previously reported on discovery of new Pb-based 1232 cuprate containing boron in the (PbB)Sr(ErCeSr)CuO system. Recently, a new member of the Pb-based 1232 cuprates containing boron has been synthesized in the (PbB)Sr(RECeSr)CuO systems (RE=Ho, Tm, and Y). In each system, almost the single 1232 phase samples are found to be obtained for the composition area of x=1.7-1.9 and y=0.2, and the sample with x=1.7 is found to show the smallest resistivity. Despite of annealing under 142 atm O atmosphere at 400 °C for 4 h, the sample with x=1.7 in each system is a semiconductor with the transport process followed by a three-dimensional variable range hopping conduction. Moreover, it is found that the sample with RE=Ho shows magnetic anomalies at two temperatures of about 11 and 16 K, and the sample with RE=Y shows a diamagnetic signal at about 8 K, respectively. [ABSTRACT FROM AUTHOR]

New Pb-based 1212 compounds containing phosphorus have been discovered in the (PbP)Sr(YCa)CuO system; almost the single 1212 phase samples can be obtained for the composition range of 0.0≤ x≤0.6 and y=0.25. The crystal structure for each sample has a tetragonal symmetry with the typical lattice parameters a=0.3828 nm and c=1.182 nm. Among them, the sample with x=0.6 and y=0.25 shows the onset of resistivity drop at about 39 K and zero-resistivity at about 17 K. Moreover, the sample shows a diamagnetic signal at about 38 K. These phenomena are found to originate from superconductivity with the bulk feature. [ABSTRACT FROM AUTHOR]

New Pb-based layered cuprates containing boron with the 1232 structure have been synthesized in the (PbB)Sr(ErCeSr)CuO system. Nearly the single 1232 phase samples are obtained for the nominal composition of 1.6≤ x≤1.9 and y=0.2. A sample with the composition of (PbB)Sr(ErCeSr)CuO shows resistivity-dropping phenomenon below 10 K and it shows a diamagnetic signal at about 9.0 K, though the superconducting volume fraction is very small. From these results, the sample may well be a new Pb-based superconductor with the 1232 structure. [ABSTRACT FROM AUTHOR]

We have already reported on substitution effects of Ba for Sr in the sulfur contained Pb-based 1212 compound with the composition of (PbS)(SrBa) (YCa)CuO. It was found that each sample with x=0.3-0.6 showed a resistivity drop originating from superconductivity, and the highest onset temperature of the drop was about 32 K for a sample with x=0.5, but the volume fraction was very small. More recently, we have investigated effect of high-pressure O annealing on superconductivity of the Ba-substituted samples with x=0.4-0.6. As a result, the sample with x=0.5 is found to show an onset of the resistivity drop at the highest temperature of about 41.7 K and it shows an onset of the diamagnetic signal at about 42.0 K. These transition temperatures are higher by ∼10 K than those of the previously reported sample with x=0.5. Moreover, the superconducting volume fraction is increasing more by the high-pressure O annealing. These results indicate that the high-pressure O annealing effectively promotes superconductivity of the present (PbS)(SrBa)(YCa)CuO system. [ABSTRACT FROM AUTHOR]

Superconducting FeSe films were electrochemically deposited on rolling-assisted biaxially textured substrate (RABiTS) tape. We observed zero resistivity in the as-electrodeposited FeSe film prepared on the RABiTS when the appropriate voltage was applied while it was dipped into the solution. When the RABiTS tape was dipped in the solution without applying voltage, a thin Se film was deposited on the substrate. The compositional ratio of the FeSe film got closer to the stoichiometric ratio with decreasing the dipping time before applying voltage. [ABSTRACT FROM AUTHOR]

Ca(Al1-xSix)2 (0.15 ≤ x ≤ 0.75) phases are prepared by arc melting of CaSi2 and Al followed by RF induction heating (1000-1200 °C, 3 h). [ABSTRACT FROM AUTHOR]

Superconductivity is successfully induced by utilizing a battery-like reaction found in a typical Li-ion battery. Excess Fe in FeTe 0.8 S 0.2 is electrochemically de-intercalated by applying a voltage in a citric acid solution. The superconducting properties improve with an increase in the applied voltage up to 1.5 V. This result suggests that an electrochemical reaction can be used as a novel method to develop new superconducting materials. [ABSTRACT FROM AUTHOR]

From field-angle dependent Andreev reflection spectroscopy on single crystals of La(O,F)BiSeS, which belongs to the recently discovered BiCh 2 (Ch = S, Se) based layered superconductors, we found that the superconductivity in La(O,F)BiSeS is highly anisotropic. We measured a superconducting energy gap of 0.61 meV for current injected along c -axis at 1.5 K. Detailed temperature and magnetic field dependent studies of the gap also reveal the presence of unconventional pairing in La(O,F)BiSeS. We show that the observed anisotropic superconducting properties can be attributed to the anisotropy in the superconducting order parameter with a complex symmetry in superconducting La(O,F)BiSeS. [ABSTRACT FROM AUTHOR]