scholarly journals Evolution of Shape and Volume Fraction of Superconducting Domains with Temperature and Anion Disorder in (TMTSF)2ClO4

Crystals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 72
Author(s):  
Kaushal K. Kesharpu ◽  
Vladislav D. Kochev ◽  
Pavel D. Grigoriev
Keyword(s):  
Cooling Rate ◽  
Annealing Time ◽  
Volume Fraction ◽  
Density Wave ◽  
Spin Density Wave ◽  
Finite Size ◽  
Organic Superconductors ◽  
Organic Superconductor ◽  
Sample Length ◽  
Sample Shape

In highly anisotropic organic superconductor (TMTSF)2ClO4, superconducting (SC) phase coexists with metallic and spin-density wave phases in the form of domains. Using the Maxwell-Garnett approximation (MGA), we calculate the volume ratio and estimate the shape of these embedded SC domains from resistivity data at various temperature and anion disorder, controlled by the cooling rate or annealing time of (TMTSF)2ClO4 samples. We found that the variation of cooling rate and of annealing time affect differently the shape of SC domains. In all cases the SC domains have oblate shape, being the shortest along the interlayer z-axis. This contradicts the widely assumed filamentary superconductivity along the z-axis, used to explain the anisotropic superconductivity onset. We show that anisotropic resistivity drop at the SC onset can be described by the analytical MGA theory with anisotropic background resistance, while the anisotropic Tc can be explained by considering a finite size and flat shape of the samples. Due to a flat/needle sample shape, the probability of percolation via SC domains is the highest along the shortest sample dimension (z-axis), and the lowest along the sample length (x-axis). Our theory can be applied to other heterogeneous superconductors, where the size d of SC domains is much larger than the SC coherence length ξ, e.g., cuprates, iron-based or organic superconductors. It is also applicable when the spin/charge-density wave domains are embedded inside a metallic background, or vice versa.

Syntheses and Properties of k-Phase Organic Superconductors

1992 ◽  
Vol 247 ◽  
Author(s):  
H. Hau Wang ◽  
K. D. Carlson ◽  
U. Geiser ◽  
A. M. Kini ◽  
A. J. Schultz ◽  
...  
Keyword(s):  
Phase Transition ◽  
Ambient Pressure ◽  
Density Wave ◽  
Spin Density Wave ◽  
Organic Superconductors ◽  
Organic Superconductor ◽  
X Ray ◽  
New Class ◽  
Structural Differences ◽  
Similarities And Differences

ABSTRACTThe syntheses and physical properties of K-(ET)2CU[N(CN)2]X (X = Br and Cl) are summarized. The K-(ET)2Cu [N(CN)2] Br salt is the highest Tc radical-cation based ambient pressure organic superconductor (Tc = 11.6 K), and the K-(ET)2CU [N(CN)2] C1 salt becomes a superconductor at even higher Tc under 0.3 kbar hydrostatic pressure (Tc = 12.8 K). The similarities and differences between K-(ET)2Cu[N(CN)2]Br and K-(ET)2CU(NCS)2 (TC = 10.4 K) are presented. The X-ray structures at 127 K reveal that the S-S contacts shorten between ET dimers in the former compound while the S-S contacts shorten within dimers in the latter. The differences in their ESR linewidth behavior is also explained in terms of the structural differences. A semiconducting compound, (ET)Cu[N(CN)2]2, isolated during K-(ET)2Cu[N(CN)2]Cl synthesis is also reported. The ESR measurements of the K-(ET)2Cu[N(CN)2]Cl salt indicate that the phase transition near 40 K is similar to the spin density wave transition in (TMTSF)2SbF6. A new class of organic superconductors, K-(ET)2CU2(CN)3 and K-(ET)2Cu2(CN)3.δBrδ, is reported with Tc's of 2.8 K (1.5 kbar) and 2.6 K (1 kbar), respectively.

Evolution of the spin-density wave-superconductivity texture in the organic superconductor (TMTSF)2PF6 under pressure

2012 ◽  
Vol 407 (11) ◽  
pp. 1806-1809 ◽  
Author(s):  
C.R. Pasquier ◽  
N. Kang ◽  
B. Salameh ◽  
P. Auban-Senzier ◽  
D. Jérome ◽  
...  
Keyword(s):  
Spin Density ◽  
Density Wave ◽  
Spin Density Wave ◽  
Organic Superconductor

Organic superconductors: low-dimensional conductors and anomalous superconductors

1985 ◽  
Vol 314 (1528) ◽  
pp. 69-82
Keyword(s):  
Density Wave ◽  
Spin Density Wave ◽  
Direct Consequence ◽  
Theoretical Models ◽  
Organic Superconductors ◽  
Hall Resistance ◽  
Magnetic Impurities ◽  
Low Dimensionality ◽  
Low Dimensional ◽  
Magnetic States

Organic superconductors belonging to the (TMTSF) 2 X series are quasi-one-dimensional conductors in the sense that their Fermi surface is open. The strong sensitivity of the superconducting state to pressure and non-magnetic impurities is probably a direct consequence of the low-dimensionality of the electron energy dispersion. We discuss the remarkable stabilization of semimetallic (magnetic) states observed under high magnetic fields in (TMTSF) 2 ClO 4 in terms of recently proposed theoretical models. These models suggest the existence of a sequence of phase transitions between spin density wave sub-phases and the quantization of the Hall resistance within each of these sub-phases as observed experimentally.

scholarly journals Coexistence of superconductivity and spin density wave orderings in the organic superconductor (TMTSF) 2 PF 6

2002 ◽  
Vol 25 (3) ◽  
pp. 319-331 ◽  
Author(s):  
T. Vuletić ◽  
P. Auban-Senzier ◽  
C. Pasquier ◽  
S. Tomić ◽  
D. Jérome ◽  
...  
Keyword(s):  
Spin Density ◽  
Density Wave ◽  
Spin Density Wave ◽  
Organic Superconductor

scholarly journals Interface-induced superconductivity at ∼25 K at ambient pressure in undoped CaFe2As2 single crystals

2016 ◽  
Vol 113 (46) ◽  
pp. 12968-12973 ◽  
Author(s):  
Kui Zhao ◽  
Bing Lv ◽  
Liangzi Deng ◽  
Shu-Yuan Huyan ◽  
Yu-Yi Xue ◽  
...  
Keyword(s):  
Low Temperature ◽  
Single Crystals ◽  
Volume Fraction ◽  
Time Window ◽  
Ambient Pressure ◽  
Density Wave ◽  
Spin Density Wave ◽  
Diffraction Profile ◽  
Low Temperature Annealing ◽  
O Phase

Superconductivity has been reversibly induced/suppressed in undoped CaFe2As2 (Ca122) single crystals through proper thermal treatments, with Tc at ∼25 K at ambient pressure and up to 30 K at 1.7 GPa. We found that Ca122 can be stabilized in two distinct tetragonal (T) phases at room temperature and ambient pressure: PI with a nonmagnetic collapsed tetragonal (cT) phase at low temperature and PII with an antiferromagnetic orthorhombic (O) phase at low temperature, depending on the low-temperature annealing condition. Neither phase at ambient pressure is superconducting down to 2 K. However, systematic annealing for different time periods at 350 °C on the as-synthesized crystals, which were obtained by quenching the crystal ingot from 850 °C, reveals the emergence of superconductivity over a narrow time window. Whereas the onset Tc is insensitive to the anneal time, the superconductive volume fraction evolves with the time in a dome-shaped fashion. Detailed X-ray diffraction profile analyses further reveal mesoscopically stacked layers of the PI and the PII phases. The deduced interface density correlates well with the superconducting volume measured. The transport anomalies of the T–cT transition, which is sensitive to lattice strain, and the T–O transition, which is associated with the spin-density-wave (SDW) transition, are gradually suppressed over the superconductive region, presumably due to the interface interactions between the nonmagnetic metallic cT phase and the antiferromagnetic O phase. The results provide the most direct evidence to date for interface-enhanced superconductivity in undoped Ca122, consistent with the recent theoretical prediction.

Superconductivity of κ-(BEDT–TTF)2 Cu[N(CN) 2]Br: Isotope Effect Revisited

1997 ◽  
Vol 488 ◽  
Author(s):  
M. Tokumoto ◽  
N. Kinoshita ◽  
Y. Tanaka ◽  
H. Anzai
Keyword(s):  
Transition Temperature ◽  
Isotope Effect ◽  
Volume Fraction ◽  
Organic Superconductors ◽  
Organic Superconductor ◽  
Superconducting Transition ◽  
Hydrogen Atoms ◽  
Superconducting Volume Fraction ◽  
Cooling Speed ◽  
Inverse Isotope Effect

AbstractIn 1991, we reported a normal isotope effect in organic superconductor κ-(BEDT–TTF)2Cu[N(CN)2]Br, when all the hydrogen atoms of BEDT – TTF were replaced with deuterium. In other words, Tc was depressed by as much as 0.9 K, in contrast to the “inverse isotope effect” commonly observed in 10K-class organic superconductors. Recently, it was reported that the deuterated κ-(BEDT–TTF)2Cu[N(CN)2]Br shows an insulating nature when cooled very rapidly. Therefore, it is necessary for us to reexamine the superconducting transition of both deuterated and undeuterated κ- (BEDT – TTF)2Cu[N(CN)2]Br by SQUID measurements with special attention to the cooling speed. We studied the effect of cooling rate ranging from 10 K/min down to as slow as 0.02 K/min, and observed a significant effect not only on the superconducting transition temperature Tc but also on the superconducting volume fraction.

Fluctuating spin density wave conduction in (TMTSF) 2 X organic superconductors

2011 ◽  
Vol 94 (1) ◽  
pp. 17002 ◽  
Author(s):  
P. Auban-Senzier ◽  
C. R. Pasquier ◽  
D. Jérome ◽  
K. Bechgaard
Keyword(s):  
Spin Density ◽  
Density Wave ◽  
Spin Density Wave ◽  
Organic Superconductors
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