Field-induced superconductivity in MoS2

2013 ◽  
Vol 1549 ◽  
pp. 79-84
Author(s):  
Y. J. Zhang ◽  
J. T. Ye ◽  
Y. Iwasa
Keyword(s):  
Carrier Density ◽  
Gate Dielectric ◽  
Superconducting Phase ◽  
Common Mechanism ◽  
Continuous Control ◽  
Superconducting Transition ◽  
Charge Accumulation ◽  
Density Region ◽  
2D Semiconductors ◽  
Type Conduction

ABSTRACTWe fabricated MoS2 transistor adopting electric double layer (EDL) as gate dielectric. So far, EDL has realized p-type conducting MoS2 in addition to well-known n-type conduction showing ambipolar operation. In our study, field-effect superconducting transition of MoS2 was realized with maximum TC around 10 K. This TC is the highest not only within MoS2 compounds but also among whole TMDs. The highest TC discovered in this study lies in the carrier density region much smaller than chemically investigated region. Such compounds with small doping level have never been successfully synthesized by chemical method. Furthermore, by combining HfO2 (typical high-k material for FETs) gating with EDL gating, continuous control of carrier density, and thus quantum phase, was demonstrated. As a result, we successfully obtained the phase diagram of MoS2. Interestingly, the TC exhibits strong carrier density dependence, showing dome-shaped superconducting phase. Superconducting dome in other materials than cuprates has been reported only a few times in doped 2D semiconductors. Since FET charge accumulation is basically two dimensional, our result implies the existence of common mechanism for superconducting dome in 2D band insulators.

scholarly journals Enhancing Superconductivity of the Nonmagnetic Quasiskutterudites by Atomic Disorder

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5830
Author(s):  
Andrzej Ślebarski ◽  
Maciej M. Maśka
Keyword(s):  
High Temperature ◽  
Transition Temperature ◽  
Superconducting Transition Temperature ◽  
High Temperature Superconductors ◽  
Superconducting Phase ◽  
Length Scale ◽  
Superconducting Transition ◽  
Atomic Disorder ◽  
Strong Inhomogeneity ◽  
Related Compounds

We investigated the effect of enhancement of superconducting transition temperature Tc by nonmagnetic atom disorder in the series of filled skutterudite-related compounds (La3M4Sn13, Ca3Rh4Sn13, Y5Rh6Sn18, Lu5Rh6Sn18; M= Co, Ru, Rh), where the atomic disorder is generated by various defects or doping. We have shown that the disorder on the coherence length scale ξ in these nonmagnetic quasiskutterudite superconductors additionally generates a non-homogeneous, high-temperature superconducting phase with Tc⋆>Tc (dilute disorder scenario), while the strong fluctuations of stoichiometry due to increasing doping can rapidly increase the superconducting transition temperature of the sample even to the value of Tc⋆∼2Tc (dense disorder leading to strong inhomogeneity). This phenomenon seems to be characteristic of high-temperature superconductors and superconducting heavy fermions, and recently have received renewed attention. We experimentally documented the stronger lattice stiffening of the inhomogeneous superconducting phase Tc⋆ in respect to the bulk Tc one and proposed a model that explains the Tc⋆>Tc behavior in the series of nonmagnetic skutterudite-related compounds.

Effects of High-Energy Ball Milling Time on the Sintering Process of FeSe Superconductors

2016 ◽  
Vol 848 ◽  
pp. 657-663 ◽  
Author(s):  
Sheng Nan Zhang ◽  
Xiao Bo Ma ◽  
Ji Xing Liu ◽  
Jian Qing Feng ◽  
Cheng Shan Li ◽  
...  
Keyword(s):  
Phase Composition ◽  
Ball Milling ◽  
Optimal Parameter ◽  
High Energy ◽  
Superconducting Phase ◽  
High Energy Ball Milling ◽  
Superconducting Transition ◽  
Sintering Process ◽  
Energy Ball ◽  
Precursor Powders

FeSe superconducting bulks were prepared with high energy ball milling (HEBM) aided sintering process, within which process, tetragonal β-FeSe superconducting phase could be formed directly with one step sintering process, and the formation of hexagonal δ-FeSe non-superconducting phase was effectively avoided. The influences of HEBM time on the sintering process of FeSe bulks were systematically investigated. With different HEBM time, the phase composition and morphology of precursor powders changed correspondingly, which thus influenced the final phase composition and superconducting properties of FeSe superconducting bulks. Due to the formation of FeSe bulks with larger tetragonal phase content and higher superconducting transition temperature, HEBM time of 6.0 h was recognized as the optimal parameter. Shorter HEBM time could lead to the insufficient decrease of particle size and low density. While longer HEBM time caused the formation of amorphous hexagonal δ-FeSe, which crystallized during sintering process. Thus no more tetragonal FeSe could be obtained. The FeSe superconducting bulk with the critical temperature Tc(onset) of 8.0 K was obtained with the HEBM time of 6 h, and sintering temperature of 700 oC for 12 h.

Superconductivity in the (Nd,Ce,Ca)2Cuo4-Z System

1989 ◽  
Vol 169 ◽  
Author(s):  
Takeshi Sakurai ◽  
Toru Yamashita ◽  
Sumio Ikegawa ◽  
H. Yamauchi
Keyword(s):  
Phase Field ◽  
Carrier Density ◽  
Single Phase ◽  
Superconducting Transition ◽  
X Ray ◽  
Analysis Techniques ◽  
Density Relationship ◽  
Micro Analysis ◽  
T Phase ◽  
Single Phase Field

AbstractWe have controlled the carrier (electron) density in Nd2CuO2 of the T’ structure by introducing both Ce and Ca into the Nd‐sites, and studied the superconducting transition temperature versus carrier density relationship. The phase relations in the (Nd1‐x‐yCexCay)2CuO4‐z system were studied by means of powder X‐ray dirfractron and electron‐probe micro‐analysis techniques. For the phase diagram of the (Nd1‐x‐yCexCay)2CuO4‐z system, the single phase field of the T’ phase was established. Samples of the (Nd0.9‐yCe0.1Cay)2CuO4‐z system with compositions included in the single phase field were synthesized. The carrier density in these samples was varied by controlling the Ca content. The Hall effect and DC resistivity were measured to elucidate the relation between Tc and the carrier density.

HEAT-TREATMENT INFLUENCE ON THE MAGNETIC AND ELECTRIC PROPERTIES OF HIGH-TcYBa2Cu3O7−δ SUPERCONDUCTOR

1996 ◽  
Vol 10 (20) ◽  
pp. 955-961
Author(s):  
LAUREAN HOMORODEAN ◽  
IULIU POP ◽  
ION BURDOI
Keyword(s):  
Heat Treatment ◽  
Electrical Resistivity ◽  
Magnetic Susceptibility ◽  
Room Temperature ◽  
Liquid Nitrogen Temperature ◽  
Superconducting Phase ◽  
Superconducting Transition ◽  
Temperature Dependences ◽  
Magnetic And Electric Properties ◽  
Very High

The changes in the temperature dependences of the magnetic susceptibility and the electrical resistivity of a very-high-T c superconducting YBa 2 Cu 3 O 7−δ sample during the thermal cycling between the liquid-nitrogen temperature and the room temperature are studied. Some singularities corresponding to the superconducting transition, the possible existence of a super-high-temperature superconducting phase and the migration of the oxygen atoms in the Cu-O chains are emphasized on these dependencies.

MAGNETIC, ELECTRIC AND EQUILIBRIUM PROPERTIES OF YBa2Cu3-x(PO4)xO7-δ HIGH TEMPERATURE SUPERCONDUCTING SYSTEM

2009 ◽  
Vol 23 (06) ◽  
pp. 807-813
Author(s):  
M. A. URIBE LAVERDE ◽  
D. A. LANDÍNEZ TÉLLEZ ◽  
J. ROA-ROJAS
Keyword(s):  
Critical Temperature ◽  
Linear Response ◽  
Carrier Density ◽  
Transfer Model ◽  
Superconducting Transition ◽  
Phosphate Content ◽  
X Ray Diffraction ◽  
X Ray ◽  
Heat Capacity Measurements ◽  
Charge Transfer Model

The new YBa 2 Cu 3-x( PO 4)x O 7-δ (x = 0; 0.03; 0.06; 0.09; 0.12) superconducting material was synthesized by the standard solid state reaction recipe. X-ray diffraction results show the effective substitution of copper for phosphate and also show no evidence of any impurity related with phosphate content. Resistivity, DC magnetization and heat capacity measurements reveal a superconducting transition for all samples with a maximum critical temperature up to 97 K, corresponding to the x = 0.03 sample. For higher doping values, the critical temperature decreases in an approximately linear response. In agreement with the charge transfer model, the critical temperature decreases with the carrier density. For x = 0.03, the critical temperature shows a rise up due to an approximation to the optimum density which separates over-doped and under-doped regimes. The maximum critical temperature achieved is one of the highest ever seen for the 123-type superconductors.

NONEQUILIBRIUM THERMODYNAMICS OF JOSEPHSON DEVICES

1996 ◽  
Vol 10 (19) ◽  
pp. 903-908
Author(s):  
ALEC MAASSEN VAN DEN BRINK ◽  
H. DEKKER
Keyword(s):  
Phase Difference ◽  
Nonequilibrium Thermodynamics ◽  
Superconducting Phase ◽  
Josephson Coupling ◽  
Detailed Calculation ◽  
Superconducting Transition ◽  
Tunneling Junction ◽  
Josephson Devices ◽  
First Order ◽  
A Value

The rapid increase of the Josephson free energy as the temperature of a tunneling junction drops below the superconducting transition temperature T c is shown to make this transition of first order in a system in which the phase difference ϕ across the junction is constrained to have a nonzero value. Taking this effect into account, we introduce an availability potential governing the nonisothermal dynamics of the junction which, in contrast with previous results, has no artifacts like latent heat being released upon entering the — high temperature — normal state or a value in this state which depends on the — superconducting — phase difference. The thermodynamic analysis is preceded by a detailed calculation of the Josephson coupling in a model of two ideal BCS superconductors coupled by a tunneling Hamiltonian.

scholarly journals Gate-controlled BCS-BEC crossover in a two-dimensional superconductor

Science ◽  
2021 ◽  
Vol 372 (6538) ◽  
pp. 190-195 ◽  
Author(s):  
Yuji Nakagawa ◽  
Yuichi Kasahara ◽  
Takuya Nomoto ◽  
Ryotaro Arita ◽  
Tsutomu Nojima ◽  
...  
Keyword(s):  
Carrier Density ◽  
Zirconium Nitride ◽  
Einstein Condensation ◽  
Two Dimensional ◽  
Superconducting Transition ◽  
Pseudogap Phase ◽  
Fermion Systems ◽  
Fermi Temperature ◽  
Crossover Behavior ◽  
Bose Einstein

Bardeen-Cooper-Schrieffer (BCS) superfluidity and Bose-Einstein condensation (BEC) are the two extreme limits of the ground state of the paired fermion systems. We report crossover behavior from the BCS limit to the BEC limit realized by varying carrier density in a two-dimensional superconductor, electron-doped zirconium nitride chloride. The phase diagram, established by simultaneous measurements of resistivity and tunneling spectra under ionic gating, demonstrates a pseudogap phase in the low-doping regime. The ratio of the superconducting transition temperature and Fermi temperature in the low–carrier density limit is consistent with the theoretical upper bound expected in the BCS-BEC crossover regime. These results indicate that the gate-doped semiconductor provides an ideal platform for the two-dimensional BCS-BEC crossover without added complexities present in other solid-state systems.

scholarly journals Peculiarities in the concentration dependence of the superconducting transition temperature in the bipolaron theory of Cooper pairs

2017 ◽  
Vol 31 (11) ◽  
pp. 1750125 ◽  
Author(s):  
Victor Lakhno
Keyword(s):  
Transition Temperature ◽  
Concentration Dependence ◽  
Superconducting Transition Temperature ◽  
Superconducting Phase ◽  
Intermediate Level ◽  
Cooper Pairs ◽  
Superconducting Transition

It is shown that the bipolaron theory of Cooper pairs suggests that there is a possibility for a superconducting phase to exist at low and high levels of doping and be absent at the intermediate level of doping. The results obtained possibly to imply the universal character of 1/8 anomaly.

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