scholarly journals Inverse correlation between quasiparticle mass and Tc in a cuprate high-Tc superconductor

2016 ◽  
Vol 2 (3) ◽  
pp. e1501657 ◽  
Author(s):  
Carsten Putzke ◽  
Liam Malone ◽  
Sven Badoux ◽  
Baptiste Vignolle ◽  
David Vignolles ◽  
...  
Keyword(s):  
High Temperature Superconductivity ◽  
Inverse Correlation ◽  
Charge Order ◽  
Quantum Fluctuations ◽  
Quantum Oscillation ◽  
Strong Increase ◽  
Electron Mass ◽  
Superconducting Transition ◽  
Optimal Doping ◽  
A Charge

Close to a zero-temperature transition between ordered and disordered electronic phases, quantum fluctuations can lead to a strong enhancement of electron mass and to the emergence of competing phases such as superconductivity. A correlation between the existence of such a quantum phase transition and superconductivity is quite well established in some heavy fermion and iron-based superconductors, and there have been suggestions that high-temperature superconductivity in copper-oxide materials (cuprates) may also be driven by the same mechanism. Close to optimal doping, where the superconducting transition temperature Tc is maximal in cuprates, two different phases are known to compete with superconductivity: a poorly understood pseudogap phase and a charge-ordered phase. Recent experiments have shown a strong increase in quasiparticle mass m* in the cuprate YBa2Cu3O7-δ as optimal doping is approached, suggesting that quantum fluctuations of the charge-ordered phase may be responsible for the high-Tc superconductivity. We have tested the robustness of this correlation between m* and Tc by performing quantum oscillation studies on the stoichiometric compound YBa2Cu4O8 under hydrostatic pressure. In contrast to the results for YBa2Cu3O7-δ, we find that in YBa2Cu4O8, the mass decreases as Tc increases under pressure. This inverse correlation between m* and Tc suggests that quantum fluctuations of the charge order enhance m* but do not enhance Tc.

Structure and Dynamics of NaxCoO2 and the Hydrated Superconductor

2004 ◽  
Vol 840 ◽  
Author(s):  
J. W. Lynn ◽  
Q. Huang ◽  
R. J. Cava ◽  
Y. S. Lee
Keyword(s):  
Structural Model ◽  
Parent Compound ◽  
Inverse Correlation ◽  
Basic Structure ◽  
High Energy ◽  
High Symmetry ◽  
Superconducting Transition ◽  
First Order ◽  
Special Cases ◽  
A Charge

ABSTRACTThe properties of the NaxCoO2 class of materials are of interest from a number of viewpoints. These compounds are based on a triangular lattice of spin-½ ions—prototype RVB system— where a high thermoelectric-power Curie-Weiss metallic paramagnet is found for Na0.7CoO2, a charge ordered insulator at x=0.5, and a paramagnetic metal where superconductivity is induced in Na0.3CoO2 when it is intercalated with water. Here we briefly review our neutron diffraction and inelastic scattering measurements characterizing the crystal structure and lattice dynamics, and relate these to the observed physical properties. The basic structure of NaxCoO2 is hexagonal and consists of robust layers of CoO2 interspersed by Na layers with two inequivalent sites. Two special cases are x=1 where one of these sites is fully occupied and the other empty, and x=½ where both sites have equal occupancies of ¼ and the system is a charge ordered insulator. For general × the site occupancies are inequivalent and vary systematically with x. In the regime of x=0.75 we find a first-order transition from a high symmetry Na site at low T to a three-fold split site (with lower symmetry) at high T. This transition is first order and varies with x. For the Na0.3CoO2. 1.4(H/D)2O superconductor, the water forms two additional layers between the Na and CoO2, increasing the c -axis lattice parameter of the hexagonal P 63/mmc space group from 11.16 Å to 19.5 Å. The Na ions are found to occupy a different configuration from the parent compound, while the water forms a structure that replicates the structure of ice to a good approximation. We find a strong inverse correlation between the CoO2 layer thickness and the superconducting transition temperature (TC increases with decreasing thickness). The phonon density-of-states for Na0.3CoO2 exhibits distinct acoustic and optic bands, with a high-energy cutoff of ∼100 meV. The lattice dynamical scattering for the superconductor is dominated by the hydrogen modes, with librational and bending modes that are quite similar to ice, supporting the structural model that the water intercalates and forms ice-like layers in the superconductor.

scholarly journals Magnetic monopole mechanism for localized electron pairing in HTS

2021 ◽  
Author(s):  
Cristina Diamantini ◽  
Carlo Trugenberger ◽  
Valerii Vinokur
Keyword(s):  
High Temperature Superconductivity ◽  
Magnetic Monopoles ◽  
Real Space ◽  
Effective Field ◽  
Superconducting Transition ◽  
Infinite Cluster ◽  
Electron Pairing ◽  
Pseudogap Phase ◽  
Topological Quantum ◽  
A Charge

Abstract Recent effective field theory of high-temperature superconductivity (HTS) captures the universal features of HTS and the pseudogap phase and explains the underlying physics as a coexistence of a charge condensate with a condensate of dyons, particles carrying both magnetic and electric charges. Central to this picture are magnetic monopoles emerging in the proximity of the topological quantum superconductor-insulator transition (SIT) that dominates the HTS phase diagram. However, the mechanism responsible for spatially localized electron pairing, characteristic of HTS, remains elusive. Here we show that real-space, localized electron pairing is mediated by magnetic monopoles and occurs well above the superconducting transition temperature Tc. Localized electron pairing promotes the formation of superconducting granules connected by Josephson links. Global superconductivity sets in when these granules form an infinite cluster at Tc, which is estimated to fall in the range from hundred to thousand Kelvins. Our findings pave the way to tailoring materials with elevated superconducting transition temperatures.

HIGH TEMPERATURE SUPERCONDUCTIVITY AND BERRY PHASE

2003 ◽  
Vol 17 (03) ◽  
pp. 293-305 ◽  
Author(s):  
B. BASU ◽  
P. BANDYOPADHYAY ◽  
D. PAL
Keyword(s):  
High Temperature Superconductivity ◽  
Berry Phase ◽  
Renormalization Group Equation ◽  
Hole Doping ◽  
Group Equation ◽  
Spin Gap ◽  
Optimal Doping ◽  
Spin Pairing ◽  
Gap Phase ◽  
Universal Behaviour

We have analyzed the mechanism of high Tcsuperconductivity from the viewpoint of chirality and Berry phase. It is observed that spin pairing and charge pairing is caused by a gauge force generated by magnetic flux quanta attached to them. Different phase structures associated with high Tcsuperconductivity have been studied from an analysis of the renormalization group equation involving the Berry phase factor μ. It is found that there are two crossovers above the superconducting temperature Tc, one corresponding to the glass phase and the other represents spin gap phase. However, the spin gap temperature [Formula: see text] is found to be dependent on Tcand [Formula: see text] shows a universal behaviour with respect to the hole doping δ/δ0with δ0being the optimal doping rate.

Crystal Growth of High Temperature Superconductors

MRS Bulletin ◽  
1988 ◽  
Vol 13 (10) ◽  
pp. 56-61 ◽  
Author(s):  
H.J. Scheel ◽  
F. Licci
Keyword(s):  
High Temperature ◽  
Critical Current Density ◽  
Single Crystals ◽  
Critical Current ◽  
Current Density ◽  
Large Scale ◽  
High Temperature Superconductivity ◽  
High Temperature Superconductors ◽  
Superconducting Transition ◽  
Theoretical Understanding

The discovery of high temperature superconductivity (HTSC) in oxide compounds has confronted materials scientists with many challenging problems. These include the preparation of ceramic samples with critical current density of about 106 A/cm2 at 77 K and sufficient mechanical strength for large-scale electrotechnical and magnetic applications and the preparation of epitaxial thin films of high structural perfection for electronic devices.The main interest in the growth of single crystals is for the study of physical phenomena, which will help achieve a theoretical understanding of HTSC. Theorists still do not agree on the fundamental mechanisms of HTSC, and there is a need for good data on relatively defect-free materials in order to test the many models. In addition, the study of the role of defects like twins, grain boundaries, and dislocations in single crystals is important for understanding such parameters as the critical current density. The study of HTSC with single crystals is also expected to be helpful for finding optimum materials for the various applications and hopefully achieving higher values of the superconducting transition temperature Tc than the current maximum of about 125 K. It seems unlikely at present that single crystals will be used in commercial devices, but this possibility cannot be ruled out as crystal size and quality improve.

scholarly journals Photoinduced collective mode, inhomogeneity, and melting in a charge-order system

2018 ◽  
Vol 98 (23) ◽  
Author(s):  
Hitoshi Seo ◽  
Yasuhiro Tanaka ◽  
Sumio Ishihara
Keyword(s):  
Collective Mode ◽  
Charge Order ◽  
Order System ◽  
A Charge

scholarly journals Higher superconducting transition temperature by breaking the universal pressure relation

2019 ◽  
Vol 116 (6) ◽  
pp. 2004-2008 ◽  
Author(s):  
Liangzi Deng ◽  
Yongping Zheng ◽  
Zheng Wu ◽  
Shuyuan Huyan ◽  
Hung-Cheng Wu ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
High Temperature ◽  
Transition Temperature ◽  
Density Functional ◽  
High Temperature Superconductors ◽  
Density Functional Theory Calculations ◽  
Universal Relation ◽  
Superconducting Transition ◽  
Functional Theory ◽  
A Charge

By investigating the bulk superconducting state via dc magnetization measurements, we have discovered a common resurgence of the superconducting transition temperatures (Tcs) of the monolayer Bi2Sr2CuO6+δ(Bi2201) and bilayer Bi2Sr2CaCu2O8+δ(Bi2212) to beyond the maximum Tcs (Tc-maxs) predicted by the universal relation between Tcand doping (p) or pressure (P) at higher pressures. The Tcof underdoped Bi2201 initially increases from 9.6 K at ambient to a peak at 23 K at 26 GPa and then drops as expected from the universal Tc-P relation. However, at pressures above 40 GPa, Tcrises rapidly without any sign of saturation up to 30 K at 51 GPa. Similarly, the Tcfor the slightly overdoped Bi2212 increases after passing a broad valley between 20 and 36 GPa and reaches 90 K without any sign of saturation at 56 GPa. We have, therefore, attributed this Tcresurgence to a possible pressure-induced electronic transition in the cuprate compounds due to a charge transfer between the Cu 3dx2−y2and the O 2pbands projected from a hybrid bonding state, leading to an increase of the density of states at the Fermi level, in agreement with our density functional theory calculations. Similar Tc-P behavior has also been reported in the trilayer Br2Sr2Ca2Cu3O10+δ(Bi2223). These observations suggest that higher Tcs than those previously reported for the layered cuprate high-temperature superconductors can be achieved by breaking away from the universal Tc-P relation through the application of higher pressures.

scholarly journals Energy gap evolution across the superconductivity dome in single crystals of (Ba1−xKx)Fe2As2

2016 ◽  
Vol 2 (9) ◽  
pp. e1600807 ◽  
Author(s):  
Kyuil Cho ◽  
Marcin Kończykowski ◽  
Serafim Teknowijoyo ◽  
Makariy A. Tanatar ◽  
Yong Liu ◽  
...  
Keyword(s):  
Single Crystals ◽  
Abrupt Change ◽  
Energy Gap ◽  
Superconducting Transition ◽  
London Penetration Depth ◽  
Wave State ◽  
Iron Based Superconductors ◽  
Optimal Doping ◽  
Gap Anisotropy ◽  
Materials Research

The mechanism of unconventional superconductivity in iron-based superconductors (IBSs) is one of the most intriguing questions in current materials research. Among non-oxide IBSs, (Ba1−xKx)Fe2As2has been intensively studied because of its high superconducting transition temperature and fascinating evolution of the superconducting gap structure from being fully isotropic at optimal doping (x≈ 0.4) to becoming nodal atx> 0.8. Although this marked evolution was identified in several independent experiments, there are no details of the gap evolution to date because of the lack of high-quality single crystals covering the entire K-doping range of the superconducting dome. We conducted a systematic study of the London penetration depth, λ(T), across the full phase diagram for different concentrations of point-like defects introduced by 2.5-MeV electron irradiation. Fitting the low-temperature variation with the power law, Δλ ~Tn, we find that the exponentnis the highest and theTcsuppression rate with disorder is the smallest at optimal doping, and they evolve with doping being away from optimal, which is consistent with increasing gap anisotropy, including an abrupt change aroundx≃ 0.8, indicating the onset of nodal behavior. Our analysis using a self-consistentt-matrix approach suggests the ubiquitous and robust nature ofs±pairing in IBSs and argues against a previously suggested transition to ad-wave state nearx= 1 in this system.

scholarly journals Evolution of superconductivity and charge order in pressurized RbV3Sb5

2021 ◽  
Author(s):  
Feng Du ◽  
Shuaishuai Luo ◽  
Rui Li ◽  
Brenden R. Ortiz ◽  
Ye Chen ◽  
...  
Keyword(s):  
Normal State ◽  
Ambient Pressure ◽  
Charge Order ◽  
Superconducting Transition ◽  
Close Link ◽  
Pressure Medium ◽  
Similar Temperature ◽  
State Resistance ◽  
Pressure Phase ◽  
Normal State Resistance

Abstract The kagome metals AV3Sb5 (A = K, Rb, Cs) under ambient pressure exhibit an unusual charge order, from which superconductivity emerges. In this work, by applying hydrostatic pressure using a liquid pressure medium and carrying out electrical resistance measurements for RbV3Sb5, we find the charge order becomes suppressed under a modest pressure p c (1.4 < p c < 1.6 GPa), while the superconducting transition temperature T c is maximized. T c is then gradually weakened with further increase of pressure and reaches a minimum around 14.3 GPa, before exhibiting another maximum around 22.8 GPa, signifying the presence of a second superconducting dome. Distinct behaviors in the normal state resistance are found to be associated with the second superconducting dome, similar to KV3Sb5. Our findings point to qualitatively similar temperature-pressure phase diagrams in KV3Sb5 and RbV3Sb5, and suggest a close link between the second superconducting dome and the high-pressure normal state resistance.

scholarly journals Природа псевдощелевой фазы ВТСП купратов

2020 ◽  
Vol 62 (9) ◽  
pp. 1390
Author(s):  
А.С. Москвин ◽  
Ю.Д. Панов
Keyword(s):  
Density Wave ◽  
Charge Order ◽  
Lattice Relaxation ◽  
Field Approximation ◽  
Cuo2 Plane ◽  
Local Order ◽  
Effective Spin ◽  
Quantum Electron ◽  
A Charge ◽  
Quantum Antiferromagnet

The pseudogap phase of HTSC cuprates is associated with the formation of a system of quantum electron-hole (EH) dimers similar to the Anderson RVB-phase. We considered the specific role of electron-lattice relaxation in the formation of metastable EH dimers in cuprates with T- and T′-structures. In the model of charge triplets and S = 1 pseudospin formalism, the effective spin-pseudospin Hamiltonian of the cuprate CuO2 plane is introduced. In the framework of the molecular field approximation (MFA) for the coordinate representation, the main MFA phases were found: an antiferromagnetic insulator, a charge density wave, a bosonic superconductor with d-symmetry of the order parameter, and two metal Fermi-phases forming the phase of the "strange" metal. We argue that the MFA can correctly reproduce all the features of the typical cuprate phase diagrams. As for typical s = 1/2 quantum antiferromagnet the actually observed cuprate phases such as charge order and superconductivity reflect "physical" ground state, which is close to MFA-phases but with strongly reduced magnitudes of the local order parameters.

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