scholarly journals Reservoir Layers in High Tc Mercury Cuprates

1999 ◽  
Vol 574 ◽  
Author(s):  
T. H. Geballe ◽  
Boris Y. Moyzhes ◽  
P. H. Dicktnson
Keyword(s):  
Effective Mass ◽  
Cuprate Superconductors ◽  
Single Site ◽  
Pairing Interaction ◽  
High Tc ◽  
Wave Symmetry ◽  
Mercury Cuprates ◽  
Hg Cuprates ◽  
D Wave ◽  
Phase Differences

AbstractWe put forward the hypothesis that cations with 6s electrons (Hg,Tl,Pb,Bi) in the charge reservoir layers of high Tc cuprate superconductors actively participate in the pairing interaction as negative-U centers. We further argue that the Hg-cuprates are outstanding superconductors (Tc > 160 K) because they can exist as two-ion negative-U centers, . Their electrons are less localized than in single-site centers (negative-U or bipolaron) and can have a strong pairing interaction with a smaller increase in effective mass. The centers are oriented in the x and y directions and can have phase differences compatible with the d-wave symmetry of the CuO2 planes.

Effects of d-wave symmetry in high Tc step-edge Josephson junctions

2000 ◽  
Vol 341-348 ◽  
pp. 1473-1474 ◽  
Author(s):  
Soon-Gul Lee ◽  
Yunseok Hwang ◽  
Jin-Tae Kim ◽  
Gun Yong Sung
Keyword(s):  
Josephson Junctions ◽  
Step Edge ◽  
High Tc ◽  
Wave Symmetry ◽  
D Wave

On the Origin of Zero-Bias Conductance Peak in High-Tc Superconductors

1998 ◽  
Vol 12 (29n31) ◽  
pp. 3027-3030
Author(s):  
Alexander B. Nazarenko ◽  
Ernst A. Pashitskii ◽  
Alexander E. Pashitskii
Keyword(s):  
Elastic Scattering ◽  
Order Parameter ◽  
Magnetic Impurities ◽  
High Tc Superconductors ◽  
Zero Bias ◽  
High Tc ◽  
Conductance Peak ◽  
Wave Symmetry ◽  
Zero Bias Conductance ◽  
D Wave

We show that the zero-bias conductance peak observed in tunnel and point junctions of cuprates can be a consequence of "unitary" elastic scattering of the carriers by non-magnetic impurities in the vicinity of the junction interface and d-wave symmetry of the order parameter.

TUNNELING SPECTROSCOPY OF THE ELECTRON-DOPED CUPRATE SUPERCONDUCTOR Pr2-xCexCuO4

2002 ◽  
Vol 16 (20n22) ◽  
pp. 3175-3175
Author(s):  
A. BISWAS ◽  
P. FOURNIER ◽  
V. N. SMOLYANINOVA ◽  
H. BALCI ◽  
J. S. HIGGINS ◽  
...  
Keyword(s):  
Normal State ◽  
Cuprate Superconductors ◽  
Point Contact ◽  
Tunneling Spectroscopy ◽  
Pairing Symmetry ◽  
S Wave ◽  
Zero Bias ◽  
Wave Pairing ◽  
Wave Symmetry ◽  
D Wave

The properties of electron(n)-doped cuprate superconductors show significant deviations from those of their hold(p)-doped counterparts. Experiments prior to 2000 suggested an s-wave pairing symmetry as opposed to d-wave pairing symmetry in hole-doped cuprates. Recent experiments have suggested that n-doped cuprates have a d-wave pairing symmetry. However tunneling spectroscopy of these materials have not revealed a zero bias conductance peak (ZBCP), which is a classic signature of d-wave symmetry. We present the first tunneling spectroscopy data on n-doped Pr 2-x Ce x CuO 4 (PCCO) using point contact junctions which show a systematic evolution of the ZBCP. This method of junction fabrication is important as it allows the barrier strength between the normal and the superconducting electrodes to be varied. We show that this is essential to observing the ZBCP. The n-doped cuprates have a low Tc (~25 K ) and Hc2 (~10 T ). The low Hc2 enables us to obtain the normal state in PCCO at low temperatures. We have used this to probe the density of states in the normal state of PCCO. We observe an anomalous gap even in the normal state.1 This normal state gap (NSG) becomes smaller on the over-doped side. We discuss the behavior of this NSG in the context of the pseudogap which has been observed in hole-doped cuprates.

Pair Symmetry and Degree of Gap Depression at S-I Interfaces in HTS Josephson Junctions

1999 ◽  
Vol 13 (09n10) ◽  
pp. 1301-1306
Author(s):  
G. A. Ummarino ◽  
R. S. Gonnelli ◽  
C. Bravi ◽  
Masumi Inoue
Keyword(s):  
Josephson Junctions ◽  
Order Parameter ◽  
Reference Value ◽  
High Tc Superconductors ◽  
S Wave ◽  
General Reference ◽  
High Tc ◽  
Wave Symmetry ◽  
Set Up ◽  
D Wave

A new possible indirect way of testing pair symmetry in high-Tc superconductors has been set up. The degree of intrinsic gap depression at Superconductor-Insulator [S-I] interfaces required to match Ic(T)Rn(T) data in HTS Josephson junctions depends on the pair symmetry of the material itself, so that an higher fraction of d-wave symmetry for the order parameter requires less gap depression, while an higher fraction of s-wave corresponds to a larger degree of gap depression. In order to obtain a general reference value for the intrinsic amount of gap depression at S-I interfaces the de Gennes condition has been used, and resulting reduced Ic(T)Rn(T) data have been calculated in the framework of a mixed (s+id)-wave pair symmetry for the depressed order parameter ranging from pure s to pure d-wave. This model has been tentatively applied to two junctions' made of very different HTSs: YBCO and BKBO, yielding a result of almost pure d-wave for YBCO and of pure s-wave for BKBO.

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