Raman spectrum in the pseudogap phase of the underdoped cuprates: effect of phase coherence and the signature of the KT-type superconducting transition

2011 ◽  
Vol 23 (46) ◽  
pp. 464201
Author(s):  
Tao Li ◽  
Haijun Liao
Keyword(s):  
Raman Spectrum ◽  
Phase Coherence ◽  
Superconducting Transition ◽  
Pseudogap Phase ◽  
Underdoped Cuprates

scholarly journals INTERPLAY OF D-WAVE SUPERCONDUCTIVITY AND ANTIFERROMAGNETISM IN THE CUPRATE SUPERCONDUCTORS: PHASE SEPARATION AND THE PSEUDOGAP PHASE DIAGRAM

2005 ◽  
Vol 19 (25) ◽  
pp. 1295-1302 ◽  
Author(s):  
W. P. SU
Keyword(s):  
Phase Diagram ◽  
Phase Separation ◽  
Cuprate Superconductors ◽  
Nearest Neighbor ◽  
Superconducting Transition ◽  
Zero Temperature ◽  
Pseudogap Phase ◽  
Underdoped Cuprates ◽  
D Wave ◽  
Interaction Free Energy

To understand the interplay of d-wave superconductivity and antiferromagnetism in the cuprates, we consider a two-dimensional extended Hubbard model with nearest neighbor attractive interaction. Free energy of the homogeneous (coexisting superconducting and antiferromagnetic) state calculated as a function of the band filling shows a region of phase separation. The phase separation caused by the intersite attractive force leads to novel insights into salient features of the pseudogap phase diagram. In particular, the upper crossover curve can be identified with the phase separation boundary. At zero temperature, the boundary constitutes a critical point. The inhomogeneity observed in the underdoped cuprates is a consequence of incomplete phase separation. The disorder (inhomogeneity) brings about the disparity between the high pseudogap temperature and the low bulk superconducting transition temperature.

scholarly journals Translation-Invariant Bipolarons and Charge Density Waves in High-Temperature Superconductors

2021 ◽  
Vol 9 ◽  
Author(s):  
Victor D. Lakhno
Keyword(s):  
Charge Density ◽  
High Temperature Superconductors ◽  
Bose Condensate ◽  
Density Wave ◽  
Charge Density Waves ◽  
Superconducting Transition ◽  
Density Waves ◽  
Translation Invariant ◽  
Pseudogap Phase ◽  
Pair Density

A correlation is established between the theories of superconductivity based on the concept of charge density waves (CDWs) and the translation invariant (TI) bipolaron theory. It is shown that CDWs are originated from TI-bipolaron states in the pseudogap phase due to the Kohn anomaly and form a pair density wave (PDW) for wave vectors corresponding to nesting. Emerging in the pseudogap phase, CDWs coexist with superconductivity at temperatures below those of superconducting transition, while their wave amplitudes decrease as a Bose condensate is formed from TI bipolarons, vanishing at zero temperature.

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.

Investigation of Fluctuating Diamagnetism and Spin Dynamics in SmFeAsO1-xFx Superconductors

2010 ◽  
Vol 75 ◽  
pp. 141-146 ◽  
Author(s):  
Giacomo Prando ◽  
Pietro Carretta ◽  
Alessandro Lascialfari ◽  
Attilio Rigamonti ◽  
Samuele Sanna ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Nmr Spectroscopy ◽  
Superconducting Transition Temperature ◽  
Spin Dynamics ◽  
Magnetic Coupling ◽  
Iron Pnictides ◽  
Superconducting Transition ◽  
Squid Magnetometry ◽  
Conduction Electrons ◽  
Underdoped Cuprates

The superconducting iron-pnictides SmFeAsO1-xFx (x = 0.15 and x = 0.2) are studied by means of 19F-NMR spectroscopy and SQUID magnetometry. Fluctuating diamagnetism above Tc is briefly examined, stressing the analogy with the phenomenology in underdoped cuprates. The 19F relaxation rate allows us to infer an indirect magnetic coupling between Sm3+ moments, possibly involving conduction electrons in FeAs bands, with no appreciable effects on crossing the superconducting transition temperature. A comparison between the superconducting samples and the insulating SmOF, often present as spurious phase in SmFeAsO1-xFx pnictides, is also carried out. Relevant differences in the spin dynamics features are found.

scholarly journals Magnetism and Superconductivity in the Pseudogap Phase of Underdoped Cuprates

2013 ◽  
Vol 449 ◽  
pp. 012006 ◽  
Author(s):  
A J A James ◽  
R M Konik ◽  
K Huang ◽  
W-Q Chen ◽  
T M Rice ◽  
...  
Keyword(s):  
Pseudogap Phase ◽  
Underdoped Cuprates

scholarly journals Fluctuations and the Higgs Mechanism in Underdoped Cuprates

2020 ◽  
Vol 11 (1) ◽  
pp. 301-323 ◽  
Author(s):  
C. Pépin ◽  
D. Chakraborty ◽  
M. Grandadam ◽  
S. Sarkar
Keyword(s):  
High Temperature ◽  
Cuprate Superconductors ◽  
High Temperature Superconductivity ◽  
Higgs Mechanism ◽  
Pseudogap Phase ◽  
Theoretical Approaches ◽  
Underdoped Region ◽  
Underdoped Cuprates ◽  
The Rich ◽  
Ubiquitous Presence

The physics of the pseudogap phase of high-temperature cuprate superconductors has been an enduring mystery over the past 30 years. The ubiquitous presence of the pseudogap phase in underdoped cuprates suggests that understanding it is key to unraveling the origin of high-temperature superconductivity. We review various theoretical approaches to this problem, emphasizing the concept of emergent symmetries in the underdoped region of those compounds. We differentiate these theories by considering a few fundamental questions related to the rich phenomenology of these materials. Lastly, we discuss a recent idea regarding two kinds of entangled preformed pairs that open a gap at the pseudogap onset temperature, T*, through a specific Higgs mechanism. We review the experimental consequences of this line of thought.

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