Spin–charge gauge compositeness of electron in HTS: Hints from metal–insulator crossover and entropy behavior

Marchetti, P. A.; Ambrosetti, Achille; Su, Zhixun; Yu, L.

doi:10.1016/j.jpcs.2008.06.066

Cited by 2 publications

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References 28 publications

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“…We propose a new, non-BCS mechanism of superconductivity (SC) for hole-underdoped cuprates relying in essential way upon a "compositeness" [1] of the low-energy hole excitation appearing in the spin-charge gauge approach [2] to the 2D t-J model, used to describe the CuO planes. This "composite" structure involves a gapful bosonic constituent carrying spin 1/2 (spinon z α ) and a gapless spinless fermionic constituent carrying charge (holon h), supported on the empty sites.…”

Section: Introductionmentioning

confidence: 99%

Non-BCS superconductivity for underdoped cuprates by spin-vortex attraction

Marchetti

et al. 2011

Journal of Physics and Chemistry of Solids

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Within a gauge approach to the t-J model, we propose a new, non-BCS mechanism of superconductivity for underdoped cuprates. The gluing force of the superconducting mechanism is an attraction between spin vortices on two different N\'eel sublattices, centered around the empty sites described in terms of fermionic holons. The spin fluctuations are described by bosonic spinons with a gap generated by the spin vortices. Due to the no-double occupation constraint, there is a gauge attraction between holon and spinon binding them into a physical hole. Through gauge interaction the spin vortex attraction induces the formation of spin-singlet (RVB) spin pairs with a owering of the spinon gap. Lowering the temperature the approach exhibits two crossover temperatures: at the higher crossover a finite density of incoherent holon pairs are formed leading to a reduction of the hole spectral weight, at the lower crossover also a finite density of incoherent spinon RVB pairs are formed, giving rise to a gas of incoherent preformed hole pairs, and magnetic vortices appear in the plasma phase. Finally, at a even lower temperature the hole pairs become coherent, the magnetic vortices become dilute and superconductivity appears. The superconducting mechanism is not of BCS-type since it involves a gain in kinetic energy (for spinons) coming from the spin interactions

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Section: Introductionmentioning

confidence: 99%

Non-BCS superconductivity for underdoped cuprates by spin-vortex attraction

Marchetti

et al. 2011

Journal of Physics and Chemistry of Solids

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Superfluid Density in Cuprates: Hints on Gauge Compositeness of the Holes

Marchetti

Bighin

2016

J Supercond Nov Magn

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Abstract. We show that several features (the three-dimensional XY universality for moderate underdoping, the almost-BCS behaviour for moderate overdoping and the critical exponent) of the superfluid density in hole-doped cuprates hint at a composite structure of the holes. This idea can be implemented in a spin-charge gauge approach to the t − t − J model and provides indeed good agreement with available experimental data. Superfluid density: a puzzle and a solutionIn this work we point out some features of the in-plane superfluid density ρ s in hole-doped high-T c cuprates which hint at, or at least are fully compatible with, a peculiar "gauge compositeness" of the low-energy hole excitations in such materials. A similar suggestion comes also from transport and entropy arguments as discussed in Ref.[1]. Superfluid density in underdoped cuprates: theoretical constraints from experiments.In the region from moderate underdoping to optimal doping the superfluid density as a function of the temperature ρ s (T ) exhibits a linear T -dependence near T = 0, along with the critical exponent 2 /3 at the critical temperature T c [2]. In the same doping region, the normalized superfluid density ρ s (T /T c )/ρ s (0) shows a non-BCS, 3DXY-like universality independent both of doping concentration and of the specific kind of material involved [3,4]. Finally, the Uemura linear relation [5] between ρ s (T = 0) and T c approximately holds in underdoped cuprates.These features put severe constraints on theoretical explanations of the behaviour of ρ s . Specifically a BCS-based explanation of the T -linear dependence at low temperatures, as due to the quasi-particle excitations near the nodes of the d-wave BCS order parameter [6], is difficult to reconcile with the non mean-field critical exponent (which should be 1 according to the BCS theory), with the observed universality and with the Uemura relation, as within the BCS theory ρ s (0) does not depend on the order parameter controlling T c .An alternative explanation of the T -linear behaviour is based on phase or pairing fluctuations [7] of the order parameter in a BCS-BEC crossover setting, resulting in an effective low-energy XY model. However the most natural XY model obtained is two-dimensional, thus producing an incorrect critical behaviour. A three-dimensional nature of the XY model is sometimes claimed to emerge in a narrow range of temperatures close to T c due to the presence of a stack of Cu-O layers, but this is not sufficient to explain the three-dimensional XY universality of the normalized ρ s over the entire temperature range from T = 0 to T c . Furthermore, a well defined arXiv:1607.03801v1 [cond-mat.supr-con]

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Spin–charge gauge compositeness of electron in HTS: Hints from metal–insulator crossover and entropy behavior

Abstract: . Spin-charge gauge compositeness of electron in HTS: Hints from metal-insulator crossover and entropy behavior.

Cited by 2 publications

References 28 publications

Non-BCS superconductivity for underdoped cuprates by spin-vortex attraction

Non-BCS superconductivity for underdoped cuprates by spin-vortex attraction

Superfluid Density in Cuprates: Hints on Gauge Compositeness of the Holes

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