arXiv subjects

Huaisong Zhao

Publications and source records attributed to Huaisong Zhao.

29 records · Page 2Linked to original sources

arXiv2016

Thermodynamic properties in triangular-lattice superconductors

The study of superconductivity arising from doping a Mott insulator has become a central issue in the area of superconductivity. Within the framework of the kinetic-energy-driven superconducting mechanism, we discuss the thermodynamic properties in triangular-lattice superconductors. It is shown that a sharp peak in the specific-heat appears at the superconducting transition temperature Tc, and then the specific-heat varies exponentially as a function of temperature for the temperatures T<Tc due to the absence of the d-wave gap nodes at the charge-carrier Fermi surface. In particular, the upper critical field follows qualitatively the charge-carrier pair gap type temperature dependence, and has the same dome-shaped doping dependence as Tc.

cond-mat.supr-con↗

arXiv2015

Electronic structure of cuprate superconductors in a full charge-spin recombination scheme

A long-standing unsolved problem is how a microscopic theory of superconductivity in cuprate superconductors based on the charge-spin separation can produce a large electron Fermi surface. Within the framework of the kinetic-energy driven superconducting mechanism, a full charge-spin recombination scheme is developed to fully recombine a charge carrier and a localized spin into a electron, and then is employed to study the electronic structure of cuprate superconductors in the superconducting-state. In particular, it is shown that the underlying electron Fermi surface fulfills Luttinger's theorem, while the superconducting coherence of the low-energy quasiparticle excitations is qualitatively described by the standard d-wave Bardeen-Cooper-Schrieffer formalism. The theory also shows that the observed peak-dip-hump structure in the electron spectrum and Fermi arc behavior in the underdoped regime are mainly caused by the strong energy and momentum dependence of the electron self-energy.

cond-mat.supr-con↗

arXiv2015

Kinetic-energy driven superconductivity in cuprate superconductors

Superconductivity in cuprate superconductors occurs upon charge-carrier doping Mott insulators, where a central question is what mechanism causes the loss of electrical resistance below the superconducting (SC) transition temperature? In this review, we attempt to summarize the basic idea of the kinetic-energy driven SC mechanism in the description of superconductivity in cuprate superconductors. The mechanism of the kinetic-energy driven superconductivity is purely electronic without phonons, where the charge-carrier pairing interaction arises directly from the kinetic energy by the exchange of spin excitations in the higher powers of the doping concentration. This kinetic-energy driven d-wave SC-state is controlled by both the SC gap and quasiparticle coherence, which leads to that the maximal SC transition temperature occurs around the optimal doping, and then decreases in both the underdoped and overdoped regimes. In particular, the same charge-carrier interaction mediated by spin excitations that induces the SC-state in the particle-particle channel also generates the normal-state pseudogap state in the particle-hole channel. The normal-state pseudogap crossover temperature is much larger than the SC transition temperature in the underdoped and optimally doped regimes, and then monotonically decreases upon the increase of doping, eventually disappearing together with superconductivity at the end of the SC dome. This kinetic-energy driven SC mechanism also indicates that the strong electron correlation favors superconductivity, since the main ingredient is identified into a charge-carrier pairing mechanism not from the external degree of freedom such as the phonon but rather solely from the internal spin degree of freedom of the electron. The typical properties of cuprate superconductors discussed within the framework of the kinetic-energy driven SC mechanism are also reviewed.

cond-mat.supr-con↗

arXiv2014

Pseudogap-induced asymmetric tunneling in cuprate superconductors

The asymmetric tunneling in cuprate superconductors is studied based on the kinetic energy driven superconducting mechanism. By taking into account the interplay between the superconducting gap and normal-state pseudogap, the essential feature of the evolution of the asymmetric tunneling with doping and temperature is qualitatively reproduced. In particular, the asymmetry of the tunneling spectrum in the underdoped regime weakens with increasing doping, and then the symmetric tunneling spectrum recovers in the heavily overdoped regime. The theory also shows that the asymmetric tunneling is a natural consequence due to the presence of the normal-state pseudogap.

cond-mat.supr-con↗

arXiv2012

Why there is a difference between optimal doping for maximal Tc and critical doping for highest ρ_s in cuprate superconductors?

A long-standing puzzle is why there is a difference between the optimal doping δ_{optimal}=0.15 for the maximal superconducting (SC) transition temperature Tc and the critical doping δ_{critical}=0.19 for the highest superfluid density ρ_s in cuprate superconductors? This puzzle is calling for an explanation. Within the kinetic energy driven SC mechanism, it is shown that except the quasiparticle coherence, ρ_s is dominated by the bare pair gap, while Tc is set by the effective pair gap. By calculation of the ratio of the effective and the bare pair gaps, it is shown that the coupling strength decreases with increasing doping. This doping dependence of the coupling strength induces a shift from the critical doping for the maximal value of the bare pair gap parameter to the optimal doping for the maximal value of the effective pair gap parameter, which leads to a difference between the optimal doping for the maximal Tc and the critical doping for the highest ρ_s.

cond-mat.supr-con↗

arXiv2012

Pseudogap and its connection to particle-hole asymmetry electronic state and Fermi arcs in cuprate superconductors

The particle-hole asymmetry electronic state of cuprate superconductors and the related doping and temperature dependence of the Fermi arc length are studied based on the kinetic energy driven superconducting mechanism. By taking into account the interplay between the SC gap and normal-state pseudogap, the essential feature of the evolution of the Fermi arc length with doping and temperature is qualitatively reproduced. It is shown that the particle-hole asymmetry electronic state is a natural consequence due to the presence the normal-state pseudogap in the particle-hole channel. The Fermi arc length increases with increasing temperatures below the normal-state pseudogap crossover temperature $T^{*}$, and it covers the full length of the Fermi surface for $T>T^{*}$. In particular, in analogy to the temperature dependence of the Fermi arc length, the low-temperature Fermi arc length in the underdoped regime increases with increasing doping, and then it evolves into a continuous contour in momentum space near the end of the superconducting dome. The theory also predicts an almost linear doping dependence of the Fermi arc length.

cond-mat.supr-con↗

arXiv2012

Doping dependence of electromagnetic response in electron-doped cuprate superconductors

Within the framework of the kinetic energy driven superconducting mechanism, the doping dependence of the electromagnetic response in the electron-doped cuprate superconductors is studied. It is shown that although there is an electron-hole asymmetry in the phase diagram, the electromagnetic response in the electron-doped cuprate superconductors is similar to that observed in the hole-doped cuprate superconductors. The superfluid density depends linearly on temperature, except for the strong deviation from the linear characteristics at the extremely low temperatures.

cond-mat.supr-con↗

arXiv2012

Doping dependence of thermodynamic properties in cuprate superconductors

The doping and temperature dependence of the thermodynamic properties in cuprate superconductors is studied based on the kinetic energy driven superconducting mechanism. By considering the interplay between the superconducting gap and normal-state pseudogap, the some main features of the doping and temperature dependence of the specific-heat, the condensation energy, and the upper critical field are well reproduced. In particular, it is shown that in analogy to the domelike shape of the doping dependence of the superconducting transition temperature, the maximal upper critical field occurs around the optimal doping, and then decreases in both underdoped and overdoped regimes. Our results also show that the humplike anomaly of the specific-heat near superconducting transition temperature in the underdoped regime can be attributed to the emergence of the normal-state pseudogap in cuprate superconductors.

cond-mat.supr-con↗

arXiv2012

Two gaps with one energy scale in cuprate superconductors

The interplay between the superconducting gap and normal-state pseudogap in cuprate superconductors is studied based on the kinetic energy driven superconducting mechanism. It is shown that the interaction between charge carriers and spins directly from the kinetic energy by exchanging spin excitations in the higher power of the doping concentration induces the normal-state pseudogap state in the particle-hole channel and superconducting state in the particle-particle channel, therefore there is a coexistence of the superconducting gap and normal-state pseudogap in the whole superconducting dome. This normal-state pseudogap is closely related to the quasiparticle coherent weight, and is a necessary ingredient for superconductivity in cuprate superconductors. In particular, both the normal-state pseudogap and superconducting gap are dominated by one energy scale, and they are the result of the strong electron correlation.

cond-mat.supr-con↗

arXiv2011

Magnetic field induced reduction of the low-temperature superfluid density in cuprate superconductors

The weak magnetic field induced reduction of the low-temperature superfluid density in cuprate superconductors is studied based on the kinetic energy driven superconducting mechanism. The electromagnetic response kernel is evaluated by considering both couplings of the electron charge and electron magnetic momentum with a weak magnetic field and employed to calculate the superfluid density, then the main features of the weak magnetic field induced reduction of the low-temperature superfluid density are well reproduced. The theory also shows that the striking behavior of the weak magnetic field induced reduction of the low-temperature superfluid density is intriguingly related to both depairing due to the Pauli spin polarization and nonlocal response in the vicinity of the d-wave gap nodes on the Fermi surface to a weak magnetic field.

cond-mat.supr-con↗

arXiv2010

Doping dependence of Meissner effect in cuprate superconductors

Within the t-t'-J model, the doping dependence of the Meissner effect in cuprate superconductors is studied based on the kinetic energy driven superconducting mechanism. Following the linear response theory, it is shown that the electromagnetic response consists of two parts, the diamagnetic current and the paramagnetic current, which exactly cancels the diamagnetic term in the normal state, and then the Meissner effect is obtained for all the temperature $T\leq T_{c}$ throughout the superconducting dome. By considering the two-dimensional geometry of cuprate superconductors within the specular reflection model, the main features of the doping and temperature dependence of the local magnetic field profile, the magnetic field penetration depth, and the superfluid density observed on cuprate superconductors are well reproduced. In particular, it is shown that in analogy to the domelike shape of the doping dependent superconducting transition temperature, the maximal superfluid density occurs around the critical doping $δ\approx 0.195$, and then decreases in both lower doped and higher doped regimes.

cond-mat.supr-con↗