arXiv subjects

Thomas A. Maier

Publications and source records attributed to Thomas A. Maier.

58 records · Page 4Linked to original sources

arXiv2011

Pressure induced renormalization of energy scales in the unconventional superconductor FeTe0.6Se0.4

We have carried out a pressure study of the unconventional superconductor FeTe0.6Se0.4 up to 1.5 GPa by neutron scattering, resistivity and magnetic susceptibility measurements. We have extracted the neutron spin resonance energy and the superconducting transition temperature as a function of applied pressure. Both increase with pressure up to a maximum at ~1.3 GPa. This analogous qualitative behavior is evidence for a correlation between these two fundamental parameters of unconventional superconductivity. However, Tc and the resonance energy do not scale linearly and thus a simple relationship between these energies does not exist even in a single sample. The renormalization of the resonance energy relative to the transition temperature is here attributed to an increased hybridization. The present results appear to be consistent with a pressure-induced weakening of the coupling strength associated with the fundamental pairing mechanism.

cond-mat.supr-con↗

arXiv2010

Microscopic Inhomogeneity and Superconducting Properties of a Two-dimensional Hubbard Model for High-$T_c$ Cuprate

Recent scanning tunneling microscopy measurements on cuprate superconductors have revealed remarkable spatial inhomogeneities in the single-particle energy gap. Using cellular dynamical mean-field theory, we study the zero temperature superconducting properties of a single-band Hubbard model with a spatial modulation of the electron density. We find that the inhomogeneity in the electronic structure results in a substantial spatial variation in the superconducting order parameter and single-particle energy gap, reminiscent of the experimental results. In particular, we find that the order parameter and gap amplitudes in the hole-rich regions are significantly enhanced over the corresponding quantities in a uniform system, if the hole-rich regions are embedded in regions with smaller hole density.

cond-mat.str-el↗

arXiv2009

Calculated Magnetic Exchange Interactions in High-Temeprature Superconductors

Using a first principles linear response approach, we study the magnetic exchange interactions J for a series of superconducting cuprates. We reproduce the observed spin-wave dispersions together with other experimental trends, and show that different cuprates have similar J's regardless their T$_{c}$. The nearest neighbor J is not sensitive to the hole-doping, which agrees with recent experiments. For the undoped cuprates, the second nearest neighbor J is ferromagnetic, but changes its sign with hole-doping. We also find that, in contrast to the hopping integral, the exchange interaction is not sensitive to the position of apical oxygen. To see the effect of the long--range nature of the exchange on the superconducting T$_{c}$, we study the dynamical spin susceptibility $χ(q,ω)$ within the t--J model using a dynamical cluster approximation.

cond-mat.str-el↗

arXiv2008

Enhanced Superconductivity in Superlattices of High-$T_c$ Cuprates

The electronic properties of multilayers of strongly correlated models for cuprate superconductors are investigated using cluster dynamical mean-field techniques. We focus on combinations of underdoped and overdoped layers and find that the superconducting order parameter in the overdoped layers is enhanced by the proximity effect of the strong pairing scale originating from the underdoped layers. The enhanced order parameter can even exceed the maximum value in uniform systems. This behavior is well reproduced in slave-boson mean-field calculations which also find higher transition temperatures than in the uniform system.

cond-mat.str-el↗