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P. Süle

Publications and source records attributed to P. Süle.

27 records · Page 2Linked to original sources
arXiv2004

Cooperative mixing induced surface roughening in bilayer metals: a possible novel surface damage mechanism

Molecular dynamics simulations have been used to study a collective atomic transport phenomenon by repeated Ar$^+$ irradiations in the Ti/Pt interfacial system. The ion-induced injection of surface atoms to the bulk, the ejection of bulk atoms to the top layers together with surface erosion is strongly enhanced by interfacial mixing. This process leads to a dense interfacial material, and broadening of the interface region. The process scales with the relative difference of the atomic masses. We find that surface roughening and interfacial mixing is strongly coupled via an enhanced counterflow material transport normal to the surface which might be a novel surface damage mechanism. This cooperative phenomenon is active when the bilayer system is subjected to a high dose ion irradiation (multiple ion irradiations) and leads to surface cavity growth.

cond-mat.mtrl-sci↗
arXiv2004

Possible three-dimensional chiral charge ordered superconducting state in cuprates

The 2D pair-condensate is characterized by a fluctuating chiral charge ordered state with a "checkerboard" pattern in the CuO_2 planes and with an alternating supermodulation along the c-axis in such a way that the adjacent layers are mirror images of one anothers electronic state. Planar chiral order is revealed with a recent circular dichroism (CD) ARPES experiment (A. Kaminski, et al., Nature, 416, 611. (2002)). We propose further CD experiments on ultrathin films with varying thickness and argue that the odd number of unit cells along the c-axis might provide dichroism hence might support the picture of 3D chirality in cuprates. We find that Coulomb energy gain occurs along the c-axis within a multilayer chiral charge ordered state, which is proportional to the measured bilayer condensation energy and to $T_c$ at optimal doping. Within our approach the superconducting (SC) pair is composed of the hole content of the coherence area and the self-repulsion of the condensate is compensated by the gain in the inter-layer Coulomb energy below $T_c$. The SC condensate and the fluctuating charge order can also be described by a dynamical inter-layer electrostatic complementarity.

cond-mat.supr-con↗
arXiv2003

The checkerboard modulation and the inter-layer asymmetry of the hole density in cuprates

The 2D pair-condensate is characterized by a charge ordered state with a "checkerboard" pattern in the planes and with an alternating superstructure along the c-axis.We find that Coulomb energy gain occurs along the c-axis, which is proportional to the measured condensation energy and is due to inter-layer charge complementarity (charge asymmetry of the boson condensate. The static c-axis dielectric constant and the in-plane coherence length are also calculated for various cuprates and compared with the available experimental data. We find excellent agreement .

cond-mat.supr-con↗
arXiv2003

Does the thermal spike affect low-energy ion-induced interfacial mixing?

Molecular dynamics simulations have been used to obtain the three-dimensional distribution of interfacial mixing and cascade defects in Ti/Pt multilayer system due to single 1 keV $Ar^+$ impacts at grazing angle of incidence. The Ti/Pt system was chosen because of its relatively high heat of mixing in the binary alloy and therefore a suitable candidate for testing the effect of heat of mixing on ion-beam mixing. However, the calculated mixing profile is not sensitive to the heat of mixing. Therefore the thermal spike model of mixing is not fully supported under these irradiation conditions. Instead we found that the majority of mixing occurs after the thermal spike during the relaxation process. These conclusions are supported by liquid, vacancy as well as adatom analysis. The interfacial mixing is in various aspects anomalous in this system: the time evolution of mixing is leading to a phase delay for Ti mixing, and Pt exhibits an unexpected double peaked mixing evolution. The reasons to these effects are discussed.

cond-mat.mtrl-sci↗
arXiv2003

Condensation energy, charge ordering and inter-layer coupling in cuprates

The correlation between the condensation energy and the critical temperature is studied within a charge ordered superlattice bilayer model in which pairing is supported by inter-layer Coulomb energy gain (potential energy driven superconductivity).The 2D pair-condensate can be characterized by a charge ordered state with a "checkerboard" like pattern seen by scanning tunneling microscopy.The drop of the c-axis dielectric screening can be the primary source of the condensation energy at optimal doping.We find that Coulomb energy gain occurs along the c-axis, which is proportional to the measured condensation energy ($U_0$) and to $T_c$: $E_c^{3D} \approx 2 (ξ_{ab}/a_0+1)^2 U_0 \approx k_B T_c$ and is due to inter-layer charge complementarity (charge asymmetry of the boson condensate)where $ξ_{ab}$ is the coherence length of the condensate and $a_0 \approx 3.9 Å$ is the in-plane lattice c onstant.The static c-axis dielectric constant $ε_c$ is calculated for various cuprates and compared with the available experimental data.

cond-mat.supr-con↗
arXiv2003

Charge ordering and inter-layer coupling in cuprates

We analyze the superconducting state and c-axis charge dynamics of cuprates at optimal doping using a charge ordered bilayer superlattice model in which pairing is supported by inter-layer Coulomb energy gain (potential energy driven superconductivity).The 2D pair-condensate can be characterized by a charge ordered state with a "checkerboard" like pattern seen by scanning tunneling microscopy.The pair condensation might lead to the sharp decrease of the normal state c-axis anisotropy of the hole content and hence to the decrease of inter-layer dielectric screening.The decrease of the c-axis dielectric screening can be the primary source of the condensation energy below $T_c$. We find that a net gain in the electrostatic energy occurs along the c-axis, which is proportional to the measured condensation energy ($U_0$) and with $T_c$:$E_c^{3D} \approx 2 (ξ_{ab}/a_0+1)^2 U_0 \approx k_B T_c$ and is due to inter-layer charge complementarity (charge asymmetry of the boson condensate) where $ξ_{ab}$ is the coherence length of the condensate and $a_0 \approx 3.9 Å$ is the in-planelattice constant.

cond-mat.supr-con↗
arXiv2002

Pair condensation and inter-layer coupling in cuprates: pairing on a superlattice

We analyze the superconducting state and the c-axis charge dynamics of cuprates using a charged ordered bilayer superlattice model in which pairing is supported by inter-layer Coulomb energy gain. The superlattice nature of high temperature superconductivity is experimentally suggested by the smallness of the coherent length ξ= 10 to 30 A which is comparable with a width of a 4X4 to 8X8 square supercell lattice layer. The temperature induced 2D-3D quantum phase transition of the hole-content is also studied. Pair condensation leads to the sharp decrease of the normal state c-axis anisotropy of the hole-content and reduces inter-layer dielectric screening. The decrease of the c-axis dielectric screening can be the primary source of the condensation energy. The 2D pair condensate can be characterized by a charge ordered state with a "checkboard" pattern seen by scanning tunneling microscopy.

cond-mat.supr-con↗
arXiv2001

Doping induced charge redistribution in the high temperature superconductor HgBa2CuO4

To understand the link between doping and electronic properties in high temperature superconductors, we report first-principles calculations on the oxygen doping effect for the single layer cuprate HgBa$_2$CuO$_{4+δ}$. The doping effect is studied both by supercell and single cell virtual crystal type approaches. We find ionic behavior of the dopant atom up to an optimal doping concentration of $δ=0.22$. The excess oxygen attracts electrons from the CuO$_2$ plane leading to an increase of the hole concentration in this building block. The maximum amount of holes is reached when the oxygen $p$-shell is nearly completely filled. As a consequence the density of states at the Fermi level exhibits a pronounced maximum at the optimal oxygen content. The calculated hole content as a function of doping is in accordance with experimental findings.

cond-mat.supr-con↗