Effect Of Nonmagnetic Disorder Research Articles

The effect of nonmagnetic disorder on phase transitions of the first-order

The effect of nonmagnetic disorder on phase transitions of the first-order

The effect of nonmagnetic disorder in the superconducting energy gap of strontium ruthenate

We have performed for the strontium ruthenate compound, a disordered tight-binding numerical study in the unitary and intermedia scattering regimes analyzing the imaginary part of the self-consistent elastic scattering cross-section at zero temperature as a function of the superconducting gap parameter using the anisotropic limit of the γ sheet. We start this research, mentioning a set of different zero energy superconducting spectrum values inferred from experimental data. Furthermore, it is reproduced the Miyake–Narikiyo tiny triplet gap by varying the zero energy superconducting microscopic parameter. Additionally, using the finite temperature Matsubara Green functions formalism, it is investigated the energy gap as a function temperature and disorder. We conclude that the evolution of the reduced phase space using the elastic scattering cross-section for a triplet order parameter is a useful numerical technique and predicts the two elastic scattering regimes for strontium ruthenate.

The Effect of Nonmagnetic Disorder in the Energy Gap at Zero Temperature for the Fs Γ-Sheet of Strontium Ruthenate

The Effect of Nonmagnetic Disorder in the Energy Gap at Zero Temperature for the Fs Γ-Sheet of Strontium Ruthenate

Effects of nonmagnetic disorder on the energy of Yu-Shiba-Rusinov states

We study the sensitivity of Yu-Shiba-Rusinov states, bound states that form around magnetic scatterers in superconductors, to the presence of nonmagnetic disorder in both two and three dimensional systems. We formulate a scattering approach to this problem and reduce the effects of disorder to two contributions: disorder-induced normal reflection and a random phase of the amplitude for Andreev reflection. We find that both of these are small even for moderate amounts of disorder. In the dirty limit in which the disorder-induced mean free path is smaller than the superconducting coherence length, the variance of the energy of the Yu-Shiba-Rusinov state remains small in the ratio of the Fermi wavelength and the mean free path. This effect is more pronounced in three dimensions, where only impurities within a few Fermi wavelengths of the magnetic scatterer contribute. In two dimensions the energy variance is larger by a logarithmic factor because impurities contribute up to a distance of the order of the superconducting coherence length.

Edge States in a Thin Film of Disordered Topological Insulator

A thin-film geometry of nonmagnetic or magnetic topological insulator (TI) alters its topological properties depending on the thickness of the film and the strength of the magnetic coupling, and can exhibit the quantum spin Hall (QSH) effect as well as the quantum anomalous Hall (QAH) effect. In this study, we pursue a quantitative investigation of effects of nonmagnetic disorder on thin-film TIs in all the possible topological phases. The results show that strong enough disorder induces a topological phase transition and generically creates metallic helical edge states featuring the QSH phase before all electronic states are eventually localized. In the thermodynamic limit, the localization–delocalization transition in the disorder-induced QSH phase is in the unitary universality class with nontrivial Chern numbers. In a finite-size system, topologically protected edge states persist unless the mobility gap collapses. It is also demonstrated that edge states extend over a macroscopic distance in the midd...

Topological superconductivity and Majorana bound states at the LaAlO3/SrTiO3 interface

The interface between two band insulators LaAlO3 and SrTiO3 exhibits low-temperature superconductivity coexisting with an in-plane ferromagnetic order. We show that topological superconductivity hosting Majorana bound states can be induced at the interface by applying a magnetic field perpendicular to the interface. We find that the dephasing effect of the in-plane magnetization on the topological superconducting state can be overcome by tuning a gate voltage. We analyze the vortex-core excitations showing the zero-energy Majorana bound states and the effect of non-magnetic disorder on them. Finally, we propose an experimental geometry where such topological excitations can be realized.

Kosterlitz-Thouless Transition: The Diluted XY model

The effect of nonmagnetic disorder on Berezinskii-Kosterlitz-Thouless (BKT) transition in the two-dimensional ferromagnetic XY model on a square lattice, diluted by randomly placed vacancies can be an important source of information on the role played by vortexes in this transition. The transition temperature TBKT is determined as a function of vacancy density ρv by stiffness ρ and for different size of the lattice. The anomalous behavior for TBKT when ρv is close to the square lattice percolation limit is a consequence of the effect of finite size of lattice and not due the quantum fluctuations as concluded in literature. We obtain that TBKT falls to zero at ρv ≈ 0.40 close to the value 0.41 obtained for the classic model.

Effects of randomness on the critical temperature in quasi-two-dimensional organic superconductors

The effects of nonmagnetic disorder on the critical temperature ${T}_{c}$ of organic weak-linked layered superconductors with singlet in-plane pairing are considered. A randomness in the interlayer Josephson coupling is shown to destroy phase coherence between the layers, and ${T}_{c}$ suppresses smoothly in a large extent of the disorder strength. Nevertheless, the disorder of arbitrarily high strength cannot destroy completely the superconducting phase. The obtained quasilinear decrease of the critical temperature with increasing disorder strength is in good agreement with experimental measurements.

Disorder-driven superconductor–normal metal phase transition in quasi-one-dimensional organic conductors

Effects of nonmagnetic disorder on the critical temperature ${T}_{c}$ and on diamagnetism of quasi-one-dimensional superconductors are reported. The energy of Josephson coupling between wires is considered to be random, which is typical for dirty organic superconductors. We show that this randomness destroys phase coherence between wires and that ${T}_{c}$ vanishes discontinuously at a critical disorder strength. The parallel and transverse components of the penetration depth are evaluated. They diverge at different critical temperatures ${T}_{c}^{(1)}$ and ${T}_{c}$, which correspond to pair breaking and phase-coherence breaking, respectively. The interplay between disorder and quantum phase fluctuations is shown to result in quantum-critical behavior at $T=0$, which manifests itself as a superconducting normal metal phase transition of first order at a critical disorder strength.

SPATIAL FLUCTUATIONS OF THE ORDER PARAMETER IN A DISORDERED SUPERCONDUCTOR WITH p-WAVE PAIRING

The effect of nonmagnetic disorder on the pairing amplitude is studied by means of a perturbation method. Using an extended one band Hubbard model with an intersite attraction we analyze various solutions of p-wave pairing symmetry and discuss their instability calculating fluctuations of order parameter. The model is applied to describe the effect of disorder in Sr2RuO4. The results shows that the real solution with line nodes can be favoured by disorder.