Physics

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We construct an isospectrum system in terms of a real and a complex potential to show that the underlying PT-symmetric complex Hamiltonian possesses a real spectrum which is shared by its real partner.

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Journal of Physics A: Mathematical and General

A new PT-symmetric complex Hamiltonian with a real spectrum

The family of complex PT-symmetric sextic potentials is studied to show that for various cases the system is essentially quasi-solvable and possesses real, discrete energy eigenvalues. For a particular choice of parameters, we find that under supersymmetric transformations the underlying potential picks up a reflectionless part. (C) 2000 Elsevier Science B.V.

Physics Letters, Section A: General, Atomic and Solid State Physics

PT-symmetric sextic potentials

Modern Physics Letters A

Erratum: Higher derivative supersymmetry, a modified crum-darboux transformation and coherent state (Modern Physics Letters A (1999) 14.1 (27-34))

A new model of supersymmetry between bosons and fermions is proposed. Its representation space is spanned by states with PT symmetry and real energies but the inter-related partner Hamiltonians themselves remain complex and non-Hermitian. The formalism admits vanishing Witten index. (C) 2000 Elsevier Science B.V.

Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

Supersymmetry without hermiticity within PT symmetric quantum mechanics

Thin Ta layers deposited on Si (100) substrates were irradiated with 475 keV Xe+ ions to fluences of (0.5-2) x 1016 ions/cm2 at temperatures between room temperature and 400 °C. By means of Rutherford Backscattering Spectrometry, the interface mixing and tantalum silicide formation were monitored as function of the ion fluence. TaSi2 phase formation was verified using X-ray diffraction. The interface broadening variance was found to depend linearly on the ion fluence and was explained with the help of a compound formation model involving global thermal spikes.

Physica Status Solidi (B) Basic Research

Mixing and silicide formation during Xe-Ion beam irradiations of Ta/Si bilayers

Nitrides, carbides and oxides are important ceramic materials for wide range of applications in coating, nuclear reactor and semiconductor technology. The study of their bonding properties to metals and semiconductors, for instance via ion irradiation, is of great importance. In this work, we report on the effects induced by 100 and 450 keV Xe+ ions in 70-100 nm Ni3N layers deposited on Si substrates. Low-energy irradiation at 80 K was found to cause a preferential nitrogen loss in the near-surface regions and an increase in surface roughness of the Ni3N film. After the 450 keV Xe+ ion irradiation, strong mixing and the formation of Ni2Si and Si3N4 phases were detected at the Ni3N/Si interface. These findings demonstrate the dissociation of Ni3N under ion bombardment and the competition of chemical driving forces and collision cascade mixing at the interface.

Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms

Ion-beam irradiation effects on Ni3N/Si bilayers

We report on the room-temperature synthesis of the low-resistivity TaSi2 phase using ion-beam mixing of Ta/Si bilayers with Ar ions. The formation of the silicide phase is observed for different damage energies deposited at the Ta/Si interface. The variance Δσ2 of the reacted (TaSi2) layer thickness varies linearly with the ion fluence Φ and the reaction rate Δσ2/Φ is proportional to the deposited damage energy density FD. The measured mixing/reaction efficiency, Δσ2/ΦFD = 10 ± 1 nm5/keV, is in agreement with the value calculated by the model of compound formation under local thermal spikes.

Interface mixing in Ta/Si bilayers with Ar ions

The migration of oxygen in ion-beam-amorphized c-SiO2 (α-quartz) was investigated by means of nuclear reaction analysis using the resonant reaction 18O(p, α) 15N for oxygen depth profiling. Only very small amounts of oxygen were observed to diffuse in crystalline or in Xe+-ion beam-amorphized α-quartz after high-temperature annealing. However, a dramatic migration of oxygen occurs in Cs+-implanted α-quartz in the same temperature range (600-900°C), where Cs diffuses out of the amorphized layer and epitaxial recrystallization occurs. These results point out to a strong correlation of all these processes. A mechanism to explain the observed indiffusion of 18O is proposed and is related to the Cs migration and the topological modification to achieve epitaxial regrowth of the SiO2 matrix. © 2000 American Institute of Physics.

Applied Physics Letters

Oxygen migration during epitaxial regrowth in Cs+-irradiated α-quartz investigated by means of nuclear reaction analysis

We study two-mode squeezing in the framework of generalized quantum condition and derive pedagogically the result that the two-mode squeezed state is factorizable in terms of the component single modes. We also examine the related problem of two-mode squeezing in the system of a pair of coupled oscillators and consider the effects of a sudden switching-on of the intermode coupling for these quadrature modes.

A reappraisal of two-mode squeezing and intermode coupling

The powerful group theoretical formalism of potential algebras is extended to non-Hermitian Hamiltonians with real eigenvalues by complexifying so(2,1), thereby getting the complex algebra s1(2,C) or A1. This leads to new types of both PT-symmetric and non-PT-symmetric Hamiltonians. (C) 2000 Elsevier Science B.V.