Physics

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A brief overview is given of recent developments and fresh ideas at the intersection of PT-and/or CPT-symmetric quantum mechanics with supersymmetric quantum mechanics (SUSY QM). Within the framework of the resulting supersymmetric version of CPT-symmetric quantum mechanics we study the consequences of the assumption that the "charge" operator C is represented in a, differential-operator form of the second or higher order. Besides the freedom allowed by the Hermiticity constraint for the operator CP, encouraging results are obtained in the second-order case. In particular, the integrability of intertwining relations proves to match the closure of our nonlinear (viz., polynomial) SUSY algebra. In a particular illustration, our form of CPT-symmetric SUSY QM leads to a new class of non-Hermitian polynomial oscillators with real spectrum which turn out to be PT-asymmetric. © World Scientific Publishing Company.

(SoNS) School of Natural Sciences

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Fulltext

International Journal of Modern Physics A

CPT-conserving Hamiltonians and their nonlinear supersymmetrization using differential charge-operators C

Known shape-invariant potentials for the constant-mass Schrödinger equation are taken as effective potentials in a position-dependent effective mass (PDEM) one. The corresponding shape-invariance condition turns out to be deformed. Its solvability imposes the form of both the deformed superpotential and the PDEM. A lot of new exactly solvable potentials associated with a PDEM background are generated in this way. A novel and important condition restricting the existence of bound states whenever the PDEM vanishes at an end point of the interval is identified. In some cases, the bound-state spectrum results from a smooth deformation of that of the conventional shape-invariant potential used in the construction. In others, one observes a generation or suppression of bound states, depending on the mass-parameter values. The corresponding wavefunctions are given in terms of some deformed classical orthogonal polynomials. © 2005 IOP Publishing Ltd.

Journal of Physics A: Mathematical and General

Deformed shape invariance and exactly solvable Hamiltonians with position-dependent effective mass

In a box of size L, a spatially antisymmetric square-well potential of a purely imaginary strength ig and size l &lt; L is interpreted as an initial element of the SUSY hierarchy of solvable Hamiltonians, the energies of which are all real for g &lt; g c (l). The first partner potential is constructed in closed form and discussed.

Czechoslovak Journal of Physics

PT -supersymmetric partner of a short-range square well

The occurrence of a noncollinear magnetic structure at a Mn monolayer grown epitaxially on Fe(100) is predicted theoretically, using spinor density-functional theory and observed experimentally, using x-ray magnetic circular dichroism (XMCD) and linear dichroism (XMLD) spectroscopies. The combined use of XMCD and XMLD at the Mn-absorption edge allows us to assess the existence of ferromagnetic and antiferromagnetic order at the interface and also to determine the moment orientations with element specificity. The experimental results thus obtained are in excellent agreement with the magnetic structure determined theoretically. {\textcopyright} 2005 The American Physical Society.

Physical Review Letters

Spin-flop ordering from frustrated ferro- and antiferromagnetic interactions: A combined theoretical and experimental study of a Mn/Fe(100) monolayer

The structural and magnetic properties of dilutely doped 3d elements in pulsed laser deposition (PLD) grown HfO 2 high-k dielectric thin films were studied. Monoclinc phase of HfO 2 was stabilized by Co- and Fe- substitution at significantly low growth temperature. High purity HfO 2, CoO and Fe 2O 3 powders were mixed throughly in the required ratio for 5mol% Co and Fe doping in HfO 2. The results from atomic force microscopy showed possible segregation of Fe 3O 4 phase in the form of nanoscale mounds.

Materials Research Society Symposium Proceedings

Search for magnetism in Co and Fe-doped HfO 2 thin films for potential spintronic applications

A blue shifted photoluminescent emission in bis(2-(2′-hydroxyl phenyl)benzthiazolate)zinc (II) complex, ZBZT, arises out of the dimeric structure, typical of the localized electron density around the non-bridged ligand in the excited state of the complex. An average decay lifetime of 4.8 and 3.0 ns for the ligand and the complex, respectively indicates an energy transfer from the ligand to the metal. A PL quantum efficiency of about φ ZBZT=0.45 in DMF solution is observed, in comparison to the Alq 3, complex, φ Alq3=0.116. Semi empirical ZINDO/S-SCF-CI calculations support the dominance of non-bridged ligand moiety in controlling the photoluminescent properties. An unusually broad white light (FWHM ∼220 nm) electroluminescent emission in the two layer device structure brings out the features of an exciplex formation between the active layer ZBZT/TPD interface, which is studied at different current densities. Such a broadened emission is verified for different thicknesses of the active layer substantiating the role of exciplex formation. © 2004 Elsevier Ltd. All rights reserved.

Solid State Communications

Electroluminescent properties of dimeric bis(2-(2′-hydroxyl phenyl)benzthiazolate)zinc (II) complex

The relation between electrically active defects in organic and polymeric semiconductor materials and degradation of devices such as loss of luminance is currently not understood. In this paper, we study defect related charge processes using electrical transients in polymeric and organic diodes. We monitor slow charging and discharging currents as a function of time for both virgin and electrically aged devices. The current transients are analyzed spectroscopically in time domain using a technique called Time Analyzed Transient Spectroscopy, which is similar to DLTS in its implementation. We observe highly stretched exponentials over 3-4 orders of magnitude in time up to thousands of seconds indicating existence of large distribution in time constants in aged PLED devices. We demonstrate ability to distinguish between different mechanisms of charge storage related to defect related processes in typical OLED and PLED. © 2005 Materials Research Society.

Electrical transient based defect spectroscopy in polymeric and organic semiconductors

We have characterized the phase behavior of mixtures of the cationic surfactant cetyltrimethylammonium bromide (CTAB) and the organic salt 3-sodium-2-hydroxy naphthoate (SHN) over a wide range of surfactant concentrations using polarizing optical microscopy and X-ray diffraction. A variety of liquid crystalline phases, such as hexagonal, lamellar with and without curvature defects, and nematic, are observed in these mixtures. At high temperatures the curvature defects in the lamellar phase are annealed gradually on decreasing the water content. However, at lower temperatures these two lamellar structures are separated by an intermediate phase, where the bilayer defects appear to order into a lattice. The ternary phase diagram shows a high degree of symmetry about the line corresponding to equimolar CTAB/SHN composition, as in the case of mixtures of cationic and anionic surfactants. © 2005 American Chemical Society.

Langmuir

Phase behavior of concentrated aqueous solutions of cetyltrimethylammonium bromide (CTAB) and sodium hydroxy naphthoate (SHN)

In this paper, effects of lead doping on the lattice response and phase transitions of Sr1-xPbxBi2Nb2O 9 (x=0.0-0.5 in steps of 0.1) ferroelectric ceramics are reported. It is observed that structure attains more tetragonality with doping of lead up to 40%. Increased orthorhombic distortion is observed for undoped SEN and 50 at.% lead substituted SBN. Phase transitions for all samples were studied using Curie temperature measurements and are explained in terms of lattice response of these ceramics. Sample with x = 0.5 shows decreased tetragonal strain and Curie temperature. Relationship of polarization with lattice response is discussed. © 2004 Elsevier Ltd. All rights reserved.

Structural distortion and phase transition studies of Aurivillius type Sr1-xPbxBi2Nb2O9 ferroelectric ceramics

By using the point canonical transformation approach in a manner distinct from previous ones, we generate some new exactly solvable or quasi-exactly solvable potentials for the one-dimensional Schrödinger equation with a position-dependent effective mass. In the latter case, SUSYQM techniques provide us with some additional new potentials. © EDP Sciences.