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Bridgman tekniği ile büyütülen saf, % 0.1 ve % 0.5 bor katkılı InSe tek kristallerinin morfolojik ve optik soğurma özellikleri araştırıldı. Saf, % 0.1 ve % 0.5 bor katkılı InSe tek kristallerinin morfolojik ve optik soğurma özellikleri AFM, SEM ve UV-Vis spektrofotometre teknikleri ile araştırıldı. SEM analizleri geniş yüzeyli yüksek kalitede InSe tek kristallerinin stokiyometrik eriyikten büyüdüğünü gösterdi. Optik soğurma spektrumlarının analizinden saf ve % 0.1 bor katkılı InSe tek kristallerine oranla % 0.5 bor katkılı InSe tek kristalinin eksiton pikinin genişlediği görüldü. Ayrıca, bor katkısı sonucu soğurma şiddetinin azaldığı ve soğurma kenarının daha uzun dalga boyuna doğru kaydığı görüldü. Optik soğurma ölçümlerinden, hem saf hem de bor katkılı InSe tek kristallerinin direkt yasak enerji bant aralığına sahip olduğu gözlendi. Ayrıca, saf InSe tek kristalinin yasak enerji bant aralığına oranla bor katkılı InSe tek kristallerinin yasak enerji bant aralıklarının katkı oranına bağlı olarak azaldığı görüldü., Morphological and optical absorption properties of undoped, 0.1 at% and 0.5 at% boron doped InSe single crystals grown by Bridgman technique were investigated. Morphological and optical absorption properties of undoped, 0.1 at% and 0.5 at% boron doped InSe single crystals have been investigated by AFM, SEM and UV-Vis spectrophotometer techniques. SEM analysis showed that high quality InSe single crystals with large surface area were grown from the stoichiometric melt. From the analysis of optical absorption spectra showed that the exciton peak in 0.5 at% boron doped InSe single crystal expanded by relative to the undoped and 0.1 at% boron doped InSe single crystals. In addition, it was seen that the intensity of absorption decreased and absorption edge shifted to longer wavelengths as a result of boron doping. Optical absorption measurements showed that both undoped and boron doped InSe single crystals had direct forbidden band energies. Also, energy band gaps in boron doped InSe single crystals decreased with increasing boron concentration relative to the energy band gap of undoped InSe single crystal.

Bu tez çalısmasında yönlendirilebilir Riemann manifoldları üzerinde bilinen Spincspinor teorisine benzer sekilde SpinT spinor teorisinin kurgulanabilirligi arastırılmıstır.Öncelikle Spin^T(n) grubu tanımlanmış ve bu grubun bazı özellikleri araştırılmıştır.Düşük boyutlarda Spin^T(n) grubu incelenmiştir. Spin^c(n) grubunun temsilindenhareketle Spin^T(n) grubunun temsili verilmiştir. Yönlendirilebilir Riemann manifoldlarıüzerinde Spin^T-yapısı tanımlanmıştır. Spin^T(n) grubunun temsili kullanılarakSpin^T spinor demedi inşa edilmiştir. Daha sonra yönlendirilebilir Riemann manifolduüzerindeki Levi-Civita konneksiyonu yardımıyla Spin^T spinor demedi üzerindekovaryant türev operatörü tanımlanmıştır. Bu kovaryant türev kullanılarak Spin^TDirac operatörü tanımlanmış ve bazı özellikleri araştırılmıştır. Son olarak Spin^TDirac operatörünün Schrödinger-Lichnerowicz tipindeki formüle benzer bir formülüsağladığı gösterilmiştir. In this thesis, the constructability of Spin^T spinor theory similar to known Spin^cspinor theory is investigated on the orientable Riemannian manifolds. Firstly, thegroup Spin^T(n) is defined and some properties of this group are studied. In lowdimensions, the group Spin^T(n) is examined. With the aid of the representation ofthe group Spin^c(n) the representation of the group Spin^T(n) is given. The Spin^T-structure is defined on the orientable Riemannian manifolds. By using the representationof the group Spin^T(n), the Spin^T spinor bundle is constructed. Then,by the way of the Levi-Civita connection on the orientable Riemannian manifolds,the covariant derivative operator is defined on Spin^T spinor bundle. By using thiscovariant derivative, Spin^T Dirac operator is defined and some properties of Spin^TDirac operator is investigated. Lastly, Spin^T Dirac operator is showned to providea formula similar to the Schrödinger-Lichnerowicz type formula. 84

Göreli Duffin-Kemmer-Petiau denkleminin çözümleri spin-0 ve spin-1 parçacıklarının etkileşmelerinin hesaplanması ve modellenmesi için önemli rol oynamaktadır. Bilinen göreli yaklaşımda spin-0 ve spin-1 hadron çekirdekleri ile etkileşimi, spin-0 parçacıkları için ikinci mertebeden Klein-Gordon denklemi ve spin-1 parçacıkları için ikinci mertebeden Proca denklem ile tanımlanmıştır. Duffin-Kemmer-Petiau denkleminin tıpkı göreli Dirac denklemi gibi birinci mertebeden ve Lorentz değişmezliğine sahip bir denklemdir.Kuantum mekaniğinde yapılan çalışmalar konum ve momentum operatörü ile Hilbert uzayında standart Heisenberg cebri ile yapılmaktadır. Kuantum mekaniğinde minimum uzunluk gibi sonlu bir mesafe göz önüne alınmamıştır. Literatürde çok araştırılan sistemlerden biri de Lineer potansiyel problemidir.Bu çalışmada, göreli Duffin-Kemmer-Petiau denklemi kullanılarak lineer potansiyel sisteminde çözümler elde edilmiştir. Çözümler spin-0 ve spin-1 durumlarında, minimum uzunluk altında, momentum uzayında ve vektör küresel harmonikler kullanılarak yapılmıştır. Spin-0 ve spin-1 durumları için enerji özdeğerleri ve özfonksiyonları elde edilmiştir.Anahtar Kelimeler: Minimum Uzunluk , Duffin-Kemmer-Petiau Denklemi , Belirsizlik İlkesi , Planck Ölçeği Solution of the relativistic Duffin-Kemmer-Petiau equation for interaction of spin-0 and spin-1 calculation and modeling plays an important role. In the conventional relativistic approach, the interaction of spin-0 and spin-1 hadrons with different nuclei has been described by the second-order Klein-Gordon equation for spin-0 and Proca equation for spin-1 particles. Duffin-Kemmer-Petiau equation is first order and Lorentz invariance just relativistic Dirac equation.Quantum mechanics where position and momentum operators acting on the Hilbert space of states verify the standard Heisenberg algebra. They do not take into account like the existence of a minimal observable length.In this study, the linear and Coulomb potential systems solutions obtaine by using the relativistic Duffin-Kemmer-Petiau equation. Under the minimum length, solutions of spin-0 and spin-1 case investigate at the momentum space by using the vector spherical harmonics. The energy eigenvalues and eigenfunctions obtaine for spin-0 and spin-1 cases.Keywords: Minimal length , Duffin-Kemmer-Petiau Equation , Uncertainty Principle , Planck-Scale 48

In this research, we have investigated the magnetic properties of the spin-1 Ising model on the Shastry Sutherland lattice with the crystal field interaction by using the effective-field theory with correlations. The effects of the applied field on the magnetization are examined in detail in order to obtain the magnetization plateaus, thus different types of magnetization plateaus, such as 1/4, 1/3, 1/2, 3/5, 2/3 and 7/9 of the saturation, are obtained for strong enough magnetic fields (h). Magnetization plateaus exhibit single, triple, quintuplet and sextuple forms according to the interaction parameters, hence the magnetization plateaus originate from the competition between the crystal field (D) and exchange interaction parameters (J, J′). The ground-state phase diagrams of the system are presented in three varied planes, namely (h/J, J′/J), (h/J, D/J) and (D/J, J′/J) planes. These phase diagrams display the Neel (N), collinear (C) and ferromagnetic (F) phases for certain values of the model parameters. The obtained results are in good agreement with some theoretical and experimental studies.

The stabilities, structural, electronic and elastic properties of hypothetical TiXB4 (X=Li, Na, Mg and Ca) crystalline structures obtained by replacing titanium atoms, which are located 4j Wyckoff positions in Ti3B4 with Ta3B4-type structure, with Li, Na, Mg and Ca. have been investigated by performing first-principles density functional theory calculations. It is shown that calculated formation enthalpy values of all compounds are negative, and thus designed compounds are energetically stable. However, single crystal elastic constants are calculated, and except for X=Na including compound, these constants supply required criteria, therefore it is determined that TiX2B4 (X=Li, Mg and Ca) compounds are mechanically stable. On the other hand, electronic band structures of stable compounds are calculated, and it is observed that all of the compounds have metallic character. Finally, atomic charge and bond overlap population information obtained from Mulliken analysis by combining 3-dimensional electron density characteristics, bonding nature of the compounds are studied, Ta3B4-tipi kristal yapıya sahip Ti3B4 kristalinde 4j Wyckoff konumlarına yerleşen Ti atomlarının Li, Na, Mg ve Ca ile yerdeğiştirmesi sonucu elde edilen varsayımsal TiX2B4 (X=Li, Na, Mg ve Ca) katı-yapıların kararlılıkları, yapısal, elektronik ve elastik özellikleri ilk-prensipler yoğunluk fonksiyonel teorisi (DFT) hesaplamaları yapılarak incelendi. Hesaplanan oluşum entalpilerinin bütün yapılar için negatif olduğu, böylece tasarlanan bileşiklerin enerjitik kararlı oldukları görüldü. Bununla birlikte, yapıların elastik sabitleri (cij) hesaplandı ve X=Na’lu yapı hariç bu sabitlerin gerekli şartları sağladıkları, böylece tasarlanan TiX2B4 (X=Li, Mg ve Ca) bileşiklerinin mekanik kararlı oldukları tespit edildi. Diğer taraftan, kararlı yapıların elektronik bant yapıları çizildi ve hepsinin metalik karakterde oldukları belirlendi. Mulliken analizinden elde edilen atomik yük ve bağ overlap popülasyon bilgileri 3-boyutlu elektron yoğunlukları ile birlikte değerlendirilerek yapıların bağlanma doğası araştırıldı. Mevcut bağlanma doğasından elde edilen bilgiler hesaplamalardan elde edilen diğer parametrelerle birlikte işlenerek, bileşiklerin sertlikleri belirlendi.

The stabilities, structural, electronic and elastic properties of hypothetical TiX2B4 (X=Li, Na, Mg and Ca) crystalline structures obtained by replacing titanium atoms, which are located 4j Wyckoff positions in Ti3B4 with Ta3B4-type structure, with Li, Na, Mg and Ca. have been investigated by performing first-principles density functional theory calculations. It is shown that calculated formation enthalpy values of all compounds are negative, and thus designed compounds are energetically stable. However, single crystal elastic constants are calculated, and except for X=Na including compound, these constants supply required criteria, therefore it is determined that TiX2B4 (X=Li, Mg and Ca) compounds are mechanically stable. On the other hand, electronic band structures of stable compounds are calculated, and it is observed that all of the compounds have metallic character. Finally, atomic charge and bond overlap population information obtained from Mulliken analysis by combining 3-dimensional electron density characteristics, bonding nature of the compounds are studied.

Although the conventional ring spinning technique has a wide field of usage, the handicap of yarn production at high speeds in ring spinning system is defined as a major problem among the producers. But this situation had a positive contribution for the investigation of the new spinning systems. The Compact Spinning System, Sirospun, Duospun which are developed as the modification of the ring spinning system, open-end rotor systems, frictional spinning, air jet spinning system and vortex spinning system are the most important new yarn spinning systems which are well known and commonly being used in textile sector. In Recent Years the vortex and air-jet yarn spinning technologies where the swirling air technique for the yarn production is used, have provided important advantages of reaching the final product with minimum cost, at high speeds but with the right quality. This study aims to give some information about the short staple yarn spinning systems developed after the ring spinning and also to demonstrate the advantages of new spinning systems, Konvansiyonel Ring iplik eğirme tekniği geniş bir kullanım alanına sahip olmasına karşın yüksek hızlara çıkılamaması üreticiler açısından önemli bir sorun olarak belirlenmiştir Bu durum ise yeni iplik eğirme yöntemlerinin araştırılmasına olumlu katkılar sağlamıştır. Ring iplik eğirme sisteminin modifikasyonu ile geliştirilen; kompakt, Sirospun ve Duospun iplik eğirme sistemleri, açık uç-rotor iplik eğirme sistemi, friksiyon eğirme, hava jetli eğirme ve vorteks iplik eğirme sistemleri bilinen ve sektörde sıklıkla kullanılan önemli yeni iplik üretim sistemleridir. Son yıllarda dönen hava prensibi ile iplik üretimi sağlayan vorteks ve hava jetli sistemler minimum maliyet, yüksek hız ve kaliteye ulaşabilme konusunda önemli avantajlar sağlamıştır. Bu çalışmanın amacı ring iplik eğirme teknolojisinden sonraki kısa stapel iplik üretim sistemleri hakkında bilgi vermek ve yeni iplik eğirme teknolojilerinin avantajlarını ortaya koymaktır.

In this work we have studied the electronic mobility m within a completely disordered lattice system by using the strong interatomic hopping potential V(r) = ( - {\frac{{r}}{{ao} }}) \exp( - r / ao ) for site representation of the Hamiltonian. It is shown that a metallic system of a completely disordered lattice first goes insulating and then goes back to metallic again at higher atomic density r .

High-temperature superconducting ceramics systems YBaCuO and BiSrCaCuO, both doped by Pb, Sb, Li, K, Na and non-doped, have been produced by the method of solid phase reaction synthesis. The principle of controlled valency by Vervey has been used to characterize high-temperature superconductors. High-temperature superconducting ceramics have been obtained with properties stable in time by single-purpose doping.

By using the dielectric continuum approximation, the polar optical phonon modes of coaxial cylindrical quantum cables with arbitrary layer-number were studied. In order to describe the vibrating of the longitudinal-optical (LO) phonons, a set of legitimate eigenfunctions for LO phonon modes are constructed and adopted. In order to deal with the interface optical (IO) phonon modes, the transfer matrix method is employed. The quantized LO and IO phonons fields, as well as their corresponding Fröhlich electron-phonon interaction Hamiltonians, are also derived. Numerical calculations on a four-layer GaAs/AlxGa1-xAs QC have been performed. Results reveal that there are six branches of IO phonon modes. When the wave vector kz in the z direction and the azimuthal quantum number m are small, the dispersion frequencies of IO modes sensitively depend on kz and m, and the frequency forbidden behaviors of IO phonon modes were observed and the reason was analyzed. When kz and m are relatively large, with increasing kz and m, the frequency for each mode converges to the limit frequency value of IO mode in a single heterostructure, and the electrostatic potential distribution of each branch of IO mode tends to be more and more localized at some interface; meanwhile, the coupling between the electron-IO phonon becomes weaker and weaker. The calculation also shows that the phonon modes with higher frequencies have more significant contribution to the electron-phonon interaction. At last, it is found that kz and m have analogous influences on the frequencies and the electrostatic potentials of the IO phonons.

The three-site antiferromagnetic Ising, Q-state Potts (Q

Electrical properties of GaTe and GaTe:Cu binary compound semiconductors were investigated by Hall effect and resistivity measurements in the 77-320 K temperature range. Donor and acceptor densities, compensation ratios, acceptor ionization energies, valence band effective mass of holes and effective density of states in valence band were determined for the undoped and Cu doped samples using the single donor-single acceptor analysis of the hole concentration. Temperature coefficient of the hole mobility was determined and compared with related theories.

Product operator formalism is widely used for the analytical description of multi-dimensional and multiple-pulse NMR experiments for the weakly coupled spin systems having spin-1/2 and spin-1 nuclei. The INEPT NMR experiment is a polarization transfer experiment including J-coupling. In this study, the INEPT NMR experiment was analytically investigated by using product operator theory for weakly coupled ISn(14NDn) (I=1, S=1; n=1, 2, 3) spin systems. The obtained theoretical results represent the FID values of 14NDn groups. In order to make Fourier transform of the obtained FID values, a Maple program is used and then simulated spectra of the INEPT experiment are obtained for 14NDn groups. Then, the experimental suggestions are made for the INEPT NMR experiment of 14NDn groups. Also, it is suggested that the INEPT NMR experiment of IS (I=1, S=1) spin system can be used in NMR quantum computing.

The isotope effect in the recently disvovered class o superconductors LuNi2B2C and La3Ni2B2N3 is investigated in the context of electron-squezed phonon interaction renormalizing the Ni-d electron-electron correlations. Squeezed phonon mode originates from the anharmonic character of the tetragonal Ni-B structure and is polarized in the vortical direction to the Ni layers. The isotope effect arises as a result of the zero point motion of the Ni-Ni d-electron hopping amplitude dominantly due to this vertical phonon mode. Within this model the isotope exponent is calculated to be aB \leq 0.20 as compared to the recently found experimental value aBexp = 0.27 \mp 0.10. Finally, the phonon frequency softening predicted by our model eletron-phonon interaction is discussed within the context of recent experiments on the relevant boron A1g softening.

This paper reviews some recent experiments in which heat pulse techniques have been used to study the interaction of acoustic phonons with electrons in semiconductor quantum wells and wires. Heat pulse experiments provide temporal and spatial resolution of the phonons that are emitted or absorbed by the electrons and so give more detailed information about the electron-phonon interaction than can be obtained by other methods (e.g. transport measurements). Phonon experiments demonstrate clearly the effect of the electron confinement on the carrier-phonon interaction and the overall energy loss rate due to acoustic phonon emission. A qualitative explanation of the results is given in terms of the reduction of phase-space available for electron-phonon scattering when the electrons are confined in one and two dimensions. It is also shown how phonons can be used as spectroscopic probes of the electronic states in semiconductor nanostructures.

We review our recent work towards quantum communication in a solid-state environment with qubits carried by electron spins. We propose three schemes to produce spin-entangled electrons, where the required separation of the partner electrons is achieved via Coulomb interaction. The non-product spin-states originate either from the Cooper pairs found in a superconductor, or in the ground state of a quantum dot with an even number of electrons. In a second stage, we show how spin-entanglement carried by a singlet can be detected in a beam-splitter geometry by an increased (bunching) or decreased (antibunching) noise signal. We also discuss how a local spin-orbit interaction can be used to provide a continuous modulation of the noise as a signature of entanglement. Finally, we review how one can use a quantum dot as a spin-filter, a spin-memory read-out, a probe for single-spin decoherence and, ultimately, a single-spin measurement apparatus.

We review our recent results concerning the well-width dependence of the acoustic-phonon-assisted energy relaxation of two-dimensional (2D) warm electrons in modulation-doped GaAs/Ga1-xAlxAs multiple quantum wells. Electron energy-loss rates via the emission of acoustic phonons are determined from the amplitude of Shubnikov-de Haas (SdH) oscillations, measured as a function of lattice temperature and applied electric field. Experimental results are compared with the existing theoretical models that involve deformation-potential and screened and unscreened piezoelectric scattering. Well-width dependence of the quantum and transport mobilities of 2D electrons in the same samples have also been determined by measuring the quantum oscillations in both the magnetoresistance and Hall resistance. Our results confirm earlier independent conclusions that the momentum relaxation in GaAs/Ga1-xAlxAs multiple quantum wells is limited mainly by interface roughness scattering. A new theoretical modelling has been proposed and used to estimate the interface roughness parameters from the measured quantum and transport mobilities of 2D electrons.

A study is made for the magnetic excitations and their Anderson localization properties for a Heisenberg ferromagnet with random anisotropic fields. The system is assumed to be in a strong applied field so that complete spin alignment is established. The magnetic excitations, i.e., the harmonic spin waves, are computed using coherent-field-anisotropy approximation (a version of coherent potential approximation of the electronic problem). The spin wave shift and damping are calculated using the computed coherent field which is a complex function of energy approximating the random medium as a mean field level. The localizaton of the excitations are calculated by adopting the analogous results of the electronic problem. The model investigated here can be applicable to amorphous magnets in the low energy limit.

Low-magnetic field microwave absorption (MA) in superconductors and conducting polymers is analysed in a low-field signal (LFS) version of the MA detecting method. The temperature dependences, hysteretic benavior and other properties of a LFS are compared in superconducting versus non-superonducting systems. Spin selective hopping processes between polarons and bipolarons is proposed to be one of the possible mechanisms of a LFS in non-degenarate conducting polymers.

In this paper a variational study of a tunnelling exciton (Frenkel exciton) coupled to an arbitrary number of phonon modes is presented. The results of our model are presented both for weak non-adiabatic cases and for strong cases; and we come to the conclusion that the tunnelling reduction factor, the ground state energy of the tunnelling exciton-phonons system, and the mean number of ground state phonons, as the functions of the exciton-phonons coupling strength, are continuous, a condition that does not apply in cases of the tunnelling exciton-phonons models presented in the previous studies. In comparison with the previous studies, the presented model leads to a significant decrease of the ground state energy both of the small polaron and of the tunnelling exciton-phonons system, mainly for weak non-adiabatic cases.

We present the first study of the effect of ballistic acoustic phonons generated by a heated metal film on the tunnel current in GaAs/AlAs superlattices. The phonon-induced increase of the tunnel current as a function of applied voltage has a maximum at a voltage that varies linearly with heater temperature both in zero and applied magnetic field. The behaviour is consistent with phonon-assisted tunnelling by stimulated phonon emission. The system acts as a phonon spectrometer in the < 1THz frequency region with a resolution of approximately 200 GHz.

The partial occupation numbers and density of states (DOS), and the total DOS at the Fermi level are calculated as a function of reduced atomic volume for bcc and fcc alkali metals employing the linear-muffin-tin-orbital (LMTO) method. By means of the abrupt changes obtained in the partial and total DOS values at the Fermi level, good agreement with regard to experiment were found in predicting the bcc-fcc transition volumes of the alkali metals.

In this paper, some theorems involving inequalities on p-valent functions (that is p-valenty close-to-convex functions, p-valently starlike functions, and p-valently convex functions) are given. Moreover, some applications in the theorems which are important for geometric function theory are also included. Keywords: Analytic, p-valent, p-valently colse-to-convex functions, p-valently starlike functions, p-valently convex functions, open unit disk, and Jack's Lemma.

Making use of fractional derivative operator, we introduce a general class of functions which are analytic and p-valent in the open unit disk U, and obtain a necessary and sufficient condition for a function to be in the class , distortion bounds, inclusion property and the radii of p-valently close-to-convexity, p-valently starlikeness, p-valently convexity for this generalized class of p-valent function.2000 Mathematics Subject Classification. Primary 30C45, 26A33, Secondary 33C05