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ديناميكية الالكترون في كيوبت مقترن بنقطة اتصال كمية == The Electron Dynamics in Qubit Coupled to Quantum Point Contact

Author name: ايات طاهر ابراهيم

Supervisor name: جنان نجيد المخ

General topic: Physics

Specific topic: Electronics Physics

Degree: Doctorate

University: University Of Basrah - College Of Education For Pure Sciences

Language: English

University location: Basrah

First pages:

تعزيز الفوتون لنقل الالكترون خلال النظام النانوي QD - QW - QD == Photon – Assisted Electron Transport through QD – QW – QD Nanostructure System

Author name: هشام يوسف المهدي

Supervisor name: Shakir I . Easa | Jenan M. Al – Mukh

General topic: Physics

Specific topic: Electronics Physics

Degree: Doctorate

University: University Of Basrah - College Of Education For Pure Sciences

Language: English

University location: Basrah

First pages:

دراسة نظرية لتاثير مجال خارجي معتمد على الزمن على قناتي البرم لنظام نقطتين كميتين على هيئة T == Theoretical Treatment for the Time Dependent External Field Effect on the Spin Channels of T-shaped Double Quantum Dots System

Author name: ماجد عبد الله ناطق

Supervisor name: جنان مجيد المخ | جبار منصور خلف

General topic: Physics

Specific topic: Electronics Physics

Degree: Doctorate

University: University Of Basrah - College Of Education For Pure Sciences

Language: English

University location: Basrah

First pages:

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خصائص نقل الالكترون العابر لانظمة نقاط كمية متعددة == Transient Electron Transport Properties of Multiple Quantum Dots Systems

Author name: حسه ابراهيم عسكر

Supervisor name: شاكر ابراهيم عيسى

General topic: Physics

Specific topic: Electronics Physics

Degree: Master

University: University Of Basrah - College Of Education For Pure Sciences - Department Of Laser Physics

Language: Arabic

University location: Basrah

First pages:

Abstract: We presented a theoretical study for the electron transportcharacteristic, within a system of multi - quantum dots coupled tothe three metallic leads (right lead as an electron reservoir andtwo left leads as an electron source). We take into account twoarrangements for the scattering regions, one composed of twoquantum dots and the other is composed of four quantum dots.The study concentrated on the system parameters that has itseffect on the characteristic of the electron transfer process andhow these characteristic are affect by the number of the quantumdots in the scattering region in the both arrangements for thescattering regions.The theoretical formulism depends on the one - electron model.Where, we assigning a single effective level for each quantumdots and by taking the effects of the leads continuum levels intoaccount which are show within the wide band gap approximationto produce an imaginary quantity add to the energy levels of thequantum dots, representing the broadening in each effectivelevels.The related basic equation of motion for all the correspondinglevels eigen function probability amplitudes are solvedanalytically by using Laplace transform technique. We calculatethe occupation probability for the right lead, the instantaneouscurrent and the average instantaneous current that passes throughthe right lead.Our calculated results for the time - dependent dynamical electrontransfer offered a general features that takes into account thefollowing effects :  Energy levels position changes with respect to the leadFermi level. A suitable applied bais voltage on the right and left leads. Changes of the coupling amount among the quantum dots levels and in between them and the leads levels. Change of the leads temperatureThe characteristic of the time - dependent charge transport in the system are shown through the relation between the average instantaneous current passes the right lead and the applied baisvoltage, which we show as follow :  For the case of the scattering region arrangement that compose of two quantum dots it is an Ohmic behavior. For the case of the scattering region arrangement that compose of four quantum dots it is a non - linear (non - Ohmic) behavior.

دور تذبذب الجسر في نقل الالكترون خلال نظام مانح - جسر - قابل == THE ROLE OF BRIDGE VIBRATION ON ELECTRON TRANSFER THROUGH DONOR - BRIDGE - ACCEPTOR SYSTEMS

Author name: بهاء علي طالب

Supervisor name: شاكر ابراهيم عيسى

General topic: Physics

Specific topic: Electronics Physics

Degree: Master

University: University Of Basrah - College Of Education For Pure Sciences

Language: Arabic

University location: Basrah

First pages:

Abstract: موضوع الرسالة هو دراسة تاثير اهتزاز الجسر وتكوين البولارون الصغير على عملية انتقال الشحنة بين المانح والقابل في الانظمة الجسرية الجزيئية. ولهذا الغرض تعاملنا مع اقتران الكترون - فونون قوي. واستخدمنا لهذا الغرض معادلات الحركة لسعات الدوال الكمية للنظام الجسري مع معادلة نمط الاهتزاز الديناميكي الكلاسيكي للجسر. بخصوص التعامل مع تقريب الحالة المستقرة والتقريب الساكن تم اعطاء صيغة لحساب طاقة البولارون وتقدير تاثيرها على عملية انتقال الشحنة الديناميكية بين المانح والقابل وبارامترات النظام التي تؤثر فيها. اذ لاحظنا ان الصفة العامة في منحنيات احتماليات الملء يكون اعتمادها على طاقة الجسر المؤثرة |∆(u)| اذ بزيادتها تقل احتمالية ملء مستوى الجسر ويقل عدد التذبذبات. ان وصفنا عملية منح البولارون بواسطة نظرية البولارون الصغير طورت لوصف الترابط القوي بين الالكترون والاهتزاز ضمن مفهوم البولارون الصغير، اي ان كل جسر يمكن ان يتذبذب (شبه) غير معتمد على تذبذب جيرانه من الجسور، او كل موقع جزيئي يتذبذب غير معتمد على تذبذب موقع جزيئي اخر. فضلنا المعالجة العددية في حل المعادلات والابتعاد عن الحل المستقر وتم حل معادلة النمط الاهتزاز الكلاسيكي حلا تحليليا بحيث يكون تاثير ترابط الكترون - فونون واضحا من خلال جعل مستوى طاقة الجسر معتمد على الزمن ويكون مسيطرا على احتمالية ملء مستوى الجسر. كما ان تاثير مستويات الطاقة المستمرة للقطبين المعدنيين على كل من مستويي المانح والقابل قد اخذ بنظر الاعتبار. وكان واضحا ان احتماليات ملء المستويات تضمحل بمرور الزمن وتتضاءل سعات التذبذب في المنحنيات، وان احتمالية ملء مستوى القابل هي الاكثر تاثرا بزيادة التعريض في المستويات. وايضا لاحظنا ارتباط تصرف احتمالية ملء مستوي الجسر مع تصرف احتمالية ملء مستوى المانح وذلك لان مستوى المانح هو مصدر الالكترون لتكوين البولارون مع الجسر.V وطبقت الصيغ الرياضية على عملية انتقال الشحنة خلال جزيئة الـ DNA. اذ تعاملنا مع نظام جسري ذي جزيئة اساس واحدة ونظام جسري ذي جزيئتين من الجزيئات المتسلسلة خطيا من جزيئات الحامض النووي الـDNA. اذ لاحظنا وجود اختلاف بسيط في احتماليات ملء المستويات بوجود القاعدة G/C او القاعدة T/A، او بوجود قاعدتين جزيئيتين، اذ لاحظنا ان التصرف الهام في منحنى احتماليات الملء هو عند زيادة ترابط الكترون - فونون نلاحظ تاثير تصرف منحنى احتمالية ملء مستوى مصدر الالكترون (المانح) على تصرف منحنى احتمالية ملء مستوى الجسر الاول (القاعدة الجزيئية الاولى) التي تكون على ترابط مع المانح وذلك لحدوث تشكيل البولارون الاول. بينما يكون تصرف منحنى احتمالية ملء مستوى الجسر الثاني مع تلك للجسر الاول غير متطابق بالتصرف وذلك بسبب ضعف اصرة الترابط بينهما. ويكون تصرف احتمالية ملء القاعدة الجزيئية الثانية مترابطا مع تصرف منحنى احتمالية ملء مستوي القابل وذلك لشدة الاصرة بين مستوياتهما. | The subject of thesis is the effect of bridge vibration and small polaron formation on the electron transfer (ET) in D - B - A system. For this purpose, we dealt with strong electron - phonon coupling. And we used for this purpose the equations of motion for quantum amplitudes and the equation of classical - dynamical vibration mode of the bridge system. For the case of steady state approximation and static approximation we gave a formula to calculate the polaron energy and estimate its effect on the dynamical ET between the donor and accepter and the parameters involved. where we note that the general feature of the occupation probability curves are depend on the bridge effective energy |∆(u)|, when it increases, the occupation probability and the number of vibration decreases. The description of polaron hopping by the theory of small polaron was developed to describe the strong coupling between the electron and vibration within the concept of small polaron, i.e. every bridge vibrates (semi) independently from neighboring bridges. we preferred the numerical treatment in solving the equations and get away from the static solution, we solved the equation of classical - vibrational mode analytically such that the effect of electron - phonon coupling became obvious by putting the bridge state in a time - dependent form, and controlling the occupation probabilities of the bridge. The effects of the continuous energy levels of the metlic electrodes on the donor and acceptor states is taken into account. And it was obvious that the occupation probabilities of levels vanish in time and so as the amplitudes of vibration, and the most obvious effect of continuous levels of electrodes is on acceptor state, also we note that the behavior of the bridge state occupation probability is related with the occupation probability behavior of the donor state, since the donor state is the source of electron for polaron formation in bridge site.We applied the mathematical formulae on charge transfer through DNA molecule. Where we dealt with bridge system as a single base molecule or two liner consecutive molecules bases of DNA molecules. Where we note there is a small difference in occupation probabilities of G/C base or T/A base or between that of two bases. The important feature in occupation probabilities curves is that when electron - phonon coupling increases, we note that the effect of the occupation probability behavior curve for donor state on the occupation probability behavior curve of the first bridge which is connected with the donor because of the formation of the first polaron, while the behavior of the occupation probability of the second bridge and that of the first bridge is not coincide because of the weak interaction between them, but the occupation probability behavior of the second bridge state is related with that of the acceptor because of the strong interaction between them

خصائص نقل الالكترون لكيوبت مقترن بترانزستور الالكترون المفرد == The Electron Transport Properties of Qubit Coupled with SET

Author name: ايات طاهر ابراهيم

Supervisor name: جنان مجيد المخ

General topic: Physics

Specific topic: Electronics Physics

Degree: Master

University: University Of Basrah - College Of Education For Pure Sciences - Department Of Laser Physics

Language: Arabic

University location: Basrah

First pages:

Abstract: In this work, the dynamics of electron transport through a system consists of qubit (two coupled quantum dots) electrostatically coupled with single - electron transistor (quantum dot coupled to leads). The time - dependent Hamiltonian, that is used to describe the system energy, includes the electrostatic coupling between the qubit and the single - electron transistor. The time - dependent equations of motion for all the creation and annihilation operators are expressed in Heisenberg representation to derive the differential equations of motion for the quantum dots occupation numbers of the qubit and the single electron transistor, the related equations of motion for the correlation functions and also the formula that calculates the current which tunnels from the left lead to the single - electron transistor quantum dot. The system of equations of motion are treated by using the wide band approximation, and are solved numerically by using six order Runge - Kutta method, where the error is calculated at each step of time. By getting use of the system of differential equations solutions, the qubit and the single - electron transistor quantum dots occupation numbers are calculated as a function of time, in addition to the current that tunnels from the left lead to the single electron transistor quantum dot as a function of time.The main goal of this study in to investigate the effect of the parameters that related to the qubit and the single - electron transistor and their role in determing the electron transport process features through the whole system. These parameters, that are related to the initialization, manipulation and measurement processes, are the qubit and the single electron transistor quantum dots energy levels, the coupling strength between the qubit quantum dots, the electrostatic coupling between thequbit and the single electron transistor in addition to the coupling strength between the single - electron transistor quantum dot and the leads as well as the leads properties such as tempreture and band width. The effects of quantum dots energy levels tuning and the symmetry of the coupling with leads on the electron transport through the system are also investigated.Our study highlights four important physical features that related to the initialization, manipulation and measurement processes, these are : 1. The occupation numbers of the quantum dots of the qubit and the single electron transistor and the current of SET at the final time of measurement.2. The charge accumulation on the qubit quantum dots, at the final time of measurement, on the far - removed quantum dot and the nearest one to the single - electron transistor, that can be controlled by appling bias voltage and gate voltage.3. The determination of the time - current dependence if it follows the dependence of the far - removed or the nearest qubit quantum dot occupation number on time.4. The role of qubit energy levels tunning and the asymmetric coupling with the leads in determining the suitable initialization and manipulation processes get the quantum measurement with high quantum efficiency.

اللااستقراريات والفوضى في الدوائر الالكترونية

Author name: ابو طالب يوسف عباس عبد الكريم الشامي

Supervisor name: نوري حسين نور الهاشمي | فرات احمد مهدي السيمري

General topic: Physics

Specific topic: Electronics Physics

Degree: Master

University: University Of Basrah - College Of Education For Pure Sciences - Department Of Laser Physics

Language: Arabic

University location: Basrah

First pages:

نقل الالكترون خلال النقطة الكمية : التاثيرات الكهروحرارية وتاثيرات التبادل في نهجي كوندو ولاكوندو == Electron Transport Through A Quantum Dot: Thermoelectric Effects And Correlation Effects In Kondo And Non - Kondo Regimes

Author name: موسى كاظم شامر

Supervisor name: jenan majeed Al - mukh | shakier lbraheem easa

General topic: Physics

Specific topic: Electronics Physics

Degree: Doctorate

University: University Of Basrah - College Of Education For Pure Sciences

Language: English

University location: Basrah

First pages: