 Article
Authors: Nguyen, Quang Bau; Nguyen, Van Hieu; Nguyen, Thi Thanh Huyen; Nguyen, Dinh Nam; Tran, Cong Phong (2009)  The acoustomagnetoelectric effect in a superlattice is investigated for an acoustic wave whose wavelength is smaller than the mean free path l of the electrons and hypersound in the ragion (where q is the acoustic wave number). All the results are compared with the normal bulk semiconductors (both theory and experiment) in the weak magnetic field region to show the difference.

 Article
Authors: Nguyen, Quang Bau; Dinh, Quoc Vuong; Nguyen, Ba Lam; Luu, Bich Linh (2004)  Analytic expressions for the highfrequency conductivity tensor and the absortion coefficient of a weak electromagnetic wave (EMW) due to free carriers for the case of electronacoustic phonon scattering in Quantum Wires are calculated by using the KuboMori Method in two cases: the absence of a magnetic field and the presence of a magnetic field.

 Article
Authors: Cao, Thi Vi Ba; Tran, Hai Hung; Doan, Minh Quang; Nguyen, Quang Bau (2017)  The Ettingshausen coefficient (EC) in a Rectangular quantum wire with an infinite potential (RQWIP)in the presence of an Electromagnetic wave (EMW) is calculated by using a quantum kinetic equation for electrons. Considering the case of the electron  optical phonon interaction, we have found the expressions of the kinetic tensors . From the kinetic tensors, we have also obtained the analytical expression of the EC in the RQWIP in the presence of EMW as function of the frequency and the intensity of the EMW, of the temperature of system, of the magnetic field and of the characteristic parameters of RQWIP. The theoretical results for the EC are numerically evaluated, plotted and disc...

 Article
Authors: Bui, Dinh Hoi; Pham, Thi Trang; Nguyen, Quang Bau (2013)  We consider a model of the Hall effect when a doped semiconductor superlattice (DSSL) with a periodical superlattice potential in the zdirection is subjected to a crossed dc electric field (EF) and magnetic field , in the presence of a laser radiation characterized by electric field (where and are the amplitude and the frequency of the laser radiation, respectively). By using the quantum kinetic equation for electrons and considering the electron  optical phonon interaction, we obtain analytical expressions for the Hall conductivity as well as the Hall coefficient (HC) with a dependence on B, , , , the temperature T of the system and the characteristic parameters of DSSL. The an...

 Article
Authors: Hoang, Dinh Trien; Bui, Thi Thu Giang; Nguyen, Quang Bau (2010)  The nonlinear absorption of a strong electromagnetic wave caused by confined electrons
in cylindrical quantum wires is theoretically studied by using the quantum kinetic equation for
electrons. The problem is considered in the case electronacoustic phonon scattering. Analytic
expressions for the dependence ofthe nonlinear absorption coeflicient ofa strong electromagnetic
wave by confined electrons in rectangular quantum wires on the terrperature T are obtained. The
analytic expressions are numerically calculated and discussed for GaAs/GaAsAl rectangular
quantum wires.

 Article
Authors: Hoang, Dinh Trien; Nguyen, Vu Nhan; Do, Manh Hung; Nguyen, Quang Bau (2009)  The parametric transformation of acoustic and optical phonons in doped superlattices is theoretically studied by using a set of quantum kinetic equations for the phonons. The analytic expression of parametric transformation coefficient of acoustic and optical phonons in doped superlattices is obtained, that depends nonlinear on the concentration of impurities. Numerical computations of theoretical results and graph are performed for GaAs:Si/GaAs:Be doped superlattices.

 Article
Authors: Nguyen, Thi Thanh Ha; Nguyen, Quang Bau; Pham, Khac Hung (2012)  In this paper, we numerically study the diffusion mechanism at atomic level in silica liquid via molecular dynamics simulation. The model consisting of 1998 particles and using the BKS potential has been constructed at the temperature from 2600 to 4500 K. Furthermore, we track the evolution of network units with x=4, 5 and 6 over different time. The simulation shows that the diffusivity depends strongly not only on the rate of the exchanging the coordinated oxygens, but also on the correlation effect. This effect is caused by the specific distribution of the exchanging coordinated oxygens (ECO) through the space which leads to spatially heterogeneous dynamics in the liquid. Analyzing ...

 Article
Authors: Nguyen, Quang Bau; Do, Tuan Long (2016)  Based on the quantum kinetic equation method, the Hall effect in doped semiconductor superlattices
(DSSL) has been theoretically studied under the influence of confined LOphonons and the laser radiation. The analytical expression of the Hall conductivity tensor, the magnetoresistance and the Hall coefficient of aGaAs:Si/GaAs:BeDSSL is obtained in terms of the external fields, lattice period and doping concentration. The quantum numbers N, n, m were varied in order to characterize the effect of electron and LOphonon confinement. Numerical evaluations showed that LOphonon confinement enhanced the probability of electron scattering, thus increasing the number of resonance peaks in ...

 Article
Authors: Le, Thai Hung; Nguyen, Vu Nhan; Nguyen, Quang Bau (2012)  The impact of confined phonons on the nonlinear absorption coefficient (NAC) of a strong electromagnetic wave (EMW) by confined electrons in compositional superlattices is theoretically studied by using the quantum transport equation for electrons. The dependence of the NAC on the energy (), the amplitude (Eo) of external strong EMW, the temperature (T) of the system and the period (dA) of compositional superlattices is obtained in both case of confined and unconfined phonons. Two cases for the absorption: Close to the absorption threshold and far away from the absorption threshold (; and are the energy of optical phonon and the average energy of electrons, respectively) are consi...

 Article
Authors: Nguyen, Quang Bau; Cao, Thi Vi Ba; Do, Tuan Long (2017)  Based on the quantum kinetic equation method, the influence of confined optical phonons and laser radiation on the Radioelectric effect in a cylindrical semiconductor quantum wire with parabolic potential subjected to a dc electric field and a linearly polarized electromagnetic wave has been theoretically studied. The obtained analytical expression of the Radioelectric field (REF) depends on frequencies and amplitudes of the external electromagnetic waves, the quantum wire parameters, the temperature of the system, and especially the quantum numbers (n and m) which characterize the phonon confinement. Numerical calculations for the GaAs/GaAsAl quantum wire show the strongly impact of ...

 Thesis
Authors: Bui, Hong Phuong; Advisor: Nguyen, Quang Bau (2011)  Nghiên cứu siêu mạng pha tạp và bài toán ảnh hưởng của trường bức xạ laser lên hấp thụ sóng điện từ yếu bởi điện tử trong bán dẫn khối. Giới thiệu phương trình động lượng tử và hệ số hấp thụ sóng điện yếu từ bởi điện tử giam cầm trong siêu mạng pha tạp khi có mặt trường bức xạ Laser (trường hợp tán xạ điện tử  phonon âm). Trình bày về Tính toán số và đưa ra một số kết luận nghiên cứu

 Article
Authors: Nguyen, Quang Bau; Dao, Thu Hang; Doan, Minh Quang; Nguyen, Thi Thanh Nhan (2017)  We have studied magnetothermoelectric effects in quantum well in the presence of electromagnetic wave. The analytic expression for Ettingshausen coefficient (EC) in the Quantum Well with parabolic potential (QWPP) in the presence of Electromagnetic wave (EMW) is calculated by using the quantum kinetic equation for electrons. The dependence of EC on the frequency, the amplitude of EMW, the Quantum Well parameters and the temperature are obtained. The results are numerically calculated, plotted, and discussed for GaAs/GaAsAl Quantum Well to clearly show the dependence of EC on above parameters and the results in this case are compared with the case in the bulk semiconductors. We realiz...

 Article
Authors: Nguyen, Quoc Hung; Nguyen, Quang Bau (2002)  Based on the quantum kinetic equation for phonon, the amplification of sound (acoustic phonons) due to the absorption of laser radiation in cylindrical
quantum wires with parabolic potential in the presence of m agnetic field is studied.
Analytical expressions for the rate of acoustic phonons excitations, the conditions for the amplification of sound and the momentum conditions for electron to participate in the amplification of sound are obtained for the two cases: singlephoton absorption process and multiphoton absorption process. The differences between the two cases of singlephoton absorption and m ultiphoton absorption are discussed; the numerical computations and plots are car...

 Article
Authors: Dang, Dinh Toi; Nguyen, Quang Bau (2002)  By suggesting a simple density of localized states for amorphous materials and using the percolation method the analytical expression is obtained for
describing qualitatively the observed variablerange hopping thermopower crossover from the Mott T l/2 behaviour to the temperatureindependent behaviour as the temperature increases. The crossover shows a profound manifestation of the Coulomb correlation along that observed in VRH conductivity crossover.

 Article
Authors: Nguyen, Quang Bau (2006)  Analytic expressions for the obsorption coefficient of a weak Electromagnetic Wave (EMW) by free carriers for the case electronoptical phonon scattering in 2 dimensional system (quantum wells and doped superlattices) are calculated by the KuboMori method in two cases: the absence of a magnetic field and the presence of a magnetic field applied perpendicular to its barriers, A different dependence of the absorption coefficient on the temperature T of system, the electromagnetic wave frequency , the cyclotron frequency n (when a magnetic field is present) and characteristic parameters of a 2 dimensional system in comparision with normal semiconductors are obtained. The analytic ex...

 Article
Authors: Nguyen, Thi Thanh Ha; Nguyen, Anh Dung; Nguyen, Quang Bau; Pham, Khac Hung (2016)  We have studied the diffusion mechanism in networkforming liquids via molecular dynamics simulation. Two models of silica liquid at temperatures of 2600 and 3500 K have been constructed. The motion of atoms is analyzed through reactions SiOx®SiOx±1, OSiy®OSiy±1 and coordination cells. It was shown that the reactions happen not randomly in the space, but they occur more frequently with some coordination cells and bonds SiO. This effect enhances upon lowering the temperature. The number of reactions happening in the coordination cells is strongly correlated with the mobility of CC atom. We found that there are large rigid clusters which compose of immobile atoms and exist for long tim...

 Article
Authors: Nguyen, Quoc Hung; Nguyen, Quang Bau (2003)  Based on the quantum kinetic equation for the electronphonon system, the amplification of sound (acoustic phonons) by absorption of a laser radiation in quantum wires with parabolical potential is studied for the case of monophoton absorption process and the case of multiphoton absorption process. Analytical expressions and conditions for the rate of acoustic phonons exciation are obtained.

 Article
Authors: Le, Thai Hung; Nguyen, Quang Bau; Pham, Ngoc Thang (2017)  The Transverse Hall effect (THE) has been theoretical studied in a quantum well (QW) with high infinite potential subjected to a crossed dc electric field and a magnetic field (MF) which is oriented perpendicularly to the confinement direction in the present of an intense electromagnetic wave (EMW). The analytical expression of the transverse hall coefficient (THC) which depends not only on the parameters of the system but especially on the quantum number m characterizing confined phonons, is obtained by using the quantum kinetic equation method for confined electrons  confined optical phonons interaction. The analytic expression of THC is numerically evaluated, plotted and discussed...
