Calculation of the Ettingshausen Coefficient in a Rectangular Quantum Wire with an Infinite Potential in the Presence of an Electromagnetic Wave

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The theoretical results for the EC are numerically evaluated, plotted and discussed for a specific RQWIP GaAs/GaAsAL. We also compared received EC with those for normal bulk semiconductors and quamtum wells to show the difference. The Ettingshausen effect in a RQWIP in the presence of an EMW is newly developed.

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Nội dung Text: Calculation of the Ettingshausen Coefficient in a Rectangular Quantum Wire with an Infinite Potential in the Presence of an Electromagnetic Wave

VNU Journal of Science: Mathematics – Physics, Vol. 33, No. 4 (2017) 17-23 Calculation of the Ettingshausen Coefficient in a Rectangular Quantum Wire with an Infinite Potential in the Presence of an Electromagnetic Wave (the Electron - Optical Phonon Interaction ) Cao Thi Vi Ba, Tran Hai Hung*, Doan Minh Quang, Nguyen Quang Bau Faculty of Physics, VNU University of Science, 334 Nguyen Trai, Hanoi, Vietnam Received 11 October 2017 Revised 24 October 2017; Accepted 25 October 2017 Abstract: 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  ik , ik , ik , ik . 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 discussed for a specific RQWIP GaAs/GaAsAL. We also compared received EC with those for normal bulk semiconductors and quamtum wells to show the difference. The Ettingshausen effect in a RQWIP in the presence of an EMW is newly developed. Keywords: Ettingshausen effect, Quantum kinetic equation, RQWIP, Electron - phonon interaction, kinetic tensor. 1. Introduction Nowadays, the theoretical study of kinetic effects in low-dimensional systems is increasingly interested, especially on the electrical, magnetic and optical properties of the low-dimensional systems such as: the absorption of electromagnetic waves, the acoustomagnetoelectric effect, the Hall effect, ... These results show us that there are some significant differences from the bulk semiconductor that the previous researches studied [1-12]. Among those, the Ettingshausen effect has just been researched in bulk semiconductors [13] and only been studied on the theoretical basis in 2-D systems [14]. Furthermore, no research has been done on the Ettinghausen effect in 1-D systems such as quantum wires so far. In this paper, the calculation of Ettingshausen coefficient in the Rectangular quantum wire with an infinite _______  Corresponding author. Tel.: 84-903293995. Email: haihung307@gmail.com https//doi.org/ 10.25073/2588-1124/vnumap.4236 17 C.T.V. Ba et al. / VNU Journal of Science: Mathematics – Physics, Vol. 33, No. 4 (2017) 17-23 18 potential in the presence of magnetic field, electric field under the influence of electromagnetic wave is done by using the quantum kinetic equation method that brings the high accuracy and the high efficiency. Comparing the results obtained in this case with in the case of the bulk semiconductors and quantum wires, we see some differences. To demonstrate this, we estimate numerical values for a GaAs/GaAsAl quantum wire. 2. Calculation of the Ettingshausen coefficient in a Rectangular quantum wire with an infinite potential in the presence of an electromagnetic wave In a model, we consider a wire with rectangular cross section (Lx  Ly) and the length Lz. The effective mass of electron is denoted as m. The RQWIP is subjected to a crossed dc electric field E1  ( 0,0,E1 ) and magnetic field B  ( B,0,0 ) in the presence of a strong EMW characterized by electric field E( t )  E0 sin(  t ) (with E0 and  are the amplitude and the frequency of LR, respectively). Under these condition, the wave function and energy spectrum of confined electron can be written as:   ,k ( x, y,z)  1 i kz e Lz 0  x  Lx 2 n x 2 l y  sin( ) sin( ) when  Lx Lx Ly Ly  0  y  Ly (1) and   ,k ( x, y,z)  0 if else. k z2  2 2  n2 l 2  1 1  eE1   ( k )    2  2   c ( N  )    2m 2m  Lx Ly  2 2m  c  2 2 (2) eB is the cyclotron frequenciesn;  and ‟ are the m quantum numbers (n,l) and (n,l‟) of electron; N, N‟ are the Landau level (N=0,1,2,…). These expressions differ from the equivalent expressions in bulk semiconductors [14] and quantum wells [13]. The Hamiltonnian of the electron - optical phonon interaction system in the above RQWIP can be written as: e H     ( k  A( t ) )a,k a ,k   q bq bq  c q  ,k (3) 2 2    Cq I  , ' ( q ) a ,k  q a ',k ( bq  bq )  ( q )a,k  q a ',k where kz is the electron wave momentum; c   , ',k ,q q   ,k Where a  q and a ,k ( b and bq ) are the creation and the annihilation operators of electron (optical phonon); k is the electron wave momentum; q is the phonon wave vector; q are optical phonon  1 1    (here V is     0  is magnetic permeability of high frequency dielectric,  0 is magnetic frequency; Cq the electron – optical phonon interaction constant: | Cq |2 = the unit normalization volume,   e2o 2 0 q 2V permeability of static dielectric; I , ' ( q ) is the electron form factor, which is determinned by [8], different from that in cylindrical quantum wire;   q  is the potential undirected: C.T.V. Ba et al. / VNU Journal of Science: Mathematics – Physics, Vol. 33, No. 4 (2017) 17-23   q    2 i  ( eE  c [ q,h ]) 3   q  q 19 (4) ( h is unit vector in the direction of magnetic field). Through some computation steps, the quantum kinetic equation takes the form: e  m kn  ,k ,k δ(ε  ε ,k ) τ   n ,k e kF  m  ,k  k  e  c  h , kn ,k δ(ε  ε ,k m   ,k  2 e  δ(ε  ε ,k )   Cq m  , ' ,q ,k   2   n ',q  k  n ,k   1  2 2   2  )   2 I  , ' ( q ) N q k   2           ',k  q    ,k  o     o  ',k  q  ,k 4 2         2 2             n  n 1      ',k  q    ,k  o  o    ',k  q  ',k  q  ,k  ,k   4 2 2 2     2 2             ',k  q    ,k  o   o  ',k  q  .k 4 2 4 2       (5)     ( ε  ε  ,k  ) Equation (5) we put: R(  )    ,k Q(  )   S(  )  e kn δ(ε  ε ,k ) m  ,k  n ,k e kF  m  ,k  k (6)    F  T;  δ(ε  ε ,k ) ; F  e.E1  T  (7) 2 2 e 2 C(q) I  , ' ( q ) N q k   m  , ' ,q ,k  2  2   n ',q  k  n ,k   1            ',k  q    ,k  o     o  ',k  q  ,k 2 2  4 2          2 2             n  n 1      ',k  q    ,k  o  o    ',k  q  ',k  q  ,k  ,k   4 2 2 2     2 2             ',k  q    ,k  o   o  ',k  q  .k 4 2 4 2       (8)     ( ε  ε  ,k  ). We obtain the following equations: R(  )        (  ) Q(  )  S(  ),h h . 2 2 c   ( ) Q(  )  S(  )  c  (  ) h ,Q(  )  h ,S(  )  1  c2 2 (  ) (9) C.T.V. Ba et al. / VNU Journal of Science: Mathematics – Physics, Vol. 33, No. 4 (2017) 17-23 20 After some approximate developing and computation steps, we obtain the expression of Ettinghausen coefficient as follows:  xx xy   xy xx 1 (10) P H  xx   T  xx   xx  T  K L  xx  xx    Here: ea eb 2 ea eb 2  ( 1  c2 2 ) ;  xy  .c  .c . 2 2 2 2 2 2 1  c  m 1  c  m 1   2 2  1   2 2  (11) eb 2 .( 1  c2 2 ). 2 mT 1   2 2  (12)  xx  b 2 b 2 .( 1  c2 2 ). ;   .   . xy c 2 2 m m 1   2 2  1   2 2  (13) T  b  .( 1  c2 2 ). 2 mT 1   2 2  (14)  xx  c  xx  c c c xx 2 c 2 c 1/ 2 e Lx  2m  a  2  4m     b 2 eNo m 2  1  eE1   2 2  n2 l 2  1       exp  β  ε F   2  2   c  N        2m  c  2m  Lx Ly  2        (A A    1 2 , '  1 1   A3  A4  A5  A6  A7  A8 )    I .I  , ' e B   o  (16) 2    2  2 2  n2 l 2  1  1  eE      I  exp   F   2  2   c  N       , I , '   I , ' ( q ) dq   2m  Lx Ly  2  2m  c          Lx kBTe2   B2 A1  e 8 2 3 11 A2   A3      B211  B e  ( 2B11m )1/ 2 K 1 (  11 )2   2  2  2 m  Lx kBTe4 Eo2 B11    B2 e 16m2 (  / 8m )3/ 2  4 11  1     B11    Lx kBTe4 Eo2 B13    B2   Lx kBTe4 Eo2 B14    B2  1  1  e   , A  e      4 2 3/ 2 4 2 3/ 2 4 16m (  / 8m )  B13  16m (  / 8m )  B14    13  Lx kBTe2   B4 A5  e 8 2 3 15 A6   14     B215  B e  ( 2B15 m )1/ 2 K 1 (  15 )2   2  2  2 m  Lx kBTe4 Eo2 B15    B2 e 16m2 (  / 8m )3 / 2  4 15  1     B15   (15) (17) C.T.V. Ba et al. / VNU Journal of Science: Mathematics – Physics, Vol. 33, No. 4 (2017) 17-23 A7   Lx kBTe4 Eo2 B17    B2  1 e   16m2 (  / 8m )3 / 2  4 B 17  B11  17  n' 2  n2 l' 2  l 2   2m  L2x L2y 2 2   Lx kBTe4 Eo2 B18    B218 , A  e  8 2m2 (  / 8m )3 / 2  4  21  1     B18      c  N'  N   o ,  B13  B11   , B14  B11   , B15  B11  2o , B17  B15   , B18  B15   Here   1 / ( kBT ) ; hx  0,hy  0,hz  1; K L ,  ,T ,k B , 0 ,  ,  F :is the lattice heat conductivity, the momentum laxation time, the temperature, the Boltzmann constant, the static dielecttric constant, the high frequency dielectric constant, and the Fermi level, respectively. The expressions of the kinetic tensors  ik , ik , ik , ik (11-14) and of the EC (10) as well as functions 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 are different from those in bulk semiconductors and quamtum wells. It is newly developed in the quantum theory of Ettinghausen effect. 3. Numerical results We will survey, plot and discuss the expressions for the case of a specific GaAs/GaAsAl quantum well. The parameters used in the calculations are as follows:   10.9,   12.9, 0  36.25meV ,   5320 kg.m 3 ,  3.10 13 s 1 ,  F  50meV ,  10 12 s,Lx  8.10 9 m,Ly  7.10 9 m,m  0,067.m0 ( m 0 is the mass of a free electron ) In Fig. 1, we show the dependence of the EC on the laser frequency. From the figure, we see that the EC in RQWIP decreased is nonliner with the frequency, however, the EC in the quantum wells increased with the frequency [14]. This also demonstrates its difference in bulk semiconductors [13]. In Fig. 2, we show the dependence of the EC on laser amplitute. We found that the EC in RQWIP decreased is nonliner with laser amplitude. This is similar in the case of quantum wells, however, the EC in the quantum wire has decreased much faster than in quantum wells and in bulk semiconductors [13,14]. Fig 1. The dependence of EC on laser frequency. Fig 2. The dependence of EC on laser amplitute.