Atomistic Modeling of Nano Devices: From Qubits to Transistors

By Rajib Rahman

Purdue University, West Laffayette, IN

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While  the  end  of  Moore’s  Law  marks  the  end  of  the  glory  days  of  electronic  devices,  it  also  opens  up   opportunities   to  explore   novel  concepts   in  computation   and   device   design.   Use  of  the  spin   degrees   of  freedom   has   attracted   much  attention   in  both   classical  computing   and   in  the  emerging   field  of  quantum   computing.   However,   spins  at   the  nanoscale  are  susceptible  to  the  inhomogeneous   local  environment  of  the  devices  through  their  coupling  to  charge   and   valley  degrees   of  freedom,   and   to  other   atoms  of  magnetic   nature.   To  understand   how   these  atomic  scale  magnetic   interactions   manifest  in   the  behavior   of  devices,  atomistic  modeling   techniques   are   needed   that  unify  the  treatment   of   spin  and   charge   and   provide   a   description   of  electronic   structure  and   carrier   transport   from   a  fully  quantum   mechanical   standpoint.   In  this  talk,  I  will   describe   such  a  framework   that  can  capture   complex  interactions   ranging   from  exchange   and  spin-orbit-valley  coupling  in  spin  qubits to  non-equilibrium   charge  transport  in  tunneling  transistors.  I  will  show  how   atomistic  full  configuration  interaction  calculations  of  exchange  in  donor  qubits help  to  propose  an  improved  two-qubit gate   in  silicon.  I  will  also   show   how   spin-orbit-valley   coupling   due   to  interface   roughness   affects  the  spin  resonance   frequencies   and   spin  lifetimes  in  silicon  quantum   dots.  Finally,   I  will  show   how   atomistic  transport   simulations  help   to   identify  the  best  2D   materials   and   designs   for  tunnel   transistors.


Rajib Rahman Rajib Rahman  obtained  his  PhD  degree  in  Electrical  and  Computer  Engineering   from  Purdue  University  in  2009  in  the  area  of   computational   nanoelectronics.   Subsequently,   he  was  a  postdoctoral   fellow   in  Sandia   National   Laboratories   in  the   Silicon   Quantum   Information   Science   and  Technology   group.   Since  2012,   he  has  been  employed   as  a  Research  Assistant   Professor  in  the  Network   for   Computational   Nanotechnology   (NCN)  at  Purdue.   Rajib develops   and  employs   atomistic   simulation   methods   to  model   spin  qubits in   semiconductors   taking   into   account  their   complex   interaction   with  the   environment   in  the  form  of  electron-­electron,   electron-­phonon,   and   magnetic   interactions.   He  collaborates   with  leading   experimental   groups  from  Australia,   Netherlands,   and  USA  in  the  field  of  silicon  quantum   computing.   At  Purdue,   Rajib also   works  on  atomistic   transport   simulations   of  energy  efficient   transistors  in  emerging   2D  materials.

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Researchers should cite this work as follows:

  • Rajib Rahman (2016), "Atomistic Modeling of Nano Devices: From Qubits to Transistors,"

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