Questions on sequential tunneling

[kaypu]

Dear QuantumWise staff:
     
      A few days ago, i was fortunate to read the paper by professor Anders and Kurt (IEEE,2011), it is very helpful. Sequential tunneling mentioned in the paper puzzle me a lot. 

i don't know what' the different between Sequential tunneling, incoherent tunneling, hopping, and Coulomb blockade regime?

in my view:
Ⅰ. ①(the length of central molecule is smaller than 2.5nm). if the molecule-electrode coupling is strong, the transport regime is coherent tunneling, the incident wave function tunnel through the electrostatic potential field  does not cause any change of the electrostatic potential field. it is to say that the incident electron need only one step from left electrode to right electrode. if the bias is low, there is no "molecule energy" in the bias window the tunneling is weak, if the bias is high, some molecule eneries in the bias window, the tunneling is orbital-mediated and it is strong. DFT-NEGF(ATK) can deal with it very powerful.
Am i right?

②(the length of central molecule is longer than 2.5nm). the incident electron will stay for a long time in a potential well of the central molecule, the phase of incident electron is changed due to the interaction. at this time, incoherent tunneling is the main transport regime, and it can be decompose into a series of coherent tunneling. is it means Sequential tunneling?  i only know hopping is temperature-dependent, tunneling is not, and hopping is over the barrier, tunneling is through the barrier.what' the different between Hopping and sequential tunneling?
 

Ⅱ. if the molecule-electrode coupling is weak, couloumb blockade effect between the molecule and electrode is established, the electron spend long enough time stay in the central region, so, electron(incident)-electron(molecule) exchange-correlation interaction and interaction between incident electron wave and molecule vibration can't be neglected. the interaction lead to Kondo effect(at Kondo temperture) and inelastic tunneling. DFT-NEGF(ATK) can not simulate.  Am i right?


Regards
kaypu





     

[kstokbro]

sequential tunneling and hopping is the same,
check also
http://www.quantumwise.com/documents/tutorials/latest/BenzeneSET/index.html/chap.background.html

[kaypu]

Thank you  professor kstokbro
another question, what's the different between incoherent tunneling and  inelastic tunneling? the same?

Regards

[Anders Blom]

Not necessarily, you can in principle have incoherent elastic tunneling. Inelastic means the electrons loses (or gains) energy through some scattering while traversing the system, typically due to electron-phonon interaction. Incoherent means the transport is diffusive, as opposed to coherent = a single wave function extending throughout the system.

[kaypu]

Thank you professor Anders and happy new year