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Special CAMP: Majorana modes, transport across superconductor - normal metal junctions, and parity blocking in quench dynamics

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Diptiman Sen, India Institute of Science, Bangalor
When
27 February 2015 from 10:00 AM to 11:00 AM
Where
339 Davey Laboratory
Contact Name
Jainendra Jain
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We discuss our work on a p-wave superconducting wire, in particular,

the Majorana modes which appear at the ends or inside the wire in various

situations, and the effects of these modes on the conductance across the

system and its quench dynamics.

 

For a finite length wire, the two Majorana end modes hybridize; this shifts

their energies and hence the peaks in the differential conductance away

from zero. The energy shifts oscillate and decrease as the wire length

is increased. If the p-wave pairing amplitude changes sign at some point

inside the wire, two more Majorana modes appear there; we discuss the

effect of these modes on the conductance. We use a renormalization group

approach to study the effect of electron-electron interactions on the

Majorana modes. Finally, we propose experimental realizations of our model.

 

When one of the parameters of a p-wave superconducting wire with open

boundary conditions is changed in time (called a quench), we find that

the overlap between the time-evolved state and the instantaneous ground

state repeatedly becomes zero. This occurs because the fermion number

parity of the instantaneous ground state repeatedly flips between +1

and -1; this is due to the energy of the Majorana end modes oscillating

through zero. We call the phenomenon of the overlap being zero at certain

times as parity blocking. We study this both analytically and numerically

and show that the fermion parity gives rise to a rich texture within the

topological phase diagram of the system.

 

 

References:

 

1. M. Thakurathi, O. Deb and D. Sen, arXiv:1412.0072

 

2. S. Hegde, V. Shivamoggi, S. Vishveshwara and D. Sen, arXiv:1412.5255

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