Graphene under Ultrafast LASER: An avenue for Quantum Technologies
ABSTRACT :
Analogues to spin, electrons in graphene endow an additional quantum
attribute: valley pseudospin, which is associated with the two degenerate
valleys in the energy landscape of graphene. Similar to 0 and 1, two
valleys can be seen as two units of operations. Not only that, operations
in between the two units, i.e., the superposition of 1 and 0, can also be
realised using two valleys. Thus, these valleys have potential to encode,
process, and store quantum information at room temperature – A holy grail
for quantum computing.
In this talk, I will discuss how valley-selective excitation in graphene
with zero bandgap can be achieved by an all-optical means. Ultrashort
laser pulses are employed to obtain a desire control over valley
polarisation. By tailoring the waveforms of the laser pulses to the
symmetry of the graphene’s sub-lattice, first I will demonstrate that it
is possible to induce and read valley polarization in graphene -- a
medium where light-driven valleytronics was thought to be impossible. In
the later part of this talk, I will show a coherent protocol to initiate
valley-selective excitation, de-excitation and switch the excitation to
another valley within tens of femtoseconds. Coherent switching of
electronic excitation from one valley to another on a timescale faster
than the valley decoherence is quintessential for valleytronics-based
emerging quantum technologies at ambient conditions.
ABOUT THE SPEAKER:
Affiliation of the Speaker :
Department of Physics Indian Institute of Technology Bombay Mumbai