Non-heating Floquet systems
Typ
Examensarbete för masterexamen
Program
Physics and astronomy (MPPAS), MSc
Publicerad
2020
Författare
Högberg, Michael
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
In the last decade there has been immense progress in experimentally realizing periodically
driven, so-called Floquet systems, that exhibit topological features. However,
there is an expectation that most Floquet systems heat up with time, absorbing
energy from the drive, and thus evolve towards a featureless state in which all local
correlations are fully random. In this thesis it is shown that it is theoretically possible
to have a Floquet system which do not heat up, giving that any existing local
correlations could be infinitely long lived. In other words, this shows that interesting
physical phenomenon, such as a non-trivial topological phase, could in principal be
present in a Floquet system for infinitely long times. The Floquet model which exhibits
this non-heating phase is that of a square-wave drive where the Hamiltonian
of the system jumps between an arbitrarily chosen CFT and a sine-square deformation
of the same CFT. This model was first proposed in 2018 by Wen and Wu in
Ref. [1]. We present in this thesis a generalization of the Floquet system proposed
by Wen and Wu – we still use the same square wave drive but now with what we
call a sine-k-square deformation, hence a deformation of higher harmonics. With
this generalization we also find the interesting property of a non-heating phase for
certain values of the driving parameters. Furthermore, we find that the value of k in
the sine-k-squared deformation that we propose has some rather important implications
for which driving parameter values we can have in a non-heating phase: The
region of the driving parameter values which gives the non-heating phase shrinks
with growing k.
Beskrivning
Ämne/nyckelord
CFT , Floquet theory , Floquet heating problem , sine-square deformation , sine-k-square deformation