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BEGIN:VEVENT
DTSTAMP:20261026T114909Z
LAST-MODIFIED:20190918T133221Z
DTSTART:20190925T200000Z
DTEND:20190925T210000Z
UID:event2189@bu.edu
URL:http://physics.bu.edu/internal/events/show/2189
SUMMARY:Flow equation approach to Floquet systems
DESCRIPTION:Featuring Michael Vogl\, Northeastern University\n\nPart of the
	 Biophysics/Condensed Matter Seminar Series.\n\nRecent years have seen rapi
	d progress in our understanding of periodically driven quantum systems. Eve
	n so many of the available theoretical techniques are still perturbative in
	 nature or limited to certain classes of quantum systems - such as non-inte
	racting or few site interacting systems. In this talk I will present a quit
	e general theoretical method [1] to generate a highly accurate time-indepen
	dent Hamiltonian governing the finite-time behavior of a time-periodic syst
	em. The method exploits infinitesimal unitary transformation steps\, from w
	hich renormalization group-like flow equations are derived to produce the e
	ffective Hamiltonian. The method has a range of validity reaching into freq
	uency and driving strength regimes that are usually inaccessible via high f
	requency expansions. I will demonstrate how this approach can be applied to
	 periodically driven many-body Hamiltonians. Using exact diagonalization as
	 a benchmark we find that it offers an improvement over the more well-known
	 Floquet-Magnus expansion. I will also demonstrate how the method is connec
	ted to an analog of Hamilton-Jacobi theory [2] and how this allows us to re
	late different common approximation techniques for time ordered exponential
	s. \nIf time permits I will also briefly discuss lessons we learnt from our
	 most recent work [3] on effective Hamiltonians for the low frequency\, wea
	k driving regime.\n[1] M. Vogl\, P. Laurell\, A. D. Barr\, G. A. Fiete\, "A
	 flow equation approach to periodically driven systems"\, Phys. Rev. X 9\, 
	021037 (2019). [2] M. Vogl\, P. Laurell\, A. D. Barr\, G. A. Fiete\, "Analo
	gue of Hamilton-Jacobi theory for the time-evolution operator"\, Phys. Rev.
	 A 100\, 012132 (2019) [3] M. Vogl\, M. Rodriguez-Vega\, G. A. Fiete\, "Eff
	ective Floquet Hamiltonian in the low-frequency regime"\, arXiv:1909.04263
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
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