Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session Y59: Dirac and Weyl Semimetals: Theory I
8:00 AM–10:48 AM,
Friday, March 18, 2022
Room: Hyatt Regency Hotel -DuSable AB
Sponsoring
Unit:
DCMP
Chair: Angkun Wu, Rutgers University
Abstract: Y59.00003 : A generic approach to extract geometry from non-adiabatic (gap-closing) processes and its consequences: geometric pumping and dephasing at topological phase transitions in topological insulators or semi-metals.*
8:24 AM–8:36 AM
Presenter:
Boqun Song
(Iowa State University)
Authors:
Boqun Song
(Iowa State University)
Jonathan Smith
(Iowa State University)
Liang Luo
(Iowa State University)
JIGANG Wang
(Iowa State University)
Our first result (Song 2021) is to show Berry’s framework (and its development) is not the unique one to incorporate geometry. In fact, parallel transport or local curvatures are dispensable. Our scheme relies on making quantum evolution mimic classical trajectories via a measure-preserving formalism (MPF). Measure preservation means a conservative system’s volume in phase space {p,q} is constant during evolution, known as the Liouville theorem. However, its quantum counterpart, Wigner flow, is compressible, which depreciates usage and poses a long-pending question: if MPF can be rigorously constructed and significantly used in quantum scenarios.
The second result is about an observable, inter-band pumping, namely geometric pumping. Its rate purely depends on an angle parameter, which, in certain in- stances, is linked to Z2. Since the pumping is for bulk, it challenges the wisdom that Z2 only implies sur- face/interface, known as bulk-edge correspondence. It relies on the flipping of Z2 (not which state of Z2) thus is a genuine consequence of topological phase transitions (TPT). We set out from a spin model to introduce a generic MPF, with which pumping rates and conditions are proved. Meanwhile, rational/irrational numbers are giving subtle influence. This work helps account for recent experiments on TPT in ZrTe5 (Luo 2021, Vaswani 2020).
*This work was supported by the Ames Laboratory, the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division under contract No. DEAC02-07CH11358. Terahertz instrument was supported in part by the National Quantum Information Science Research Center; Superconducting Quantum Materials Systems Centers.
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