ELFT HÍRADÓ

[Andras Palyi <palyi AT mail.bme.hu>]

Dear Colleagues, 
 
Next Monday the BME Exotic Quantum Phases seminar series continues with this 
talk:
 
Speaker: Simon Körber (Würzburg)
Title: Interacting topological frequency converter
Abstract: see below
Reference: 
https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.2.022023 
<https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.2.022023>
 
Time: Feb 15, 14:15 Budapest time
Location: online in Teams
 
About the speaker: Simon is theoretical physicist with an expertise in 
correlated electron systems, Shiba states in superconductors, and topological 
features of non-equilibrium quantum systems. Currently he is a 3rd-year PhD 
student in Würzburg, in the group of Björn Trauzettel.
 
Link to join the meeting in Teams:
https://teams.microsoft.com/l/meetup-join/19%3a98c537f3ff3a433983cc04579e4603af%40thread.tacv2/1613129497237?context=%7b%22Tid%22%3a%226a3548ab-7570-4271-91a8-58da00697029%22%2c%22Oid%22%3a%22f8b27e90-dbca-4bb5-813c-d6415577ec35%22%7d
 
<https://teams.microsoft.com/l/meetup-join/19%3a98c537f3ff3a433983cc04579e4603af%40thread.tacv2/1613129497237?context=%7b%22Tid%22%3a%226a3548ab-7570-4271-91a8-58da00697029%22%2c%22Oid%22%3a%22f8b27e90-dbca-4bb5-813c-d6415577ec35%22%7d>

Best regards,
Andras Palyi
 
= = = 
 
Abstract:
 
Non-equilibrium quantum systems host a plethora of topological phenomena. A 
topological property of quantum dynamics can be related to the effective 
dimensional extension of the system by time-periodic drives. Following this 
line of reasoning, it has been shown that a two-level system coupled to two 
circularly polarized drives can mediate a frequency conversion between the 
two fields that happens at a topologically quantized rate [1]. In this talk, 
we will address two types of questions that naturally arise for this kind of 
quantum system.

The first is whether interaction can change the topological features in the 
dynamically-induced synthetic dimension. We positively answer this question 
by adding spin-spin interactions to the prototypical model of the topological 
frequency converter [2]. We demonstrate that the interplay of interaction and 
synthetic dimension gives rise to striking topological phenomena that have no 
counterpart in the non-interacting regime. Remarkably, these features already 
appear for the minimal case of two interacting spins, and can result into an 
enhancement of frequency conversion as a direct manifestation of the 
correlated topological response.

Given a realization of the topological frequency converter by an externally 
driven spin qubit, the second question that arises is how environmental 
effects may affect the dynamical topological response. By studying a 
quasiperiodically driven central spin model, we demonstrate that the coupling 
to the surrounding (nuclear) spin bath can lead to an amplification of the 
frequency conversion that is proportional to the number of (nuclear) spins of 
the host material.

[1] I. Martin, G. Refael, and B. Halperin, Phys. Rev. X 7, 041008 (2017).

[2] S. Körber, L. Privitera, J. C. Budich, and B. Trauzettel, Phys. Rev. 
Research 2, 022023(R) (2020).