ELFT HÍRADÓ

[Janos Asboth <asboth.janos AT ttk.bme.hu>]

Meghívó

BME Elméleti Fizika Szeminárium,

nov. 15. péntek 10h15,
1111 Budapest, Budafoki út 8., BME F I. 1. emelet, Schay terem

Alexander Osterkorn (Jožef Stefan Institute, Ljubljana):
Optical signatures of dynamical excitonic condensates

Excitons, or bound electron-hole pairs, can condense into an excitonic
insulator state, similarly to Cooper pairs in superconductors. A
non-equilibrium carrier concentration, such as the one transiently induced
by photo-doping or sustained by a tuneable bias voltage in bilayers, can
create a dynamical excitonic insulator state, yet proving phase coherence
in such setups remains challenging.
We examine the condensate phase behavior theoretically and show that
optical spectroscopy can distinguish between phase-trapped and
phase-delocalized dynamical regimes. In the weak-bias regime, trapped phase
dynamics result in an in-gap absorption peak nearly independent of bias
voltage, while at higher biases its frequency increases approximately
linearly.
Both regimes exhibit pronounced second harmonic responses. In the large
bias regime, the response current grows strongly under the application of a
weak electric probe leading to negative weight in the optical response,
which we analyze relative to predictions from a minimal model for the
phase. This work opens new avenues for experimentally probing coherence in
excitonic condensates and the detection of their dynamical regimes.

Reference: arxiv.org/abs/2410.22116

Minden érdeklődőt szeretettel várunk.
Asbóth János,
 szemináriumi koordinátor