Spectroscopic signatures of persistent exciton condensation in a bulk magnetic topological insulator
Abstract
Exciton condensates are long-sought correlated quantum states arising from macroscopic coherence of bound electron-hole pairs. Although equilibrium and transient excitonic states have been reported in several material platforms, direct evidence for a light-induced exciton condensate state has been challenging to achieve as an intrinsic property of a bulk quantum material. Here, we use time- and angle-resolved photoemission spectroscopy to investigate long-lived photoexcited carriers in the intrinsic magnetic topological insulator MnBi2Te4 with the chemical potential tuned to the topological surface state by Sb substitution. Following optical excitation, we observe the delayed emergence of a transient state whose formation coincides with depopulation of the bulk conduction band and whose lifetime extends to the microsecond timescale. The quasiparticle dispersion exhibits a pronounced flattening and develops a Mexican-hat-like profile. These spectral signatures are consistent with the formation of a metastable excitonic condensate state. Our results establish magnetic topological insulators as a promising platform for investigating long-lived photoinduced many-body states and their interplay with topology and magnetism.
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BibTeX
@misc{majchrzak2026spectroscopic,
title = {{Spectroscopic signatures of persistent exciton condensation in a bulk magnetic topological insulator}},
author = {Paulina Majchrzak and Chakradhar Sahoo and Manuel Tuniz and Wibke Bronsch and Denny Puntel and Federico Cilento and Xing-Chen Pan and Jakob Kjærulff Svaneborg and Yong P. Chen and Søren Ulstrup},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.27079},
eprint = {2609.27079},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.27079},
}
RIS
TY - UNPB
TI - Spectroscopic signatures of persistent exciton condensation in a bulk magnetic topological insulator
AU - Paulina Majchrzak
AU - Chakradhar Sahoo
AU - Manuel Tuniz
AU - Wibke Bronsch
AU - Denny Puntel
AU - Federico Cilento
AU - Xing-Chen Pan
AU - Jakob Kjærulff Svaneborg
AU - Yong P. Chen
AU - Søren Ulstrup
PY - 2026
DA - 2026/09/22
PB - arXiv
DO - 10.48550/arxiv.2609.27079
UR - https://arxiv.org/abs/2609.27079
AB - Exciton condensates are long-sought correlated quantum states arising from macroscopic coherence of bound electron-hole pairs. Although equilibrium and transient excitonic states have been reported in several material platforms, direct evidence for a light-induced exciton condensate state has been challenging to achieve as an intrinsic property of a bulk quantum material. Here, we use time- and angle-resolved photoemission spectroscopy to investigate long-lived photoexcited carriers in the intrinsic magnetic topological insulator MnBi_2Te_4 with the chemical potential tuned to the topological surface state by Sb substitution. Following optical excitation, we observe the delayed emergence of a transient state whose formation coincides with depopulation of the bulk conduction band and whose lifetime extends to the microsecond timescale. The quasiparticle dispersion exhibits a pronounced flattening and develops a Mexican-hat-like profile. These spectral signatures are consistent with the formation of a metastable excitonic condensate state. Our results establish magnetic topological insulators as a promising platform for investigating long-lived photoinduced many-body states and their interplay with topology and magnetism.
ER -