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Optical Signatures of Dynamical Excitonic Condensates

Alexander Osterkorn1,*, Yuta Murakami2, Tatsuya Kaneko3, Zhiyuan Sun4, Andrew J. Millis5,6, and Denis Golež1,7

  • 1Jožef Stefan Institute, SI-1000 Ljubljana, Slovenia
  • 2Center for Emergent Matter Science, RIKEN, Wako, Saitama 351-0198, Japan
  • 3Department of Physics, Osaka University, Toyonaka, Osaka 560-0043, Japan
  • 4State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, People’s Republic of China
  • 5Department of Physics, Columbia University, 538 West 120th Street, New York, New York 10027, USA
  • 6Center for Computational Quantum Physics, Flatiron Institute, 162 5th Avenue, New York, New York 10010, USA
  • 7Faculty of Mathematics and Physics, University of Ljubljana, 1000 Ljubljana, Slovenia

  • *Contact author: alexander.osterkorn@ijs.si
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Phys. Rev. Lett. 135, 106902 – Published 5 September, 2025

DOI: https://doi.org/10.1103/58r8-cpzn

Abstract

We theoretically study dynamical excitonic condensates occurring in bilayers with an imposed chemical potential difference and in photodoped semiconductors. We show that optical spectroscopy can experimentally identify phase-trapped and phase-delocalized dynamical regimes of condensation. In the weak-bias regime, the trapped dynamics of the order parameter’s phase lead to an in-gap absorption line at a frequency almost independent of the bias voltage, while, for larger biases, the frequency of the spectral feature increases approximately linearly with bias. In both cases, there is a pronounced second-harmonic response. Close to the transition between the trapped and freely oscillating states, we find a strong response upon application of a weak electric probe field, compare the results to those found in a minimal model description for the dynamics of the order parameter’s phase, and analyze the limitations of the latter.

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Phys. Rev. Lett. 135, 106902– Published 5 September, 2025
  • Received 11 November 2024
  • Accepted 5 August 2025
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