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Publication: Dynamics of a single exciton in strongly correlated bilayers

The extended paper on the properties of a single exciton, following up on my earlier Europhys Lett, is accepted and published in the New Journal of Physics.

Title: Dynamics of a single exciton in strongly correlated bilayers

Abstract: We formulated an effective theory for a single interlayer exciton in a bilayer quantum antiferromagnet, in the limit when the holon and doublon are strongly bound onto one interlayer rung by the Coulomb force. Upon using a rung linear spin-wave approximation of the bilayer Heisenberg model, we calculated the spectral function of the exciton for a wide range of the interlayer Heisenberg coupling α = J⊥/Jz. In the disordered phase at large α, a coherent quasi-particle peak appears, representing free motion of the exciton in a spin singlet background. In the Néel phase, which applies to more realistic model parameters, a ladder spectrum arises due to Ising confinement of the exciton. The exciton spectrum is visible in measurements of the dielectric function, such as c-axis optical conductivity measurements.

Reference: Louk Rademaker, Kai Wu and Jan Zaanen, New J. Phys. 14, 083040 (2012).

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Publication: The dynamical frustration of interlayer excitons delocalizing in bilayer quantum antiferromagnets

The paper on the properties of a single exciton is accepted and published in the January issue of Europhysics Letters! (See the completely different arXiv version here.)

Title: The dynamical frustration of interlayer excitons delocalizing in bilayer quantum antiferromagnet

Abstract: Using the self-consistent Born approximation we study the delocalization of interlayer excitons in the bilayer Heisenberg quantum antiferromagnet. Under realistic conditions we find that the coupling between the exciton motion and the spin system is strongly enhanced as compared to the case of a single carrier, to a degree that it mimics the confinement physics of carriers in Ising spin systems. We predict that the “ladder spectrum” associated with this confinement physics should be visible in the c-axis exciton spectra of insulating bilayer cuprates such as YBa2Cu3O6. Our discovery indicates that finite density systems of such excitons should show very rich physical behavior.

Reference: Louk Rademaker, Kai Wu, Hans Hilgenkamp and Jan Zaanen, EPL 97, 27004 (2012).

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Publication: Prediction of quantization of magnetic flux in double-layer exciton superfluids

My work on flux quantization in exciton superfluids finally culminated into a paper published in PRB. A preprint version (which is slightly different) can be found on the arXiv.

Title: Prediction of quantization of magnetic flux in double-layer exciton superfluids

Abstract: Currently, there is no way to detect unambiguously the possible phase coherence of an exciton condensate in an electron-hole double layer. Here, we show that, despite the fact that excitons are charge neutral, the double-layer exciton superfluid exhibits a diamagnetic response. In devices with specific circular geometry, the magnetic-flux threading between the layers must be quantized in units of h/e χm, where χm is the diamagnetic susceptibility of the device. We discuss possible experimental realizations of the predicted unconventional flux quantization.

Reference: Louk Rademaker, Jan Zaanen and Hans Hilgenkamp, Phys. Rev. B 83, pp. 012504 (2011)