Quantum Musical Chairs*

We present a model that describes how Pauli quantum degeneracy suppresses photoemission of electrons using ultrafast lasers. This is expected to happen when a few (N) electrons are emitted in such a narrow interval in space and time that it approaches limits set by the uncertainty principle. However, our model also predicts a suppression in the emission of N electrons due to the Pauli degeneracy when N>>1. This regime is different than where coincidence searches [1,2,3] for free electron degeneracy were done. Not only is N>>1, but also D<<1, where D=N×(V_c/V) is the quantum degeneracy, V is the volume the electrons are emitted in, and V_c is the coherence volume. The idea is analogous with the musical chairs game wherein a single person (electron) occupies a chair (coherence volume) and subsequent people (electrons) landing in the same chair (volume) are not permitted there. Statistically, the number of people that can occupy a chair is diminished by roughly 50% when N~sqrt(V/V_c). We propose experiments that can bring out the phenomenon of free electron Pauli blockade and differentiate it from Coulomb repulsion for the regime N>>1. Given that Coulomb repulsion has recently been observed in correlation experiments for few electron pulses, N~1 [4,5,6], this is our next main goal. We put forward a list of electron sources that are currently active for experiments that may have favorable parameters to probe this new regime for free electrons. We further discuss the instrumental error introduced by crosstalk between coincidence measurement circuits and introduce a method to isolate and remove these effects in the data analysis [7].

[1] Kuwahara M. et al, Phys. Rev. Lett. 126, 125501 (2021). 

[2] Kiesel, H., Renz, A. & Hasselbach, F. Nature 418, 392–394 (2002). 

[3] Kodama, T., Osakabe, N. & Tonomura, A. Phys. Rev. A 83, 063616 (2011). 

[4] S. Keramati, W. Brunner, T. J. Gay, and H. Batelaan, Phys. Rev. Lett. 127, 180602 (2021). 

[5] S. Meier, J. Heimerl, and P. Hommelhoff, Nature Physics 19, 1402 (2023) 

[6] R. Haindl, et al., Nature Physics 19, 1410 (2023). 

[7] A. Krishnan, R. Puente, M.A.H.B. Md Yusoff, S. Keramati and H. Batelaan, arXiv:2411.13863 (2024).