# Condensed Matter Seminar: Dr. Manohar Kumar, Aalto University, Finland

Dr. Manohar Kumar

Research Fellow

Department of Applied Physics

Aalto University, Finland

**Particle collider in condensed matter physics for Anyone**

Two-dimensional systems at low temperatures and at high magnetic field, can host exotic particles with elementary excitations carrying fractional charge e* = e/q such as in fractional quantum Hall effect 1 . These exotic particles are called anyons, whose quantum statistics are neither bosonic nor fermionic; instead they are predicted to obey fractional statistics 2 . The fractional charge of these anyons has been studied successfully using low frequency shot noise measurement 3,4 . However, no universal method for sensing them unambiguously exists 5 . Also, clear signature of the fractional statistics remains elusive. Here we exploited the Josephson relation of these anyonic states to determine the fractional charge of excited quasiparticles. The microwave photons emitted by voltage biased anyonic system obey the Josephson relation, like superconducting Josephson junction but with the charge q = e* rather than 2e. This provides direct evidence of fractional charge in fractional quantum Hall effect 6 . Lastly, we also probed the fractional statistics in mesoscopic anyonic collider 7 . Our collision results explicitly extract the quantum phase of \phi = pi/3 for exchange of two anyonic quasiparticles with q = e/3. This is very first smoking gun result on fractional statistics of anyon. This collider geometry could be extended to perform ultimate braiding experiment to realized full potential of special kind of anyon called non-Abelian anyons in topological quantum computation.

References

1. Tsui, D. C., Stormer, H. L. & Gossard, A. C. Two-dimensional magneto-transport in the extreme

quantum limit. Phys. Rev. Lett. 48, 1559–1562 (1982).

2. Leinaas and J. Myrheim, Nuovo Cimento Soc. Ital. Fis.B 37, 1 (1977).

3. de Picciotto, R. et al. Direct observation of a fractional charge. Nature 389, 162–164 (1997).

4. Saminadayar, L., Glattli, D. C., Jin, Y. & Etienne, B. Observation of the e/3 fractionally charged

Laughlin quasiparticles. Phys. Rev. Lett. 79, 2526–2529 (1997).

5. Reznikov, M., de Picciotto, R., Griffiths, T. G., Heiblum, M. & Umansky, V. Observation of

quasiparticles with one-fifth of an electron’s charge. Nature 399, 238–241 (1999).

6. Bisognin, Bartolomei and Kumar et al. Nature Communications, 10, 1708 (2019).

7. Kumar and Bartolomei et al. Science 368, 173 (2020).

Originally published at physics.nd.edu.