Rodriguez Nieva, Joaquin - MIT

Berry’s Phase and Giant Non-Reciprocity in Dirac Quantum Dots

Recently, nanoscale pn-junction rings have been introduced as a vehicle for confinement of electronic states in Dirac materials [1]. Confined states in these Dirac quantum dots arise due to constructive interference of electronic waves incident at the pn junction at oblique angles and inward-reflected from the ring. What special features sets Dirac quantum dots apart from conventional quantum dots? We show [2] that Berry curvature induces a strongly non-reciprocal spectrum of quantum dot resonances under weak magnetic fields. Such effect is maximal for massless Dirac electrons, e.g. graphene, and is manifested in anomalously large splittings of the resonances which are degenerate at B=0 due to time reversal symmetry. This non-reciprocity effect overwhelms the conventional orbital and spin-induced non-reciprocity.

The predicted giant non-reciprocity is readily accessible by Faraday and Kerr optical rotation measurements as well as by scanning tunneling spectroscopy.

[1] Zhao, et al., Science 348,672(2015).

[2] JRN and L. S. Levitov, arXiv:1508.06609.