Superchiral photons unveil magnetic circular dichroism

S. W. Lovesey, J. T. Collins, S. P. Collins

Research output: Contribution to journalArticle

Abstract

Polarization-dependent photon spectroscopy (dichroism) using signal-enhancing superchiral beams is shown to be sensitive to magnetic properties of the sample, whereas previous investigations explored chargelike electronic properties of chiral samples. In the process of unveiling the potential to observe magnetic circular dichroism (MCD), we underline an affinity between spectroscopies using the Borrmann effect, twisted beams, and superchiral beams. Use of an effective wave vector in a quantum mechanical theory unites the aforementioned spectroscopies and vastly improves our understanding of their advantages. Exploiting an effective wave vector for superchiral beams, natural circular dichroism (NCD) is derived from electric dipole-magnetic dipole (E1-M1) and electric dipole-electric quadrupole (E1-E2) absorption events, and MCD is derived from electric quadrupole-electric quadrupole (E2-E2) absorption. Signal enhancement by superchiral beams is a straightforward gain for the user because NCD and MCD are otherwise precisely the same as for a circularly polarized beam, according to our calculations. An analysis shows that enhancement of E2-E2 is superior to that available for parity-odd events under consideration. Electronic degrees of freedom in all dichroic signals are encapsulated in atomic multipoles that are frequently used in theoretical interpretations of several established experimental techniques.

Original languageEnglish
Article number054428
JournalPhysical Review B
Volume99
Issue number5
DOIs
Publication statusPublished - 1 Feb 2019

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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