The multi-photon induced Fano effect

K. L. Litvinenko,Zhiming Huang,C. R. Pidgeon,N. V. Abrosimov,Nguyen H. Le,B. N. Murdin,Y. Andreev,B. Redlich

doi:10.1038/s41467-020-20534-0

Abstract

The ordinary Fano effect occurs in many-electron atoms and requires an autoionizing state. With such a state, photo-ionization may proceed via pathways that interfere, and the characteristic asymmetric resonance structures appear in the continuum. Here we demonstrate that Fano structure may also be induced without need of auto-ionization, by dressing the continuum with an ordinary bound state in any atom by a coupling laser. Using multi-photon processes gives complete, ultra-fast control over the interference. We show that a line-shape index q near unity (maximum asymmetry) may be produced in hydrogenic silicon donors with a relatively weak beam. Since the Fano lineshape has both constructive and destructive interference, the laser control opens the possibility of state-selective detection with enhancement on one side of resonance and invisibility on the other. We discuss a variety of atomic and molecular spectroscopies, and in the case of silicon donors we provide a calculation for a qubit readout application.

Highlights

The ordinary Fano effect occurs in many-electron atoms and requires an autoionizing state
Can the Fano resonance be controlled by the coupling beam intensity, the discrete state need not be auto-ionizing, allowing continuum structure to be obtained in principle for any atom at any point in the continuum
The interaction, V, between the discrete state and the continuum, dresses jci with jai, and the phase of this mixture changes sign either side of jai producing constructive and destructive interference when probed with an optical dipole transition with perturbation interaction, D

Summary

Introduction

The ordinary Fano effect occurs in many-electron atoms and requires an autoionizing state. Very exciting and flexible possibilities for control occur if the coupling interaction with the continuum is instead optically induced[15] In this situation, can the Fano resonance be controlled by the coupling beam intensity, the discrete state need not be auto-ionizing, allowing continuum structure to be obtained in principle for any atom at any point in the continuum. An example is the jai 1⁄4 j2s; 2pi state in helium[1] and its semiconductor analogue the double donor[5], which can be produced with a single photon excitation from the jgi 1⁄4 j1s; 1si ground state (it is dipole allowed) and can spontaneously decay to jkωi 1⁄4 j1s; ci, which comprises one electron in the 1s state and one in the continuum (i.e., one relaxing and one being ejected) This decay is called auto-ionization, because it costs no extra energy (jai is above the oneelectron continuum edge) and the interaction that produces it is a static configuration interaction such as the internal electron–. The excited states of hydrogenic atoms are bound, i.e., they are not auto-

Methods

Results

Conclusion