Angular-Momentum Transfer Mediated by a Vibronic-Bound-State

The notion that phonons can carry pseudo-angular momentum has many major consequences, including topologically protected phonon chirality, Berry curvature of phonon band structure, and the phonon Hall effect. When a phonon is resonantly coupled to an orbital state split by its crystal field environment, a so-called vibronic bound state forms. Here, a vibronic bound state is observed in NaYbSe2, a quantum spin liquid candidate. In addition, field and polarization dependent Raman microscopy is used to probe an angular momentum transfer of Delta Jz = +/- PLANCK CONSTANT OVER TWO PI between phonons and the crystalline electric field mediated by the vibronic bound stat. This angular momentum transfer between electronic and lattice subsystems provides new pathways for selective optical addressability of phononic angular momentum via electronic ancillary states. Angular momentum transfer between phonons and the crystal electric field in a candidate quantum spin liquid is observed with polarization- and magnetic-field-dependent Raman microscopy. These results provide a new framework for selective optical addressability of phononic angular momentum via electronic, spin, and orbital degrees of freedom in emerging quantum materials.image