Coherent control of orbital wavefunctions in the quantum spin liquid $Tb_{2}Ti_{2}O_{7}$

TL;DR

This paper demonstrates the coherent control of orbital wavefunctions in the quantum spin liquid material $Tb_{2}Ti_{2}O_{7}$ using resonant THz pulses, revealing a new method for ultrafast manipulation of quantum states in complex materials.

Contribution

It introduces a novel approach to coherently manipulate orbital wavefunctions in a strongly correlated quantum spin liquid material.

Findings

Resonant THz pulses create superpositions of Tb 4f states.

Macroscopic oscillating magnetic dipoles are observed.

Quantum coherence persists before dephasing due to magnetic interactions.

Abstract

Resonant driving of electronic transitions with coherent laser sources creates quantum coherent superpositions of the involved electronic states. Most time-resolved studies have focused on gases or isolated subsystems embedded in insulating solids, aiming for applications in quantum information. Here, we demonstrate coherent control of orbital wavefunctions in pyrochlore $Tb_{2}Ti_{2}O_{7}$, which forms an interacting spin liquid ground state. We show that resonant excitation with a strong THz pulse creates a coherent superposition of the lowest energy Tb 4f states before the magnetic interactions eventually dephase them. The coherence manifests itself as a macroscopic oscillating magnetic dipole, which is detected by ultrafast resonant x-ray diffraction. The induced quantum coherence demonstrates coherent control of orbital wave functions, a new tool for the ultrafast manipulation and investigation of quantum materials.