Ferroelectric water chains in carbon nanotubes: Creation and manipulation of ordered quantum phases

Systems composed of molecular rotors are promising candidates as quantum devices. In this work, we employ our recently developed density matrix renormalization group approach to study such a rotor system, namely, linear chains of rotating para-water molecules encapsulated in a (6,5)-carbon nanotube. We show that the anisotropic environment provided by the nanotube breaks the inversion symmetry of the chain. This symmetry breaking lifts the degeneracy of the ground state and leads to a splitting between the left- and right-polarized states. In turn, a ferroelectric phase in nanoscopic systems is created, with a polarization that can be switched in a manner analogous to that of a supramolecular qubit. We present results for a few low-lying states and discuss the effect of external electric fields on the energy splitting and the occurrence of a quantum phase transition. Published under an exclusive license by AIP Publishing.

Automated summary

In this work, the density matrix renormalization group approach is used to study the behavior of linear chains of rotating water molecules encapsulated in a carbon nanotube. The anisotropic environment provided by the nanotube breaks the inversion symmetry of the chains, leading to the lifting of ground state degeneracy and splitting between left- and right-polarized states. This results in a ferroelectric phase with a switchable polarization similar to a supramolecular qubit. The effects of external electric fields on energy splitting and quantum phase transition are discussed.