Multiferroic behavior in elemental selenium below 40 K: effect of electronic topology

Area of Science:

• Condensed Matter Physics
• Materials Science
• Solid-State Chemistry

Background:

• Selenium's quasi-one-dimensional, chiral crystal structure.
• The potential for novel electronic and magnetic properties in low-dimensional materials.

Purpose of the Study:

• To investigate the magnetic and ferroelectric properties of single crystalline Selenium microtubes.
• To understand the underlying mechanisms of observed multiferroic behavior.

Main Methods:

• Synthesis of single crystalline Selenium microtubes.
• Low-temperature magnetic and dielectric measurements.
• Raman spectroscopy.
• First-principles theoretical calculations.
• Landau theory analysis.

Main Results:

• Observation of simultaneous magnetic and ferroelectric order below approximately 40 K.
• A structural transition involving partial chain fragmentation.
• Coupling between magnons, phonons, and electric fields observed via Raman spectroscopy.
• Dielectric constant shows strong magnetic field dependence.
• Theoretical analysis identifies Selenium as a weak topological insulator, with magnetism emerging from spin-polarized surface states.
• Switchable electric polarization along the helical axis due to broken two-fold rotational symmetry.

Conclusions:

• Selenium microtubes exhibit emergent multiferroic properties originating from their topological surface states and chiral bulk structure.
• The observed magnetoelectric couplings can be explained by the interaction of phonons with spin and electric fields.
• This research introduces a new class of topological surface-multiferroics with chiral bulk structures, paving the way for novel electronic device applications.