A structural hysteresis in the charge density wave transition of 1T-TaS2

TL;DR

This paper investigates the structural hysteresis in the charge density wave transition of 1T-TaS2, revealing local distortions and stacking order changes that underpin the resistivity hysteresis observed during phase transitions.

Contribution

It uncovers the structural origins of hysteresis in 1T-TaS2's CDW transition, linking local distortions and stacking order to resistivity behavior.

Findings

Structural hysteresis is caused by Ta displacements and S distortions.

Superstructure stacking order weakens with warming and disappears in ICDW.

Resistivity hysteresis is rooted in structural distortions.

Abstract

In quasi-two-dimensional 1T-TaS2, a charge density wave (CDW) prototype, the transition occurs in two steps, from incommensurate (ICDW) and nearly commensurate (NCCDW) and from NCDW to commensurate (CCDW), locked in the resistivity step-wise behavior. The hysteresis observed in the resistivity across the NCDW-to-CCDW transition has roots to a structural hysteresis, where local distortions of the sqrt(13)a x sqrt(13)a superstructure are revealed by neutron and X-ray diffraction. The structural hysteresis is due to faulty stars of David (SODs) because of Ta displacements away from the perfect trigonal geometry as well as out of plane S distortions. Furthermore, the superstructure exhibits a 3co layer stacking order that weakens on warming and fully disappears in the ICDW state.