Boyang Zhao1,Gwan-Yeong Jung2,Huandong Chen1,Guodong Ren2,Shantanu Singh1,Tieyan Chang3,Nick Settineri4,Simon Teat4,Yu-Sheng Chen3,Rohan Mishra2,Jayakanth Ravichandran1
University of Southern California1,Washington University in St. Louis2,Argonne National Laboratory3,Lawrence Berkeley National Laboratory4
Boyang Zhao1,Gwan-Yeong Jung2,Huandong Chen1,Guodong Ren2,Shantanu Singh1,Tieyan Chang3,Nick Settineri4,Simon Teat4,Yu-Sheng Chen3,Rohan Mishra2,Jayakanth Ravichandran1
University of Southern California1,Washington University in St. Louis2,Argonne National Laboratory3,Lawrence Berkeley National Laboratory4
Polarization vortices<sup>1</sup> and skyrmions in epitaxial heterostructures<sup>2</sup> arise from boundary condition engineering of ferroelectric materials. Currently, there are no other physical origin for such polar topological structures. In this work, we report the observation of high order ferroic phase transitions in hexagonal quasi-1D chalcogenides, BaTiX<sub>3</sub> (X = S or Se) <i>via</i> single crystal synchrotron X-ray diffraction. By refining the crystal structure of BaTiX<sub>3</sub> at different temperatures, we observe large displacements of Ti in the TiX<sub>6</sub> octahedral of BaTiX<sub>3</sub> along and across the quasi-1D chains of TiX<sub>3</sub>. BaTiS<sub>3</sub> undergoes a series of symmetry defined TiS<sub>6</sub> dipole ordering from a room temperature <i>P</i>6<sub>3</sub><i>cm</i> ferrielectric phase to a charge-density-wave <i>P</i>3<i>c</i>1 vortex-anti-vortex phase below ~ 250 K and then transforms into a chiral<i> P</i>2<sub>1</sub> phase below ~180 K. While BaTiSe<sub>3</sub> shows distinctive ferroic order than BaTiS<sub>3</sub>, the breaking of the room temperature <i>P</i>31<i>c</i> symmetry is accompanied by emergent correlated disorder ~200K, revealing a longer-range coupling of the ferroic chains in BaTiSe<sub>3</sub>.<br/>The observation of complex ferroic dipolar ordering in BaTiX<sub>3</sub> shows complex high order polar textures can be symmetry driven unlike the ferroelectric heterostructures. We presume the role of multipole interactions as the origin of these emergent polarization textures and note the accessibility of similar structural and electrical characteristics in charge density wave materials such as 1<i>T</i>-TiSe<sub>2</sub><sup>3</sup> and Ta<sub>2</sub>NiSe<sub>5</sub><sup>4</sup>. Our work sets up complex charge density waves with <i>d</i><sup>0</sup> filling as a playground for realizing and understanding quantum polar topologies.<br/> <br/>1. Yadav, A. K. <i>et al.</i> Spatially resolved steady-state negative capacitance. <i>Nature</i> <b>565</b>, 468–471 (2019).<br/>2. Das, S. <i>et al.</i> Observation of room-temperature polar skyrmions. <i>Nature</i> <b>568</b>, 368–372 (2019).<br/>3. Kitou, S. <i>et al.</i> Effect of Cu intercalation and pressure on excitonic interaction in 1 T − TiS e 2. <i>Phys. Rev. B</i> <b>99</b>, 104109 (2019).<br/>4. Nakano, A. <i>et al.</i> Antiferroelectric distortion with anomalous phonon softening in the excitonic insulator Ta 2 NiSe 5. <i>Phys. Rev. B</i> <b>98</b>, 045139 (2018).