Quantum paraelectricity in the Kitaev quantum spin liquid candidates <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi mathvariant="normal">H</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:mi>LiI</mml:mi><mml:msub><mml:mi mathvariant="normal">r</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>6</mml:mn></mml:msub></mml:mrow></mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi mathvariant="normal">D</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:mi>LiI</mml:mi><mml:msub><mml:mi mathvariant="normal">r</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>6</mml:mn></mml:msub></mml:mrow></mml:math>
K. Geirhos, P. Lunkenheimer, Moritz Blankenhorn, R. R. Claus, Y. Matsumoto, Kentaro Kitagawa, T. Takayama, H. Takagi, I. Kézsmárki, A. Loidl
Abstract
H${}_{3}$LiIr${}_{2}$O${}_{6}$ shows no magnetic order down to lowest temperatures, raising hopes for a true Kitaev spin liquid. Its structure reveals H bonds between honeycomb layers and theory has proposed hydrogen disorder to affect the magnetic exchange. Using dielectric spectroscopy, the authors report here dipolar relaxations in H${}_{3}$LiIr${}_{2}$O${}_{6}$ and D${}_{3}$LiIr${}_{2}$O${}_{6}$, mirroring the dynamics of protons or deuterons within the double-well potentials of the H bonds. Under cooling, thermal activation crosses over into quantum tunneling, establishing a quantum paraelectric state with quasistatic disorder. This supports the realization of the long-pursued Kitaev spin liquid.