Quantum Critical Phenomena in Compressible Displacive Ferroelectric
Proceedings of the National Academy of Sciences of USA
National Academy of Sciences
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Saxena, S. (2020). Quantum Critical Phenomena in Compressible Displacive Ferroelectric. Proceedings of the National Academy of Sciences of USA https://doi.org/10.1073/pnas.1922151117
The dielectric and magnetic polarizations of quantum paraelectrics and paramagnetic materials have in many cases been found to initially increase with increasing thermal disorder and hence, exhibit peaks as a function of temperature. A quantitative description of these examples of “order-by-disorder” phenomena has remained elusive in nearly ferromagnetic metals and in dielectrics on the border of displacive ferroelectric transitions. Here, we present an experimental study of the evolution of the dielectric susceptibility peak as a function of pressure in the nearly ferroelectric material, strontium titanate, which reveals that the peak position collapses toward absolute zero as the ferroelectric quantum critical point is approached. We show that this behavior can be described in detail without the use of adjustable parameters in terms of the Larkin–Khmelnitskii–Shneerson–Rechester (LKSR) theory, first introduced nearly 50 y ago, of the hybridization of polar and acoustic modes in quantum paraelectrics, in contrast to alternative models that have been proposed. Our study allows us to construct a detailed temperature–pressure phase diagram of a material on the border of a ferroelectric quantum critical point comprising ferroelectric, quantum critical paraelectric, and hybridized polar-acoustic regimes. Furthermore, at the lowest temperatures, below the susceptibility maximum, we observe a regime characterized by a linear temperature dependence of the inverse susceptibility that differs sharply from the quartic temperature dependence predicted by the LKSR theory. We find that this non-LKSR low-temperature regime cannot be accounted for in terms of any detailed model reported in the literature, and its interpretation poses an empirical and conceptual challenge.
Jesus and Trinity Colleges of the University of Cambridge; the Engineering and Physical Sciences Research Council; the Conselho Nacional das Fundações Estaduais de Amparo à Pesquisa Newton Fund; the Royal Society; Institute for High Technology KAZATOMPROM, Kazakhstan; and United Kingdom Research and Innovation Global Challenges Research Fund COMPASS Grant ES/P010849/1. G.G.L. acknowledges the support of the National Council for Scientific and Technological Development, Brazil/Science without Borders Program, Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro, Brazil. Part of the work was carried out with financial support from the Ministry of Education and Science of the Russian Federation in the framework of Increase Competitiveness Program of NUST MISiS K2-2017-024, implemented by a governmental decree dated March 16, 2013, Number 211.
Engineering and Physical Sciences Research Council (EP/E00489X/1)
Economic and Social Research Council (ES/P010849/1)
ESRC (via University of Kent) (ES/P010849/1)
External DOI: https://doi.org/10.1073/pnas.1922151117
This record's URL: https://www.repository.cam.ac.uk/handle/1810/304406
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