Prospects and applications near ferroelectric quantum phase transitions: a key issues review

Abstract

The emergence of complex and fascinating states of quantum matter in the neighborhood of zero temperature phase transitions suggests that such quantum phenomena should be studied in a variety of settings. Advanced technologies of the future may be fabricated from materials where the cooperative behavior of charge, spin and current can be manipulated at cryogenic temperatures. The progagating lattice dynamics of displacive ferroelectrics make them appealing for the study of quantum critical phenomena that is characterized by both space- and time-dependent quantities. In this key issues article we aim to provide a self-contained overview of ferroelectrics near quantum phase transitions. Unlike most magnetic cases, the ferroelectric quantum critical point can be tuned experimentally to reside at, above or below its upper critical dimension; this feature allows for detailed interplay between experiment and theory using both scaling and self-consistent field models. Empirically the sensitivity of the ferroelectric T 's to external and to chemical pressure gives practical access to a broad range of temperature behavior over several hundreds of Kelvin. Additional degrees of freedom like charge and spin can be added and characterized systematically. Satellite memories, electrocaloric cooling and low-loss phased-array radar are among possible applications of low-temperature ferroelectrics. We end with open questions for future research that include textured polarization states and unusual forms of superconductivity that remain to be understood theoretically.

Quantum Ising model on the frustrated square lattice

“…In our case, for a system with an intermediary level of frustration (g * Q < g < g * ), one can observe discontinuous phase transitions in the absence of quantum fluctuations and criticality driven by zero-point fluctuations. Analogous phenomena have been observed in many materials [15], suggesting that our results can provide an interesting additional mechanism, based on competing interactions, for quantum annealed criticality. Underlying signatures of quantum phase transitions are often observed in the thermodynamics properties even at finite temperatures [1,25,26].…”

Charge transport in a polar metal

“…* linxiao@westlake.edu.cn SrTiO 3 single crystals, in contrast to PbTe, can be made stoichiometric enough to be insulating. Proximity to a ferroelectric quantum critical point [11,12] is manifested by a large electric permittivity of SrTiO 3 (ε r > 20000) [13]. As a consequence, this insulator displays a number of intriguing properties [14].…”

Quantum critical points in ferroelectric relaxors: Stuffed tungsten bronze K3Li2Ta5OSmith1, Gardner2, Morrison3 et al. 2018Phys. Rev. Materials2020View full textAdd to dashboardCite

“…However, as the dynamical exponent is 1 for displacive FE rather than 3 for itinerant ferromagnets, the understanding and modeling of their properties are likely to be more complex, since real systems can exceed the upper and lower critical dimensionality [1]. For a QCP to occur, the transition should be driven by quantum fluctuations rather than classical fluctuations, and such quantum fluctuations tend to dominate in a region just above 0 K. Interest in ferroelectric quantum critical points has grown rapidly in the past several years, with emphasis upon perovskites [1,2] and several other materials, including hexaferrites [3][4][5][6] and organic or molecular crystals [7][8][9][10]. However, the QCPs studied thus far do not include many crystal families, and with one recent exception [11], no glassy relaxors.…”

“…In a search for new FE QCP, it is preferable to start with FEs with known transitions near 0 K. KLT and Pb 2 Nb 2 O 7 pyrochlore may have QCP transitions with T c reported as 7 and 15 K respectively; however, to confirm the behavior driving the transition, permittivity versus temperature data are required [5,11,18].…”