Beyond conventional Landau scaling in tuning-induced ferroelectric transitions

Recent experiments on quantum paraelectrics have reported deviations from the conventional Landau scaling in tuning-induced ferroelectric transitions, which were attributed to quantum fluctuations modifying the critical exponent. Here, we demonstrate theoretically that the observed scaling anomaly can be quantitatively captured without invoking additional zero-point effects, provided that the bosonic nature of thermal polarization fluctuations is properly incorporated. Based on bosonic thermal statistics, we derive a refined thermal scaling for tuning-induced ferroelectric transitions in quantum paraelectrics, which departs qualitatively from the simple power-law behavior predicted by Landau theory. Applying this scaling to strained SrTiO3, Ca-doped SrTiO3, Nb-doped KTaO3, Ge-doped PbTe, and pressure-tuned TTF-QBr2I2, we obtain quantitative agreement with experimental measurements, accurately capturing the tuning dependence of the ferroelectric transition temperature over a wide range of tuning parameters. Our results identify thermal bosonic excitations as the dominant mechanism underlying the deviation from the conventional Landau scaling and provide a unified and experimentally testable description of tuning-induced phase transitions in bosonic quantum-critical systems.