Significant inverse topological caloric effect induced by topological multicriticality

Recent attention has focused on the BDI symmetry class, which exhibits gapless topological quantum phase transitions (TQPTs) between critical phases along a critical line, arising from the interplay between topology and criticality with edge modes persisting at criticality. Here, we generalize this unconventional TQPT to an extended Su-Schrieffer-Heeger (SSH) model with broken time-reversal symmetry, belonging to the AIII symmetry class. This gapless topological criticality is characterized by a critical winding number with half integer and quantized jump, alongside a Grüneisen ratio (GR) displaying critical ±T⁻¹ divergence and symmetric peak-dip structures. Furthermore, we propose that multicriticality-enhanced topological caloric effects (TCEs) offer a promissing alternative to the conventional magnetic refrigeration for quantum devices. By tuning topological parameters along the critical line, we demonstrate a significant inverse TCE (ITCE) near the multicritical point at low temperatures, featuring large isothermal entropy change, adiabatic temperature change and high efficiency factor. This pronounced ITCE could enable ultralow temperature cooling, advancing both the thermodynamic charaterization of gapless TQPT and cryofree quantum referigeration for quantum computing environments.