Effect of Dark Energy in Geometrothermodynamics and Phase Transitions of Regular Bardeen AdS Black Hole

Abstract: We investigate thermodynamics and geometrothermodynamics of regular Bardeen AdS black hole with quintessence. The thermodynamics of the black hole is studied using temperature-entropy ($T-S$) , Pressure-Volume ($P-v$), and Gibbs energy plots, which indicate a critical behaviour.This is also confirmed from the divergence of specific heat against entropy, which shows a second-order phase transition. Moreover, we observe that the quintessence state parameter $\omega$ shifts the transition point to lower entropy values. Using the concept of thermodynamic Ruppeiner and Weinhold geometry, we calculated the thermodynamic curvature scalar $R_R$ and $R_W$ in the quintessence dark energy regime ($\omega =-2/3$). While these curvature scalars enable us to identify the critical behavior, they do not show divergence at the phase transition points observed in specific heat studies. To resolve this puzzle, we have adopted the method of geometrothermodynamics proposed by Hernando Quevedo. Choosing a Legendre invariant Quevedo metric, the curvature scalar $R_Q$ shows singularity at the same point as seen in the specific heat divergence.