Static and Ensemble-Dependent Thermodynamics of the Strain-Induced Parity Anomaly in Gapped Graphene

Abstract

A static deformation of graphene can act on its Dirac electrons as a valley-odd magnetic field. In sublattice-gapped graphene this field makes the two valleys add in the parity-odd response rather than cancel. We derive the equilibrium thermodynamics of this effect and separate it from the finite-frequency transport response. At fixed electrochemical potential, reversing the pseudomagnetic field removes every nonzero pseudo-Landau level in the continuum theory. The remaining grand-potential difference is fixed by the spectrally asymmetric zeroth level. The static charge response is a thermally broadened plateau confined to the gap and has no metallic $m/|\mu |$ tail. Near a band edge, pseudofield reversal transfers $\mathrm{B}\ln 2$ of entropy per unsplit zero-mode state in the low-temperature window. The fixed-$\mu$ heat capacity has two side lobes per edge and a universal peak $0.439229D_B{k}_{\mathrm{B}}$. We then formulate a definite constant-gate-voltage circuit and show that the measured sheet heat capacity depends on the electrical boundary condition. The full massive-Dirac density of states and an exact finite-field pseudo-Landau-level calculation give the same gate crossover in their common limit. At fixed carrier number, the low-temperature edge value is $-2(\ln 2{)}^2{D}_B{k}_{\mathrm{B}}$, rather than a node. A finite geometric capacitance gives a continuous and experimentally tunable interpolation. Finally, we give a trace-free triaxial strain geometry, a disorder--interaction window, and realistic calorimetric and quantum-capacitance scales. The field-reversal protocol isolates an equilibrium electromechanical anomaly without a real magnetic field.

13 pages, 9 figures