Abstract
We study the importance of interband effects on the orbital susceptibility of three bands α-T3 tight-binding models. The particularity of these models is that the coupling between the three energy bands (which is encoded in the wavefunctions properties) can be tuned (by a parameter α) without any modification of the energy spectrum. Using the gauge-invariant perturbative formalism that we have recently developped[1], we obtain a generic formula of the orbital susceptibility of α-T3 tight-binding models. Considering then three characteristic examples that exhibit either Dirac, semi-Dirac or quadratic band touching, we show that by varying the parameter a and thus the wavefunctions interband couplings, it is possible to drive a transition from a diamagnetic to a paramagnetic peak of the orbital susceptibility at the band touching. In the presence of a gap separating the dispersive bands, we show that the susceptibility inside the gap exhibits a similar dia to paramagnetic transition.
Highlights
The orbital magnetic susceptibility of free electrons was computed long ago by Landau [2] and was found to be diamagnetic
In this work we have studied the importance of interband effects on the orbital susceptibility of three bands α-T3 tight-binding models that were initiated in [7]
The particularity of the α-T3 tight-binding models is that the coupling between the three energy bands can be tuned without any modification of the energy spectrum
Summary
The orbital magnetic susceptibility of free electrons was computed long ago by Landau [2] and was found to be diamagnetic. Peierls extended Landau’s result to the case of a single band tight-binding model. He found a formula for the orbital susceptibility that only depends on the zero-field band energy spectrum. This result already showed that the band structure can have a strong influence on the magnetic response of crystals [3]. The aim of this paper is to present orbital susceptibility results obtained from an exact linear response formula that we recently derived for tight-binding models [1].
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