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SYEC: Symposium Exact-exchange and hybrid functionals meet quasiparticle energy calculations

SYEC 2: Exact-exchange and hybrid functionals meet quasiparticle energy calculations II

SYEC 2.4: Talk

Thursday, February 28, 2008, 14:45–15:00, A 053

Fingerprints of discontinuity in the exchange-correlation energy functional in the subband electronic structure of semiconductor quantum wells — •César R. Proetto and Santiago Rigamonti — Centro Atómico Bariloche and Instituto Balseiro, S. C. de Bariloche, Argentina

One of the basic properties of exact Density Functional Theory, is the derivative discontinuity of the exchange-correlation (xc) energy functional, as the number of electrons in an atom, molecule, or solid changes from N to N+1, with N representing the total number of electrons in a closed shell (atoms and molecules), or in a filled band (semiconductors and insulators). Continuum approximations to the xc energy functional, fail to produce the correct value for this discontinuity, resulting in an important underestimation of the fundamental gap of most semiconductors and insulators. Using an ab initio generated xc functional, which includes exchange exactly and correlation in an exact partial way, we will discuss how this derivative discontinuity arise naturally in the subband spectra of semiconductor quantum wells, each time a subband becomes slightly occupied [1]. Exchange and correlation give opposite contributions to the discontinuity, with correlation overcoming exchange. The associated jump in the intersubband energy is in excellent agreement with experimental data.

[1] S. Rigamonti and C. R. Proetto, Phys. Rev. Lett. 98, 066806 (2007).