Emergence of an excitonic collective mode in the dilute electron gas

Article

关键词: LOCAL-FIELD FACTOR;    METAL-INSULATOR-TRANSITION;    POTENTIAL EXPANSION METHOD;    SPIN-DENSITY WAVES;    DIELECTRIC FUNCTION;    2-DIMENSIONAL ELECTRON;    MOMENTUM DISTRIBUTION;    SUM-RULES;    NEGATIVE COMPRESSIBILITY;    CORRELATION ENERGIES;   

DOI  :  10.1103/PhysRevB.94.245106

来源: SCIE

【 摘 要 】

By comparing two expressions for the polarization function Pi (q, i omega) given in terms of two different local-field factors, G(+)(q, i omega) and G(s) (q, i omega), we have derived the kinetic-energy-fluctuation (or sixth-power) sum rule for the momentum distribution function n(p) in the three-dimensional electron gas. With use of this sum rule, together with the total-number (or second-power) and the kinetic-energy (or fourth-power) sum rules, we have obtained n(p) in the low-density electron gas at negative compressibility (namely, r(s) > 5.25 with r(s) being the conventional density parameter) up to r(s) approximate to 22 by improving on the interpolation scheme due to Gori-Giorge and Ziesche proposed in 2002. The obtained results for n(p) combined with the improved form for G(s) (q, omega + i0(+)) are employed to calculate the dynamical structure factor S(q, omega) to reveal that a giant peak, even bigger than the plasmon peak, originating from an excitonic collective mode made of electron-hole pair excitations, emerges in the low-omega region at vertical bar q vertical bar near 2pF (p(F): the Fermi wave number). Connected with this mode, we have discovered a singular point in the retarded dielectric function at omega = 0 and vertical bar q vertical bar approximate to 2p(F).

【 授权许可】

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