Theory of excitonic states in lead salt quantum dots

Band-edge exciton states in bulk lead chalcogenides are 64-fold degenerate. In quantum dots (QDs), the degeneracy is lifted by the valley mixing and the electron-hole exchange interaction. To investigate their interplay we calculate excitonic states in PbS QDs within the tight-binding method. This allows one to trace the genesis of the bright excitonic states from the valley-degenerate states of the direct exciton which may be described within the effective mass model. We compute optical absorption spectra fully accounting for the exciton fine structure within the tight-binding method and extend the effective-mass model to include description of the inter-valley coupling.

[1]  F. Wise,et al.  Electronic structure and optical properties of PbS and PbSe quantum dots , 1997 .

[2]  P. Löwdin.  On the Non‐Orthogonality Problem Connected with the Use of Atomic Wave Functions in the Theory of Molecules and Crystals , 1950 .

[3]  Georg Kresse,et al.  Structural and electronic properties of lead chalcogenides from first principles , 2007 .

[4]  A. Zunger,et al.  The peculiar electronic structure of PbSe quantum dots. , 2006, Nano letters.

[5]  A. N. Babkina,et al.  The Role of Valley Anisotropy in Optical Absorption of Monodisperse PbS Nanocrystals , 2017 .

[6]  W. Tisdale,et al.  Monodisperse, air-stable PbS nanocrystals via precursor stoichiometry control. , 2014, ACS nano.

[7]  G. Czycholl,et al.  Tight-binding model for semiconductor quantum dots with a wurtzite crystal structure: From one-particle properties to Coulomb correlations and optical spectra , 2006 .

[8]  Kesheng Wu,et al.  Thick-Restart Lanczos Method for Large Symmetric Eigenvalue Problems , 2000, SIAM J. Matrix Anal. Appl..

[9]  H. Preier.  Recent advances in lead-chalcogenide diode lasers , 1979 .

[10]  D. Chadi.  Spin-orbit splitting in crystalline and compositionally disordered semiconductors , 1977 .

[11]  E. Sargent,et al.  Colloidal Quantum-Dot Photodetectors Exploiting Multiexciton Generation , 2009, Science.

[12]  Graf,et al.  Electromagnetic fields and dielectric response in empirical tight-binding theory. , 1995, Physical review. B, Condensed matter.

[13]  G. Koster,et al.  The Properties of the Thirty-Two Point Groups , 1963 .

[14]  I. Avdeev.  Shape effect on the valley splitting in lead selenide nanowires , 2019, Physical Review B.

[15]  Detlef-Matthias Smilgies,et al.  Kinetics of the self-assembly of nanocrystal superlattices measured by real-time in situ X-ray scattering. , 2016, Nature materials.

[16]  E. Sargent.  Infrared photovoltaics made by solution processing , 2009 .

[17]  Gregory D. Scholes,et al.  Colloidal PbS Nanocrystals with Size‐Tunable Near‐Infrared Emission: Observation of Post‐Synthesis Self‐Narrowing of the Particle Size Distribution , 2003 .

[18]  L. Kleinman,et al.  Energy Bands of PbTe, PbSe, and PbS , 1966 .

[19]  J. C. Slater,et al.  Simplified LCAO Method for the Periodic Potential Problem , 1954 .

[20]  Richard G Hennig,et al.  Predicting nanocrystal shape through consideration of surface-ligand interactions. , 2012, ACS nano.

[21]  J. Luther,et al.  Peak External Photocurrent Quantum Efficiency Exceeding 100% via MEG in a Quantum Dot Solar Cell , 2011, Science.

[22]  A. Malko,et al.  Intrinsic exciton photophysics of PbS quantum dots revealed by low-temperature single nanocrystal spectroscopy. , 2019, Nano letters.

[23]  M. Bawendi,et al.  Colloidal quantum--dot light-emitting diodes with metal-oxide charge transport layers , 2008 .

[24]  J. Jancu,et al.  Atomistic spin-orbit coupling and k∙p parameters in III-V semiconductors , 2005 .

[25]  Michael J. Frisch,et al.  Toward a systematic molecular orbital theory for excited states , 1992 .

[26]  M. Nestoklon,et al.  Anomalous Suppression of Valley Splittings in Lead Salt Nanocrystals , 2011, 1112.0056.

[27]  Fabio Beltram,et al.  Empirical spds^* tight-binding calculation for cubic semiconductors : general method and material parameters , 1998 .

[28]  P. Voisin,et al.  Giant spin splittings in GaSb/AlSb L-valley quantum wells , 2004 .

[29]  I. Moreels,et al.  Size-dependent optical properties of colloidal PbS quantum dots. , 2009, ACS nano.

[30]  Noah D Bronstein,et al.  Hydroxylation of the surface of PbS nanocrystals passivated with oleic acid , 2014, Science.

[31]  Niels Egede Christensen,et al.  Quasiparticle self-consistent GW calculations for PbS, PbSe, and PbTe: Band structure and pressure coefficients , 2010 .

[32]  M. Nestoklon,et al.  Valley and spin splittings in PbSe nanowires , 2017, 1705.08383.