Basic Energy Science (BES) Core Funding ‘Electronic Structure and Fundamental Physics of Semiconductor Nanostructures’. PI: Alex Zunger

This project uses atomistic pseudopotential theory including many-body configuration interacrion to understand spectroscopic effects in quantum nanostructures. A detailed summary to 2013-2016 period is here.

Key Words: Quantum dots, Wires, Quantum Materials, Topological Insulators, Inverse Design.

Project scope: The motivation and structure of this work is built on three observations:

(i) Testing our fundamental understanding of the basic many body interactions that govern the electronic properties of semiconductor nanostructures requires access to spectroscopically rich and highly resolved data. Alas, such high quality spectroscopy (numerous emission lines that are ~ 1 meV wide!) tends to exist mostly in rather large nanostructures (that have good structural perfection, nearly perfect passivation and isolation from the environment). Such are the self-assembled epitaxial systems (GaAs/AlAs[1]; InAs/GaAs [2];  recently Si [9-11]), containing typically 100,000 or 1,000,000 atoms per computational unit cell, or colloidal QD containing ~ 10,000 per cell [10-13]. This size regime is well outside the range of DFT methodologies. At the same time, continuum-like effective-mass methods (based on envelope functions) that can handle large nanostructures lack the atomistic resolution needed to describe the underlying electronic structure phenomenology. Our method is tailored at such structures. Using our previously developed screened- pseudopotential plus configuration interaction approach we can directly address million–atom nanostructures of the sort described above. Our scope is to use this methodology for understanding fundamental electronic processes in nano- and eventually mesoscopic systems.

(ii) Recent dramatic experimental advances now permit growth and spectroscopic characterization of different classes of nanostructures: Not just 0D dots [1]-[3], but also 2D films [4]-[6] and 1D nanowires [7]-[8]. These pose additional challenges to nanostructure theory: Can the same level of theory deal with 0D, 1D,and 2D?

(iii) Recent experimental advances have moved to nanostructures made of compounds that were previously not amenable to high-quality nano. This includes the recent advances in monolayer-thickness transition metal dichalcogenides [4]; HgTe ultra thin films and wells [5] and ‘droplet epitaxy’ [1] capable of growing self-assembled structures even if they lack strain (such as AlAs-GaAs QD).

The way large-scale calculations lead to theoretical discovery of new nanostructure mechanisms: Sometimes doing large scale (in our case, up to 2 million atoms) atomistic calculations helps uncover physical effects that alluded us otherwise (using small-dot model calculations). Examples include: (i) Discovery of a first-order, giant Rashba spin splitting in semiconductor nanowires [9] (ii) the discovery of a novel channel of light-hole to heavy-hole coupling in strained quantum dots, mediated by intermediate states (analogous to super exchange in magnetism) [3], (iii) prediction of emergent density of states features in nanowires [7] that are not associated with the conventional, orbitally classified states such a 1S, 1P, 1D. (iv) Microscopic explanation of the spectroscopic features observed in million-atom quantum dots embedded in nanowires [8]. (v) Careful calculation of the electronic states in HgTe/CdTe quantum wells at the critical well thickness where topological band inversion occur shows that the relevant HH1 and E1 states anti-cross rather than cross, leading to gapped Dirac cones. [5]


List of publications in which DOE- BES support to ER 46959-SC0010467, PI Alex Zunger at Colorado University is acknowledged [1]-[13]:“Electronic Structure and Fundamental Physics of Semiconductor Nanostructures.

A. Fundamental theory of electronic states and spectroscopy in Nano structures [1]- [3]:

[1] J. -W. Luo, G. Bester, A. Zunger,”Atomistic Pseudopotential Theory of Droplet Epitaxial GaAs/AlGaAs Quantum Dots , in: Z.M. Wang (Ed.), Nanodroplets,( BOOK) Springer New York, 2013: pp. 329–361. (April 21, 2015).

[2] B.P. Fingerhut, M. Richter, J.-W. Luo, A. Zunger, S. Mukamel,”2D optical photon echo spectroscopy of a self-assembled quantum dot”, Ann. Phys. 525 (2013) 31–42. doi:10.1002/andp.201200204.

[3] Jun-Wei Luo, Gabriel Bester, and Alex Zunger "Super coupling between heavy-hole and light-hole states in nanostructures" Phys. Rev B 92, 165301 (2015)

B.  2D Quantum wells and super lattice nanostructures [4]-[6]:

[4] L. Zhang, A. Zunger, “Evolution of Electronic Structure as a Function of Layer Thickness in Group-VIB Transition Metal Dichalcogenides: Emergence of Localization Prototypes”, Nano letters. 15 (2015) 949–957. Doi:10.1021/nl503717p.

[5] S.A. Tarasenko, M.V. Durnev, M.O. Nestoklon, E.L. Ivchenko, J.-W. Luo, A. Zunger, “Split Dirac cones in HgTe/CdTe quantum wells due to symmetry-enforced level anticrossing at interfaces”, Phys. Rev. B. Rapid Communication 91 (2015) 081302 doi:10.1103/PhysRevB.91.081302.

[6] J. Deng, A. Zunger, J.Z. Liu, “Cation ordering induced polarization enhancement for PbTiO3-SrTiO3 ferroelectric- dielectric superlattices”, Phys. Rev. B Rapid Communication B. 91 (2015) 081301. doi:10.1103/PhysRevB.91.081301

C.  1D nanowires [7]-[9]:                                                                                        

[7] J. Wang, J. -W. Luo, L. Zhang, A. Zunger, “Reinterpretation of the Expected Electronic Density of States of Semiconductor Nanowires”, Nano Letters. 15 (2015) 88–95. doi:10.1021 /nl5030062.

[8] M. Heiss, Y. Fontana, A. Gustafsson, G. Wüst, C. Magen, D.D. O’Regan, J.W. Luo, B. Ketterer, S. Conesa-Boj, A.V. Kuhlmann, J. Houel, E. Russo-Averchi, J.R. Morante, M. Cantoni, N. Marzari, J. Arbiol, A. Zunger, R.J. Warburton, A. Fontcuberta i Morral, “Self-assembled quantum dots in a nanowire system for quantum photonics”, Nature. Materials. 12 (2013) 439–444. Doi: 10.1038/nmat3557.

D. Silicon Nano crystals [10]-[13]:

[9]     L. Zhang, J. Luo, A. Saraiva, B. Koiller, A. Zunger, “Genetic design of enhanced valley splitting towards a spin qubit in silicon nanostructures”, Nature Communication 4 (2013) 2396. 

[10] I. Sychugov, F. Pevere, Jun-Wei Luo, Alex Zunger , Jan Linnros “Single-dot Absorption Spectroscopy and Theory of Silicon Nanocrystals “ Phy. Rev.B. Rapid Communication  93, 161413 (2016). 

[11] Benjamin G. Lee, Jun Wei Luo, Nathan R. Neale, Matthew C. Beard, Daniel Hiller Margit Zacharias, Alex Zunger, Pauls Stradins "Quasi-Direct Optical Transitions in Silicon Nano crystals exceeding the intensity of bulk transitions" Nano Letters 16, 1583-1589 (2016)

E. Design of structures with target properties [12]-[21]:

[12] Q. Liu, X. Zhang, L. B. Abdalla and A. Zunger, "Transforming common III-V and II-VI semiconductor compounds into two-dimensional topological heterostructures: The case of CdTe/InSb superlattices" Advaced Functiona Materials 26, 3259-3267 (2015)

[13] Jino Im, Giancarlo Trimarchi, Kenneth Poeppelmeier, and Alex Zunger "Incomplete Peierls-like chain dimerization as a mechanism for intrinsic conductivity and optical transparency: A La-Cu-O-S phase with mixed-anion layers as a case study" Phys. Rev B 92, 235139 (2015)

 [14] J.M. Rondinelli, K.R. Poeppelmeier, and A. Zunger "Towards Designed Functionalities in Oxide-based Electronic MaterialsApply.Phys.Letters.  Mater. 3, 080702 (2015)

[15] Xiuwen Zhang, Lijun Zhang, John D. Perkins, and Alex Zunger "Intrinsic transparent conductors without doping" Physical Review Letters. 115, 176602 (2015)

 [16] Giancarlo Trimarchi, Xiuwen Zhang, Michael Vermeer, Kenneth Poeppelmeier, Jacqueline Cantwell and Alex Zunger "Emergence of a few distinct structures from a single formal structure type during high-throughput screening for stable compounds: The case of RbCuS and RbCuSe" Phys. Rev B 92, 165103 (2015).

 [17] Michael J. Vermeer, Xiuwen Zhang, Giancarlo Trimarchi, Peter J. Chupas, Kenneth R. Poeppelmeier and Alex Zunger "Prediction and Synthesis of Strain Tolerant RbCuTe Crystals Based on Rotation of One-Dimensional Nano Ribbons within a Three-Dimensional Inorganic Network" J. Am. Chem. Soc. 137, 11383 (2015).

[18] F. Yan, X. Zhang, Yonggang Yu, L.Yu, A. Nagaraja, T.O. Mason, and Alex Zunger" Design and discovery of a novel Half‐Heusler transparent hole conductor made of all metallic heavy elements" Nature Communication 6, 7308 (2015).

[19] R. Gautier, X. Zhang, L. Hu, L. Yu, Y. Lin, T. O. L. Sunde, D. Chon, K. R. Poeppelmeier, A. Zunger,"Prediction and accelerated laboratory discovery of previously unknown 18-electron ABX compounds", Nature Chemistry 7, 308-316 (2015)

[20] G. Trimarchi, X. Zhang, A. J. Freeman, A. Zunger, "Structurally unstable AIIIBiO3 perovskites are predicted to be topological insulators but their stable structural forms are trivial band insulators," Phy. Rev. B. 90, 161111 (2014)

[21] L. Yu, A. Zunger,"A polarity-induced defect mechanism for conductivity and magnetism at polar-nonpolar oxide interfaces," Nature Communications 5, 5118 (2014).