Creating emergent phenomena in oxide superlattices

ABSTRACT Complex oxides are record holder materials for many phenomena, including ferroelectricity, piezoelectricity, superconductivity and multiferroicity. Complex oxides often have

competing ground states with energies slightly higher than that of the true ground state. This competition is fortuitous because thermodynamic variables (for example, temperature, electric

field, magnetic field, stress and chemical potentials) can access these metastable phases that are usually hidden but emerge as the energetic landscape is reshaped by adjusting the

thermodynamic variables. Epitaxial superlattices are a platform for imposing thermodynamic boundary conditions to unleash the properties of hidden phases by altering the delicate balance

between competing spin, charge, orbital and lattice degrees of freedom. Additionally, a feature of complex oxides with large responses (large property coefficients) is the coexistence of

phases on the nanoscale. New phases can emerge at the heterointerfaces of oxide superlattices, and X-ray, electron, neutron and proximal probes as well as ab initio theoretical studies can

provide insights into these emergent phenomena. Access through your institution Buy or subscribe This is a preview of subscription content, access via your institution ACCESS OPTIONS Access

through your institution Access Nature and 54 other Nature Portfolio journals Get Nature+, our best-value online-access subscription $32.99 / 30 days cancel any time Learn more Subscribe to

this journal Receive 12 digital issues and online access to articles $119.00 per year only $9.92 per issue Learn more Buy this article * Purchase on SpringerLink * Instant access to full

article PDF Buy now Prices may be subject to local taxes which are calculated during checkout ADDITIONAL ACCESS OPTIONS: * Log in * Learn about institutional subscriptions * Read our FAQs *

Contact customer support SIMILAR CONTENT BEING VIEWED BY OTHERS THE EMERGENCE OF MAGNETIC ORDERING AT COMPLEX OXIDE INTERFACES TUNED BY DEFECTS Article Open access 20 July 2020 3D OXYGEN

VACANCY DISTRIBUTION AND DEFECT-PROPERTY RELATIONS IN AN OXIDE HETEROSTRUCTURE Article Open access 26 June 2024 METAL–FERROELECTRIC SUPERCRYSTALS WITH PERIODICALLY CURVED METALLIC LAYERS

Article 04 January 2021 REFERENCES * Schilling, A., Cantoni, M., Guo, J. D. & Ott, H. R. Superconductivity above 130 K in the Hg-Ba-Ca-Cu-O system. _Nature_ 363, 56–58 (1993). CAS 

Google Scholar  * Penney, T., Shafer, M. W. & Torrance, J. B. Insulator-metal transition and long-range magnetic order in EuO. _Phys. Rev. B_ 5, 3669–3674 (1972). Google Scholar  *

Anguelouch, A. et al. Properties of epitaxial chromium dioxide films grown by chemical vapor deposition using a liquid precursor. _J. Appl. Phys._ 91, 7140–7142 (2002). CAS  Google Scholar 

* Tomioka, Y., Asamitsu, A., Moritomo, Y. & Tokura, Y. Anomalous magnetotransport properties of Pr1-xCaxMnO3. _J. Phys. Soc. Jpn_ 64, 3626–3630 (1995). CAS  Google Scholar  * Li, J. et

al. Dramatically enhanced polarization in (001), (101), and (111) BiFeO3 thin films due to epitiaxial-induced transitions. _Appl. Phys. Lett._ 84, 5261–5263 (2004). CAS  Google Scholar  *

Vrejoiu, I. et al. Intrinsic ferroelectric properties of strained tetragonal PbZr0.2Ti0.8O3 obtained on layer–by–layer grown, defect–free single–crystalline films. _Adv. Mater._ 18,

1657–1661 (2006). CAS  Google Scholar  * Park, S.-E. & Shrout, T. R. Ultrahigh strain and piezoelectric behavior in relaxor based ferroelectric single crystals. _J. Appl. Phys._ 82,

1804–1811 (1997). CAS  Google Scholar  * Lee, J. H. et al. A strong ferroelectric ferromagnet created by means of spin–lattice coupling. _Nature_ 466, 954–958 (2010). CAS  Google Scholar  *

Cross, L. E. Relaxor ferroelectrics. _Ferroelectrics_ 76, 241–267 (1987). CAS  Google Scholar  * Jin, S. et al. Thousandfold change in resistivity in magnetoresistive La-Ca-Mn-O films.

_Science_ 264, 413–415 (1994). CAS  Google Scholar  * Dagotto, E. Complexity in strongly correlated electronic systems. _Science_ 309, 257–262 (2005). CAS  Google Scholar  * Bednorz, J. G.

& Müller, K. A. Possible high Tc superconductivity in the Ba-La-Cu-O system. _Z. Phys. B_ 64, 189–193 (1986). CAS  Google Scholar  * Bednorz, J. G., Takashige, M. & Müller, K. A.

Susceptibility measurements support high-Tc superconductivity in the Ba-La-Cu-O system. _Europhys. Lett._ 3, 379–386 (1987). CAS  Google Scholar  * Rudolph, P. (ed.) _Handbook of Crystal

Growth: Bulk Crystal Growth: Basic Techniques_ 2nd edn Vol. 2 (Elsevier, Amsterdam, 2015). * Heckmann, G. Die Gittertheorie der festen Körper. _Ergeb. Exakten Naturwiss._ 4, 100–153 (1925).

Google Scholar  * Nye, J. F. _Physical Properties of Crystals: Their Representation by Tensors and Matrices_ (Oxford Univ. Press, 1985). * Spaldin, N. A. & Fiebig, M. The renaissance of

magnetoelectric multiferroics. _Science_ 309, 391–392 (2005). CAS  Google Scholar  * Kalinin, S. V. & Spaldin, N. A. Functional ion defects in transition metal oxides. _Science_ 341,

858–859 (2013). CAS  Google Scholar  * Yi, D., Lu, N., Chen, X., Shen, S. & Yu, P. Engineering magnetism at functional oxides interfaces: manganites and beyond. _J. Phys. Condens.

Matter_ 29, 443004 (2017). Google Scholar  * Terashima, T. & Bando, Y. Formation of artificial superlattice composed of ultrathin layers of CoO and NiO by reactive evaporation. _J. Appl.

Phys._ 56, 3445–3447 (1984). CAS  Google Scholar  * Ramesh, R., Simion, B. & Thomas, G. Epitaxial magnetic garnet heterostructures. _J. Phys. IV_ 7, C1-695–C1-698 (1997). Google Scholar

  * Kawasaki, J. K. et al. Rutile IrO2/TiO2 superlattices: a hyperconnected analog to the Ruddelsden-Popper structure. _Phys. Rev. Mater._ 2, 054206 (2018). CAS  Google Scholar  * Haeni, J.

H. et al. Room-temperature ferroelectricity in strained SrTiO3. _Nature_ 430, 758–761 (2004). CAS  Google Scholar  * Choi, K. J. et al. Enhancement of ferroelectricity in strained BaTiO3

thin films. _Science_ 306, 1005–1009 (2004). CAS  Google Scholar  * Schlom, D. G. et al. Strain tuning of ferroelectric thin films. _Annu. Rev. Mater. Res._ 37, 589–626 (2007). CAS  Google

Scholar  * Warusawithana, M. P. et al. A ferroelectric oxide made directly on silicon. _Science_ 324, 367–370 (2009). CAS  Google Scholar  * Zeches, R. J. et al. A strain-driven morphotropic

phase boundary in BiFeO3. _Science_ 326, 977–980 (2009). CAS  Google Scholar  * He, Q. et al. Electrically controllable spontaneous magnetism in nanoscale mixed phase multiferroics. _Nat.

Commun._ 2, 225 (2011). CAS  Google Scholar  * Schlom, D. G. et al. Elastic strain engineering of ferroic oxides. _MRS Bull._ 39, 118–130 (2014). CAS  Google Scholar  * Iijima, K.,

Terashima, T., Bando, Y., Kamigaki, K. & Terauchi, H. Atomic layer growth of oxide thin films with perovskite-type structure by reactive evaporation. _J. Appl. Phys._ 72, 2840–2845

(1992). CAS  Google Scholar  * Bozovic, I. et al. Atomic-layer engineering of cuprate superconductors. _J. Supercond._ 7, 187–195 (1994). CAS  Google Scholar  * Specht, E. D., Christen, H.

M., Norton, D. P. & Boatner, L. A. X-ray diffraction measurement of the effect of layer thickness on the ferroelectric transition in epitaxial KTaO3/KNbO3 multilayers. _Phys. Rev. Lett._

80, 4317–4320 (1998). CAS  Google Scholar  * Schlom, D. G., Haeni, J. H., Lettieri, J. & Theis, C. D. Oxide nano-engineering using MBE. _Mater. Sci. Eng. B_ 87, 282–291 (2001). Google

Scholar  * Ohtomo, A., Muller, D. A., Grazul, J. L. & Hwang, H. Y. Artificial charge-modulation in atomic-scale perovskite titanate superlattices. _Nature_ 419, 378–380 (2002). CAS 

Google Scholar  * Warusawithana, M. P., Colla, E. V., Eckstein, J. N. & Weissman, M. B. Artificial dielectric superlattices with broken inversion symmetry. _Phys. Rev. Lett._ 90, 036802

(2003). Google Scholar  * Tenne, D. A. et al. Probing nanoscale ferroelectricity by ultraviolet Raman spectroscopy. _Science_ 313, 1614–1616 (2006). CAS  Google Scholar  * Bousquet, E. et

al. Improper ferroelectricity in perovskite oxide artificial superlattices. _Nature_ 452, 732–736 (2008). CAS  Google Scholar  * Ramesh, R. & Schlom, D. G. Whither oxide electronics.

_MRS Bull._ 33, 1006–1011 (2008). Google Scholar  * Zheng, H. et al. Multiferroic BaTiO3-CoFe2O4 nanostructures. _Science_ 303, 661–663 (2004). CAS  Google Scholar  * Mohaddes-Ardabili, L.

et al. Self-assembled single-crystal ferromagnetic iron nanowires formed by decomposition. _Nat. Mater._ 3, 533–538 (2004). CAS  Google Scholar  * Zheng, H. et al. Three-dimensional

heteroepitaxy in self-assembled BaTiO3-CoFe2O4 nanostructures. _Appl. Phys. Lett._ 85, 2035–2037 (2004). CAS  Google Scholar  * MacManus-Driscoll, J. L. et al. Strain control and spontaneous

phase ordering in vertical nanocomposite heteroepitaxial thin films. _Nat. Mater._ 7, 314–320 (2008). CAS  Google Scholar  * Machlin, E. S. & Chaudhari, P. (eds) _Synthesis and

Properties of Metastable Phases_ 11–29 (The Metallurgical Society, 1980). * Flynn, C. P. Strain-assisted epitaxial growth of new ordered compounds. _Phys. Rev. Lett._ 57, 599–602 (1986). CAS

  Google Scholar  * Bruinsma, R. & Zangwill, A. Structural transitions in epitaxial overlayers, _J. Phys._ 47, 2055–2073 (1986). CAS  Google Scholar  * Zunger, A. & Wood, D. M.

Structural phenomena in coherent epitaxial solids. _J. Cryst. Growth_ 98, 1–17 (1989). CAS  Google Scholar  * Kaul, A. R., Gorbenko, O. Y. & Kamenev, A. A. The role of heteroepitaxy in

the development of new thin-film oxide-based functional materials. _Russ. Chem. Rev._ 73, 861–880 (2007). Google Scholar  * Lee, C.-H. et al. Exploiting dimensionality and defect mitigation

to create tunable microwave dielectrics. _Nature_ 502, 532–536 (2013). CAS  Google Scholar  * Dingle, R., Stormer, H. L., Gossard, A. C. & Wiegmann, W. Electron mobilities in

modulation-doped semiconductor heterojunction superlattices. _Appl. Phys. Lett._ 33, 665–667 (1978). CAS  Google Scholar  * Tsukazaki, A. et al. Quantum Hall effect in polar oxide

heterostructures. _Science_ 315, 1388–1391 (2007). CAS  Google Scholar  * Tsukazaki, A. et al. Observation of the fractional quantum Hall effect in an oxide. _Nat. Mater._ 9, 889–893 (2010).

CAS  Google Scholar  * Harrison, W. A., Kraut, E. A., Waldrop, J. R. & Grant, R. W. Polar heterojunction interfaces. _Phys. Rev. B_ 18, 4402–4410 (1978). CAS  Google Scholar  * Tasker,

P. W. The stability of ionic crystal surfaces. _J. Phys. C_ 12, 4977–4984 (1979). CAS  Google Scholar  * Ohtomo, A. & Hwang, H. Y. A high-mobility electron gas at the LaAlO3/SrTiO3

heterointerface. _Nature_ 427, 423–426 (2004). CAS  Google Scholar  * Nakagawa, N., Hwang, H. Y. & Muller, D. A. Why some interfaces cannot be sharp. _Nat. Mater._ 5, 204–209 (2006). CAS

  Google Scholar  * Schlom, D. G. & Mannhart, J. Interface takes charge over Si. _Nat. Mater._ 10, 168–169 (2011). CAS  Google Scholar  * Mundy, J. A. et al. Atomically engineered

ferroic layers yield a room-temperature magnetoelectric multiferroic. _Nature_ 537, 523–527 (2016). CAS  Google Scholar  * Freund, L. B. & Suresh, S. in _Thin Film Materials: Stress,

Defect Formation and Surface Evolution_ 60–83; 283–290; 396–416 (Cambridge Univ. Press, 2003). * Klenov, D. O., Donner, W., Foran, B. & Stemmer, S. Impact of stress on oxygen vacancy

ordering in epitaxial La0.5Sr0.5CoO3−∂ thin films on (001) LaAlO3. _Appl. Phys. Lett._ 82, 3427 (2003). CAS  Google Scholar  * Donner, W. et al. Epitaxial strain-induced chemical ordering in

La0.5Sr0.5CoO3−δ films on SrTiO3. _Chem. Mater._ 23, 984–988 (2011). CAS  Google Scholar  * Boullay, P. et al. Structure determination of a brownmillerite Ca2Co2O5 thin film by precession

electron diffraction. _Phys. Rev. B_ 79, 184108 (2009). Google Scholar  * Nguyen, L. D., Brown, A. S., Thompson, M. A. & Jelloian, L. M. 50-nm self-aligned-gate pseudomorphic

AlInAs/GaInAs high electron mobility transistors. _IEEE Trans. Electron Devices_ 39, 2007–2014 (1992). CAS  Google Scholar  * Welser, J., Hoyt, J. L. & Gibbons, J. F. Electron mobility

enhancement in strained-Si n-type metal-oxide-semiconductor field-effect transistors. _IEEE Electron Device Lett._ 15, 100–102 (1994). CAS  Google Scholar  * Newnham, R. E., Skinner, D. P.

& Cross, L. E. Connectivity and piezoelectric-pyroelectric composites. _Mater. Res. Bull._ 13, 525–536 (1978). CAS  Google Scholar  * Huang, J., MacManus-Driscoll, J. L. & Wang, H.

New epitaxy paradigm in epitaxial self-assembled oxide vertically aligned nanocomposite thin films. _J. Mater. Res._ 32, 4054–4066 (2017). CAS  Google Scholar  * Hamasaki, Y. et al. Crystal

isomers of ScFeO3. _Cryst. Growth Des._ 16, 5214–5222 (2016). CAS  Google Scholar  * Lee, S., Ivanov, I. N., Keum, J. K. & Lee, H. N. Epitaxial stabilization and phase instability of VO2

polymorphs. _Sci. Rep._ 6, 19621 (2016). CAS  Google Scholar  * Cava, R. J. Structural chemistry and the local charge picture of copper oxide superconductors. _Science_ 247, 656–662 (1990).

CAS  Google Scholar  * Sai, N., Meyer, B. & Vanderbilt, D. Compositional inversion symmetry breaking in ferroelectric perovskites. _Phys. Rev. Lett._ 84, 5636–5639 (2000). CAS  Google

Scholar  * Ederer, C. & Spaldin, N. A. Magnetoelectrics: a new route to magnetic ferroelectrics. _Nat. Mater._ 3, 849–851 (2004). CAS  Google Scholar  * Kawamura, K. et al. Structural

origin of the anisotropic and isotropic thermal expansion of K2NiF4-type LaSrAlO4 and Sr2TiO4. _Inorg. Chem._ 54, 3896–3904 (2015). CAS  Google Scholar  * Birol, T., Benedek, N. A. &

Fennie, C. J. Interface control of emergent ferroic order in Ruddlesden-Popper Srn+1TinO3n+1. _Phys. Rev. Lett._ 107, 517–519 (2011). Google Scholar  * Junquera, J., Zimmer, M., Ordejón, P.

& Ghosez, P. First-principles calculation of the band offset at BaO/BaTiO3 and SrO/SrTiO3 interfaces. _Phys. Rev. B_ 67, 155327 (2003). Google Scholar  * Bousquet, E., Junquera, J. &

Ghosez, P. First-principles study of competing ferroelectric and antiferroelectric instabilities in BaTiO3/BaO superlattices. _Phys. Rev. B_ 82, 045426 (2010). Google Scholar  *

Verissimo-Alves, M., García-Fernández, P., Bilc, D. I., Ghosez, P. & Junquera, J. Highly confined spin-polarized two-dimensional electron gas in SrTiO3/SrRuO3 Superlattices. _Phys. Rev.

Lett._ 108, 107003 (2012). Google Scholar  * Wojdeł, J. C. & Íñiguez, J. Ferroelectric transitions at ferroelectric domain walls found from first-principles. _Phys. Rev. Lett._ 112,

247603 (2014). Google Scholar  * Wang, J. et al. Epitaxial BiFeO3 multiferroic thin film heterostructures. _Science_ 299, 1719–1722 (2003). CAS  Google Scholar  * Belik, A. A. et al. Neutron

powder diffraction study on the crystal and magnetic structures of BiCoO3. _Chem. Mater._ 18, 798–803 (2006). CAS  Google Scholar  * Li, M.-R. et al. A polar corundum oxide displaying weak

ferromagnetism at room temperature. _J. Am. Chem. Soc._ 134, 3737–3747 (2012). CAS  Google Scholar  * Pitcher, M. J. et al. Tilt engineering of spontaneous polarization and magnetization

above 300 K in a bulk layered perovskite. _Science_ 347, 420–424 (2015). CAS  Google Scholar  * Bossak, A. A. et al. XRD and HREM studies of epitaxially stabilized hexagonal orthoferrites

RFeO3 (R = Eu−Lu). _Chem. Mater._ 16, 1751–1755 (2004). CAS  Google Scholar  * Dawber, M. et al. Unusual behavior of the ferroelectric polarization in PbTiO3/SrTiO3 superlattices. _Phys.

Rev. Lett._ 95, 177601 (2005). CAS  Google Scholar  * Kwestroo, W. & Paping, H. A. M. The systems BaO-SrO-TiO2, BaO-CaO-TiO2, and SrO-CaO-TiO2. _J. Am. Ceram. Soc._ 42, 292–299 (1959).

CAS  Google Scholar  * Mundy, J. A. et al. A high-energy density antiferroelectric made by interfacial electrostatic engineering. Preprint at _arXiv_ https://arxiv.org/abs/1812.09615 (2018).

* Jiang, J. C., Pan, X. Q., Tian, W., Theis, C. D. & Schlom, D. G. Abrupt PbTiO3/SrTiO3 superlattices grown by reactive molecular beam epitaxy. _Appl. Phys. Lett._ 74, 2851–2853 (1999).

CAS  Google Scholar  * Naumov, I. I., Bellaiche, L. & Fu, H. Unusual phase transitions in ferroelectric nanodisks and nanorods. _Nature_ 432, 737–740 (2004). CAS  Google Scholar  *

Prosandeev, S. & Bellaiche, L. Characteristics and signatures of dipole vortices in ferroelectric nanodots: first-principles-based simulations and analytical expressions. _Phys. Rev. B_

75, 094102 (2007). Google Scholar  * Yadav, A. K. et al. Observation of polar vortices in oxide superlattices. _Nature_ 530, 198–201 (2016). CAS  Google Scholar  * Dawber, M. & Bousquet,

E. New developments in artificially layered ferroelectric oxide superlattices. _MRS Bull._ 38, 1048–1055 (2013). CAS  Google Scholar  * Benedek, N. & Fennie, C. Hybrid improper

ferroelectricity: A mechanism for controllable polarization-magnetization coupling. _Phys. Rev. Lett._ 106, 107204 (2011). Google Scholar  * Oh, Y. S., Luo, X., Huang, F.-T., Wang, Y. &

Cheong, S.-W. Experimental demonstration of hybrid improper ferroelectricity and the presence of abundant charged walls in (Ca Sr)3Ti2O7 crystals. _Nat. Mater._ 14, 407–413 (2015). CAS 

Google Scholar  * Ravichandran, J. et al. Crossover from incoherent to coherent phonon scattering in epitaxial oxide superlattices. _Nat. Mater._ 13, 168–172 (2014). CAS  Google Scholar  *

Simkin, M. & Mahan, G. Minimum thermal conductivity of superlattices. _Phys. Rev. Lett._ 84, 927–930 (2000). CAS  Google Scholar  * Shafer, P. et al. Emergent chirality in the electric

polarization texture of titanate superlattices. _Proc. Natl Acad. Sci. USA_ 115, 915–920 (2018). CAS  Google Scholar  * Lagerwall, S. T. & Dahl, I. Ferroelectric liquid crystals. _Mol.

Cryst. Liq. Cryst._ 114, 151–187 (1984). CAS  Google Scholar  * Damodaran, A. R. et al. Phase coexistence and electric-field control of toroidal order in oxide superlattices. _Nat. Mater._

16, 1003–1009 (2017). CAS  Google Scholar  * Zubko, P. et al. Negative capacitance in multidomain ferroelectric superlattices. _Nature_ 534, 524–528 (2016). CAS  Google Scholar  *

Salahuddin, S. & Datta, S. Use of negative capacitance to provide voltage amplification for low power nanoscale devices. _Nano Lett._ 8, 405–410 (2008). CAS  Google Scholar  * Khan, A.

I. et al. Negative capacitance in a ferroelectric capacitor. _Nat. Mater._ 14, 182–186 (2015). CAS  Google Scholar  * Yadav, A. K. et al. Spatially resolved steady-state negative

capacitance. _Nature_ 8, 405 (2019). Google Scholar  * Salahuddin, S., Ni, K. & Datta, S. The era of hyper-scaling in electronics. _Nat. Electron._ 1, 442–450 (2018). Google Scholar  *

Kwon, D. et al. Response speed of negative capacitance FinFETs. Presented at the 2018 IEEE Symposium on VLSI Technology, Honolulu, HI (2018). * Shibuya, K., Kawasaki, M. & Tokura, Y.

Metal-insulator transitions in TiO2/VO2 superlattices. _Phys. Rev. B_ 82, 205118 (2010). Google Scholar  * Gibert, M., Zubko, P., Scherwitzl, R., Íñiguez, J. & Triscone, J.-M. Exchange

bias in LaNiO3-LaMnO3 superlattices. _Nat. Mater._ 11, 195–198 (2012). CAS  Google Scholar  * Hirai, D., Matsuno, J. & Takagi, H. Fabrication of (111)-oriented Ca0.5Sr0.5IrO3/SrTiO3

superlattices—A designed playground for honeycomb physics. _APL Mater._ 3, 041508 (2015). Google Scholar  * Kim, T. H. et al. Polar metals by geometric design. _Nature_ 533, 68–72 (2016).

CAS  Google Scholar  * Choi, W. S. et al. Strain-induced spin states in atomically ordered cobaltites. _Nano Lett._ 12, 4966–4970 (2012). CAS  Google Scholar  * Rondinelli, J. M. &

Spaldin, N. A. Structure and properties of functional oxide thin films: insights from electronic-structure calculations. _Adv. Mater._ 23, 3363–3381 (2011). CAS  Google Scholar  *

Rondinelli, J. M., May, S. J. & Freeland, J. W. Control of octahedral connectivity in perovskite oxide heterostructures: An emerging route to multifunctional materials discovery. _MRS

Bull._ 37, 261–270 (2012). CAS  Google Scholar  * Ohnishi, T., Shibuya, K., Yamamoto, T. & Lippmaa, M. Defects and transport in complex oxide thin films. _J. Appl. Phys._ 103, 103703

(2008). Google Scholar  * Smith, E. H. et al. Exploiting kinetics and thermodynamics to grow phase-pure complex oxides by molecular-beam epitaxy under continuous codeposition. _Phys. Rev.

Mater._ 1, 023403 (2017). Google Scholar  * Günther, K. G. Aufdampfschichten aus halbleitenden III — V-Verbindungen. _Z. Naturforsch. A_ 13, 1081–1089 (1958). Google Scholar  * Freller, H.

& Günther, K. G. Three-temperature method as an origin of molecular beam epitaxy. _Thin Solid Films_ 88, 291–307 (1982). CAS  Google Scholar  * Holman, R. L. & Fulrath, R. M.

Intrinsic nonstoichiometry in the lead zirconate-lead titanate system determined by Knudsen effusion. _J. Appl. Phys._ 44, 5227–5236 (1973). CAS  Google Scholar  * Eisa, M. A., Abadir, M. F.

& Gadalla, A. M. The system TiO2-Pb-O in air. _Trans. J. Br. Ceram. Soc._ 79, 100–104 (1980). CAS  Google Scholar  * Hurle, D. T. J. A thermodynamic analysis of native point defect and

dopant solubilities in zinc-blende III–V semiconductors. _J. Appl. Phys._ 107, 121301 (2010). Google Scholar  * Sai, N., Rabe, K. M. & Vanderbilt, D. Theory of structural response to

macroscopic electric fields in ferroelectric systems. _Phys. Rev. B_ 66, 104108 (2002). Google Scholar  * Zhou, Y. & Rabe, K. M. Determination of ground-state and low-energy structures

of perovskite superlattices from first principles. _Phys. Rev. B_ 89, 214108 (2014). Google Scholar  * Wojdeł, J. C., Hermet, P., Ljungberg, M. P., Ghosez, P. & Íñiguez, J.

First-principles model potentials for lattice-dynamical studies: general methodology and example of application to ferroic perovskite oxides. _J. Phys. Condens. Matter_ 25, 305401 (2013).

Google Scholar  * García-Fernández, P., Wojdeł, J. C., Íñiguez, J. & Junquera, J. Second-principles method for materials simulations including electron and lattice degrees of freedom.

_Phys. Rev. B_ 93, 195137 (2016). Google Scholar  * Rabe, K. M. & Joannopoulos, J. D. Ab initio determination of a structural phase transition temperature. _Phys. Rev. Lett._ 59, 570–573

(1987). CAS  Google Scholar  * Chen, L.-Q. Phase-field method of phase transitions/domain structures in ferroelectric thin films: A review. _J. Am. Ceram. Soc._ 91, 1835–1844 (2008). CAS 

Google Scholar  * Hong, Z. et al. Stability of polar vortex lattice in ferroelectric superlattices. _Nano Lett._ 17, 2246–2252 (2017). CAS  Google Scholar  * Ohashi, S. et al. Compact laser

molecular beam epitaxy system using laser heating of substrate for oxide film growth. _Rev. Sci. Instrum._ 70, 178–183 (1999). CAS  Google Scholar  * Jäger, M., Teker, A., Mannhart, J. &

Braun, W. Independence of surface morphology and reconstruction during the thermal preparation of perovskite oxide surfaces. _Appl. Phys. Lett._ 112, 111601 (2018). Google Scholar  * King,

P. D. C. et al. Atomic-scale control of competing electronic phases in ultrathin LaNiO3. _Nat. Nanotechnol._ 9, 443–447 (2014). CAS  Google Scholar  * Tsui, D. C., Stormer, H. L. &

Gossard, A. C. Two-dimensional magnetotransport in the extreme quantum limit. _Phys. Rev. Lett._ 48, 1559–1562 (1982). CAS  Google Scholar  * Hwang, H. Y. et al. Emergent phenomena at oxide

interfaces. _Nat. Mater._ 11, 103–113 (2012). CAS  Google Scholar  * Manipatruni, S., Nikonov, D. E. & Young, I. A. Beyond CMOS computing with spin and polarization. _Nat. Phys._ 14,

338–343 (2018). CAS  Google Scholar  * Manipatruni, S. et al. Scalable energy-efficient magnetoelectric spin–orbit logic. _Nature_ 565, 35–42 (2018). Google Scholar  Download references

ACKNOWLEDGEMENTS For more than two decades, the authors have been extremely fortunate to have the pleasure to collaborate with outstanding colleagues within their home institutions and

around the world. The authors are grateful to their past and current students and postdocs, who have made their learning experience much richer. The authors are also fortunate to have been

funded from a variety of sources, enabling complementary aspects of their research activity, particularly the US National Science Foundation (NSF)-Materials Research Science and Engineering

Centers (MRSEC), US Department of Energy, US Army Research Office (ARO)-Multidisciplinary University Research Initiative (MURI), US Office of Naval Research (ONR)-MURI, Semiconductor

Research Corporation-Western Institute of Nanoelectronics (SRC-WIN), Nanoelectronics Research Initiative (NRI), Joint University Microelectronics Program (JUMP) and the NSF-Natural Sciences

and Engineering Research Council of Canada (NSERC). The two examples discussed in detail in this Review were primarily supported by the US Department of Energy, Office of Basic Sciences,

Division of Materials Sciences and Engineering, under award no. DE-SC0002334 (for the work at Cornell University) and by the ARO under grant W911NF-16-1-0315 and the Gordon and Betty Moore

Foundation’s EPiQS Initiative (for the work at University of California, Berkeley). AUTHOR INFORMATION AUTHORS AND AFFILIATIONS * Department of Materials Science & Engineering and

Department of Physics, University of California, Berkeley, CA, USA Ramamoorthy Ramesh * Department of Materials Science and Engineering and Kavli Institute at Cornell for Nanoscale Science,

Cornell University, Ithaca, NY, USA Darrell G. Schlom Authors * Ramamoorthy Ramesh View author publications You can also search for this author inPubMed Google Scholar * Darrell G. Schlom

View author publications You can also search for this author inPubMed Google Scholar CONTRIBUTIONS This Review was conceived, discussed and written by R.R. and D.G.S. CORRESPONDING AUTHORS

Correspondence to Ramamoorthy Ramesh or Darrell G. Schlom. ETHICS DECLARATIONS COMPETING INTERESTS The authors declare no competing interests. ADDITIONAL INFORMATION PUBLISHER’S NOTE

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. RIGHTS AND PERMISSIONS Reprints and permissions ABOUT THIS ARTICLE CITE

THIS ARTICLE Ramesh, R., Schlom, D.G. Creating emergent phenomena in oxide superlattices. _Nat Rev Mater_ 4, 257–268 (2019). https://doi.org/10.1038/s41578-019-0095-2 Download citation *

Published: 19 March 2019 * Issue Date: April 2019 * DOI: https://doi.org/10.1038/s41578-019-0095-2 SHARE THIS ARTICLE Anyone you share the following link with will be able to read this

content: Get shareable link Sorry, a shareable link is not currently available for this article. Copy to clipboard Provided by the Springer Nature SharedIt content-sharing initiative