Spin Phenomena in Quantum Dots and Optics of Novel Nano-Structured Materials

Researchers

Academic Staff:	Alexander Tartakovskii
Post-Docs:	Evgeny Chekhovich
PhD Students:	Daniel Sercombe Romain Toro Osvaldo Del Pozo Zamudio Stefan Schwarz Andreas Waeber

Overview of Research Projects

1. Spin in Nanometer-Scale Semiconductors

Fast manipulation of nuclear spins in a quantum dots using rf pulses

Electron and hole spins in solid-state nano-structures possess unique properties with favourably long spin coherence, and with high potential for fast coherent optical, magnetic and electrical control. The major challenge we undertake in our studies on this subject is the realisation of spin-qubits based on single spins with coherence in the ms range, and the development of optical and microwave control strategies enabling fast hole and electron spin operations in single quantum dots (QDs). In III-V semiconductor nano-structures the dominant mechanism of spin information leakage to the environment (decoherence) is magnetic interaction with slowly fluctuating nuclear spins of the lattice. In our experiments we have learned a great deal about nuclear spins, and have developed new nano-NMR techniques for control of tiny ensembles of nuclear spins in semiconductor QDs. These studies have opened new possibilities for non-invasive structural studies using nano-NMR, and in future will allow exploration of unusual collective behavior of nuclear spins in nano-structures.

2. Atomically Thin 2D Materials

AFM of a MoS2 flake deposited on a rough (PECVD grown) SiO2 substrate. AFM by B Robinson and O Kolosov (Lancaster).

Recent success in fabrication of ultrathin layered materials such as graphene has opened up a way to explore new low-dimensional physics. Here we focus on atomically thin materials which can emit light in the near infra-red and visible spectrum. Current activities are centered around MoS2, a transition metal chalcogenide material, composed of covalently bonded S-Mo-S sheets held together by weak van der Waals forces. In its bulk form, MoS2 is believed to be an indirect semiconductor, and does not exhibit bright emission. However, when thinned down to a few atomic monolayers, MoS2 emits light up to room temperature. It is a robust material, withstanding relatively high temperatures, which enables fabrication of new types of optical devices, one of the goals of our work. The family of layered materials is very large and includes semiconductors, metals and superconductors. In our group we have recently formed collaborations with suppliers of many types of such materials, and are rapidly increasing our effort in this research area.

3. III-V semiconductors grown on Si

TEM shows GaAs grown on Si and dislocations captured by quantum well strain filters. TEM by R Beanland and A Sanchez (Warwick); sample grown by HY Liu (UCL).

This is a new area of research for us, where nonetheless we have achieved first important results using III-V nanowires grown directly on unpatterned Si substrates and InGaAs/GaAs quantum dots placed in photonic crystal nano-cavities fabricated in GaAs grown straight on Si. Here our group enjoys very fruitful collaboration with Prof Huiyun Liu, who is the founder of the MBE crystal growth facility at UCL. Incorporating photonic components onto a Si platform has been a powerful driver behind the development of Si photonics for the last twenty years, with a key motivation being the development of on-chip and chip-chip optical interconnects . As a result of this, Si photonics has become a mature field of research and technology in its own right. However, the indirect band-gap of Si has severely restricted the development of light sources integrated directly with Si components. III-V semiconductor materials provide a mature technology with light emitting devices, but the direct growth on Si is difficult because of lattice mismatch. Integrating quantum light sources with Si can realise new functionality as well as reducing the production costs of quantum dot quantum light sources for commercial applications such as Quantum Key Distribution. Another recent development is the use of nanowires for solar cells, where growth on Si is a very attractive option.

Opportunities in our group

Experimental set-up for measurements of the nuclear spin dynamics in individual quantum dots. The picture shows optics assembled above the optical port of the AttoCube magneto-cryostat system.

The group possesses state of the art experimental equipment to study nano-structured materials at low temperatures down to 4 Kelvin and high magnetic fields up to 10 Tesla. The type of experiments we work on can be best described as optical magneto-microscopy at low temperatures. Experiments are carried out in our two laboratories (see photos). Our equipment base is constantly growing. Recent examples are a new vector magnet (to be installed in March 2013) enabling arbitrary rotation of magnetic field up to 4.5 Tesla in a plane, and micro-wave signal generator (up to 40 GHz) and spectrum analyzer.

In addition to laboratory work, all personnel in our group are trained to use modern clean room facilities at the III-V National Centre. There they learn and then use electron-beam and optical lithography, deposition of thin metal and dielectric films, various etching and microscopy techniques.

All researchers including PhD students regularly attend international and national conferences that are held all around the world in places such as Korea (QD2008, ICPS2010), Brazil (ICPS2008), Florida (MSS2011), or closer to home in France (Paris, OECS2011), Switzerland (Zurich, ICPS2012).

New spectroscopy system installed in 2012 with the latest model of Princeton Instruments CCD.

40 GHz Signal Generator, just arrived and ready to be used in new electron spin resonance experiments

The team

A well-balanced team of PhD students, post-doctoral and visiting researchers and more senior staff. We are closely linked with other quantum dot and photonics activities in the larger group led by Prof M Skolnick.

Andreas Waeber aligning micro-PL set-up in one of the labs.

Evgeny Chekhovich is launching new nano-NMR measurements in semiconductor quantum dots.

Collaborations

We have established a wide range of collaborations with research and industrial groups in the UK and overseas. Our industrial collaborations/contacts include: Dr Mark Stevenson and Dr Andrew Shields, Toshiba Research Europe (Cambridge). Dr Aleksey Andreev, Hitachi Cambridge Laboratory; Prof Khaled Karrai, Attocube Systems AG (Germany).

We are also closely linked with many academic groups in Europe: Dr Kirill Kavokin and Dr Mikhail Glazov, Ioffe Institute St Petersburg (Russia). Dr Richard Beanland and Dr Ana Sanchez, Warwick University; Prof Huiyun Liu, UCL; Dr Pascale Senellart and Dr Aristide Lemaitre, LPN-CNRS (Marcoussis, France). Prof Vladimir Falko and Dr Oleg Kolosov, Lancaster University; Prof Dmitri Yakovlev and Dr Ilya Akimov, TU Dortmund (Germany). Prof Guido Burkard, University of Konstanz (Germany). Dr Ceyhun Bulutay, Bilkent University (Ankara, Turkey). Dr Nikolai Kolesnikov, Institute of Solid State Physics (Chernogolovka, Russia).

Alumni

Former postdocs:
Dr Maxim Makhonin - Postdoctoral fellow in Sheffield
Dr Odilon Couto - Lecturer at Universidade Estadual de Campinas - Instituto de Fisica "Gleb Wataghin", Brazil

Former PhD students:
Dr Joanna Skiba-Szymanska - Research Scientist at Toshiba Research Europe Limited
Dr Claire Elliott - Research Scientist at National Physical Laboratory
Dr Nasser Babazadeh - Postdoctoral researcher at University of Sheffield
Jorge Puebla - Research engineer at Attocube Systems AG (Munich, Germany)

Publicity

"Scientists view the atomic structure of the crystal under the optical microscope", press-release by University of Sheffield, December 2012, link
"Quantum dots: Reading the signs", Bernhard Urbaszek, News and Views, Nature Physics, doi:10.1038/nphys2537, December 2012
"Quantum dots: Strain is a problem no more", Daniel Gammon, News and Views, Nature Nanotechnology 7,621, doi:10.1038/nnano.2012.171, October 2012
"New wave of technologies possible after ground-breaking analysis tool developed", press-release by University of Sheffield, August 2012, link
"Quantum information: Noisy neighbours under control", Guido Burkard, News and Views, Nature Materials 10, 811, doi:10.1038/nmat3154, October 2011
"New research offers breakthrough in nanotechnology", press-release by University of Sheffield, August 2011, link
"Flip-flops in the dots", Research Highlights, Nature Materials 6, 87 (2007), doi:10.1038/nmat1838

Recent Publications (from 2007)

Books

"Quantum Dots: Optics, Electron Transport and Future Applications" edited by A. Tartakovskii, Cambridge University Press (2012)

Book Chapters

A. I. Tartakovskii, "Spin phenomena in self-assembled quantum dots" in "Self-Assembled Quantum Dots", Springer, (2008).
A. I. Tartakovskii, A. Russell, V. I. Fal'ko, M. S. Skolnick, "Nuclear spin switch in semiconductor quantum dots" in "Semiconductor Quantum Bits", World Scientific Publishing Co. (2008).

Papers

Restoring mode degeneracy in H1 photonic crystal cavities by uniaxial strain tuning
I. J. Luxmoore, E. Daghigh Ahmadi, B. J. Luxmoore, N. A. Wasley, A. I. Tartakovskii, M. Hugues, M. S. Skolnick, and A. M. Fox
Applied Physics Letters 100 121116 (2012)
Structural analysis of strained quantum dots using nuclear magnetic resonance
E.A. Chekhovich, K.V. Kavokin, J. Puebla, A.B. Krysa, M. Hopkinson, A.D. Andreev, A.M. Sanchez, R. Beanland, M.S. Skolnick, A.I. Tartakovskii
Nature Nanotechnology 7 646-650 (2012) http://www.nature.com/nnano/journal/v7/n10/full/nnano.2012.142.html
Effect of a GaAsP shell on the optical properties of self-catalyzed GaAs nanowires grown on silicon
O. D. D. Couto, D. Sercombe, J. Puebla, L. Otubo, I. J. Luxmoore, M. Sich, T. J. Elliott, E. A. Chekhovich, L. R. Wilson, M. S. Skolnick, H. Y. Liu, A. I. Tartakovskii
Nano Letters 12 10 5269–5274 (2012) http://pubs.acs.org/doi/abs/10.1021/nl302490y
Element-sensitive measurement of the hole–nuclear spin interaction in quantum dots
E. A. Chekhovich, M. M. Glazov, A. B. Krysa, M. Hopkinson, P. Senellart, A. Lemaître, M. S. Skolnick, A. I. Tartakovskii
Nature Physics AOP - (2012) http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys2514.html
Laser Location and Manipulation of a Single Quantum Tunneling Channel in an InAs Quantum Dot
O. Makarovsky, E. E. Vdovin, A. Patane, L. Eaves, M. N. Makhonin, A. I. Tartakovskii, M. Hopkinson
Physical Review Letters 108 11 117402 (2012) http://dx.doi.org/10.1103/PhysRevLett.108.117402
Fast control of nuclear spin polarization in an optically pumped single quantum dot
M. N. Makhonin, K. V. Kavokin, P. Senellart, A. Lemaître, A. J. Ramsay, M. S. Skolnick, A. I. Tartakovskii
Nature Materials 10 844-848 (2011) http://www.nature.com/nmat/journal/v10/n11/full/nmat3102.html
Quantum information: Holes avoid decoherence
A.I. Tartakovskii
Nature Photonics 5 647-649 (2011) dx.doi.org/10.1038/nphoton.2011.262
Light-polarization-independent nuclear spin alignment in a quantum dot
E. A. Chekhovich, A. B. Krysa, M. S. Skolnick, A. I. Tartakovskii
Physical Review B 83 125318 (2011) http://link.aps.org/doi/10.1103/PhysRevB.83.125318
Charge control in InP/(Ga,In)P single quantum dots embedded in Schottky diodes
O. D. D. Couto Jr., J. Puebla, E. A. Chekhovich, I. J. Luxmoore, C. J. Elliott, N. Babazadeh, M. S. Skolnick, A. I. Tartakovskii
Physical Review B 84 125301 (2011) http://prb.aps.org/abstract/PRB/v84/i12/e125301
Direct Measurement of the Hole-Nuclear Spin Interaction in Single InP/GaInP Quantum Dots Using Photoluminescence Spectroscopy
E. A. Chekhovich, A. B. Krysa, M. S. Skolnick, and A. I. Tartakovskii
Physical Review Letters 106 027402 (2011) http://prl.aps.org/abstract/PRL/v106/i2/e027402
Control of spontaneous emission from InP single quantum dots in GaInP photonic crystal nanocavities
I. J. Luxmoore, E. Daghigh Ahmadi, N. A. Wasley, A. M. Fox, A. I. Tartakovskii, A. B. Krysa, and M. S. Skolnick
Applied Physics Letters 97 18 181104 (2010) http://link.aip.org/link/?APL/97/181104
Dynamics of optically induced nuclear spin polarization in individual InP/GaInP quantum dots
E. A. Chekhovich, M. N. Makhonin, J. Skiba-Szymanska, A. B. Krysa, V. D. Kulakovskii, M. S. Skolnick, A. I. Tartakovskii
Physical Review B 81 245308 (2010) http://link.aps.org/doi/10.1103/PhysRevB.81.245308
Optically tunable nuclear magnetic resonance in a single quantum dot
M. N. Makhonin, E. A. Chekhovich, P. Senellart, A. Lemaître, M. S. Skolnick, A. I. Tartakovskii
Physical Review B 82 161309(R) (2010) http://link.aps.org/doi/10.1103/PhysRevB.82.161309
Pumping of Nuclear Spins by Optical Excitation of Spin-Forbidden Transitions in a Quantum Dot
E. A. Chekhovich, M. N. Makhonin, K. V. Kavokin, A. B. Krysa, M. S. Skolnick, A. I. Tartakovskii
Physical Review Letters 104 066804 (2010) http://link.aps.org/doi/10.1103/PhysRevLett.104.066804
Suppression of nuclear spin diffusion at a GaAs/AlGaAs interface measured with a single quantum-dot nanoprobe
A. E. Nikolaenko, E. A. Chekhovich, M. N. Makhonin, I. W. Drouzas, A. B. Van’kov, J. Skiba-Szymanska, M. S. Skolnick, P. Senellart, D. Martrou, A. Lemaître, and A. I. Tartakovskii
Physical Review B 79 081303(R) (2009) http://dx.doi.org/10.1103/PhysRevB.79.081303
Voltage-controlled nuclear polarization switching in a single InGaAs quantum dot
M. N. Makhonin, J. Skiba-Szymanska, M. S. Skolnick, H.-Y. Liu, M. Hopkinson, and A. I. Tartakovskii
Physical Review B 79 125318 (2009) http://dx.doi.org/10.1103/PhysRevB.79.125318
Nuclear spin pumping under resonant optical excitation in a quantum dot
M. N. Makhonin, A. I. Tartakovskii,A. Ebbens, M. S. Skolnick, A. Russell, V. I. Fal’ko and M. Hopkinson
Applied Physics Letters 93 073113 (2008) http://dx.doi.org/10.1063/1.2958221
Long nuclear spin polarization decay times controlled by optical pumping in individual quantum dots
M. N. Makhonin, A. I. Tartakovskii, A. B. Van’kov, I. Drouzas, T. Wright, J. Skiba-Szymanska, A. Russell, V. I. Fal’ko, M. S. Skolnick, H.-Y. Liu, M. Hopkinson
Physical Review B 77 125307 (2008) http://link.aps.org/doi/10.1103/PhysRevB.77.125307
Overhauser effect in individual InP/GaxIn1−xP dots
J. Skiba-Szymanska, E. A. Chekhovich, A. E. Nikolaenko, A. I. Tartakovskii, M. N. Makhonin, I. Drouzas, M. S. Skolnick, and A. B. Krysa
Physical Review B 77 165338 (2008) http://link.aps.org/abstract/PRB/v77/e165338
Bistability of optically induced nuclear spin orientation in quantum dots
A. Russell, Vladimir I. Fal’ko, A. I. Tartakovskii, M. S. Skolnick
Physical Review B 76 195310 (2007) http://link.aps.org/doi/10.1103/PhysRevB.76.195310
Nuclear Spin Switch in Semiconductor Quantum Dots
A. I. Tartakovskii, T. Wright, A. Russell, V. I. Fal'ko, A. B. Van'kov, J. Skiba-Szymanska, I. Drouzas, R. S. Kolodka, M. S. Skolnick, P. W. Fry, A. Tahraoui, H.-Y. Liu, and M. Hopkinson
Physical Review Letters 98 026806 (2007) http://link.aps.org/abstract/PRL/v98/e026806

Last updated Monday, 20th May 2013

Low Dimensional Structures and Devices