ELFT HÍRADÓ

[csonka <csonka AT dept.phy.bme.hu>]

Kedves Erdeklodok,

A BME Nanofizika szeminariuman

*Georgios Katsaros (Johannes Kepler University, Linz & IST Austria)*

tart eloadast
/*
Towards spin qubits in Ge self-assembled nanostructures*//*

*/cimmel.

*Idopont: (rendkivuli) oktober 14, szerda 11:15*
A helyszin a szokasos, F ep. I. lepcs. I. em Fizika Tanszek, 5. 
(szeminariumi) szoba.

Minden erdeklodot szeretettel latunk!

Csonka Szabolcs


*Abstract:*

SiGe nanostructures have emerged as a promising material for the 
realization of spin qubits [1]. In the past several years intense 
research has been devoted in studying QDs defined in SiGe 2DEGs [2] and 
P donors in Silicon [3]. Spin relaxation times of a few seconds and 
coherence times of close to a second have been reported [4]. On the 
other hand there are much less studies which have focused on holes and 
in particular confined in SiGe. In 2012, spin relaxation times in Ge/Si 
NW QDs were reported to be in the ms range [5] and just last year the 
dephasing time was reported to be more than one order of magnitude 
larger than that of III-V materials [6]. All these studies point out the 
importance of group-IV elements in the field of spin qubits.

In our group we study holes confined in Ge self-assembled 
nanostructures. In 2010 the first realisation of single-hole transistors 
based on individual SiGe dome islands was reported [8]. Transport 
spectroscopy revealed largely anisotropic hole g-factors. By changing 
the number of holes localized within the SiGe QDs a clear modulation of 
the g-factor was observed indicating that the g-factors are linked to 
the corresponding orbital wavefunctions. However, dual gate devices 
demonstrated that the g-factor of the same orbital wavefunction can be 
changed by more than 300% when changing the value of a perpendicular 
electric field while keeping a constant number of holes [9]. This result 
indicated that this material system might be interesting for performing 
spin manipulation by means of g-tensor modulation.

However in order to move towards the realization of spin qubits one 
needs to move away from single quantum dot devices; charge sensors and 
double quantum dots need to be realized. For achieving these two 
building blocks, we are aiming to use two different type of structures: 
a) self-organized Ge nanostructures, i.e. Ge islands grown on 
prepatterned Si [10] and b) one dimensional Ge nanowires, so called 
hut-wires [11,12]. Within this talk I will present the current status of 
research in these two directions.

References:

[1] F. A. Zwanenburg et al., Rev. Mod. Phys. 85, 961 (2013).

[2] N. Shaji et al., 
<http://apps.webofknowledge.com/OneClickSearch.do?product=UA&search_mode=OneClickSearch&colName=WOS&SID=T185JOgp49f5pIb@id7&field=AU&value=Shaji,%20N&ut=14375105&pos=%7B2%7D>Nat. 
Phys. 4, 540 (2008); B. M. Maune et al., Nature 481, 344 (2012)

[3] Morello et al. Nature 467, 687 (2010)

[4] C. B. Simmons et al, /Phys. Rev. Lett./ *106*, 156804 (2011); H. 
Büch et al. Nat. Com. 4, 2017 (2013), J. Muhonen et al., Nature 
Nanotechnology 9, 986 (2014)

[5]Y. J. Hu et al., Nat. Nanotech. 7, 47 (2012)

[6] A. P. Higginbotham et al., Nano Lett.,14, 3582 (2014)

[7] J. Stangl, V. Holý, and G. Bauer, Rev. Mod. Phys. 76, 725 (2004)

[8] G. Katsaros et al., Nature Nanotech. 5, 458 (2010)

[9] N. Ares et al., Phys. Rev. Lett. 110, 046602 (2013)

[10] E. Lausecker et al., Appl. Phys. Lett 98, 143101(2011)

[11]Z. Z. Zhang et al., Phys. Rev. Lett. 109, 085502 (2012)

[12] H. Watzinger et al., APL Materials 2, 076102 (2014)



--
Szabolcs Csonka
Nanoelectronics Laboratory, Department of Physics
Budapest University of Technology and Economics
1111 Budapest, Budafoki út 8
Building F, Entrance I, Basement 6
Phone: +36-1-4633056
Fax: +36-1-4634180
email:csonka AT mono.eik.bme.hu