Topological Phenomena in Superconducting Hybrid Structures

Alexander Golubov

Moscow Institute of Physics and Technology

and

University of Twente, Netherlands

MIPT Interdisciplinary Center for Basic ResearchAim and Tasks

Aim: Intensification of research within the ICBR laboratoriesand solve actual problems that lie at the turn of the areas of these research laboratories

Main tasks: getting advanced scientific results and their publications in

top-rated scientific journals training world-class specialists in areas related to the

research of ICBR interaction with the Centers for Applied Research at MIPT,

transfer of promising technologies for commercialization arising from interdisciplinary research of ICBR

creation of an expert world level platform on research fields of ICBR

holding of international conferences, workshops and schools in resarch areas of ICBR

MIPT Interdisciplinary Center for Basic ResearchLaboratories

Topological phenomena in superconductive systems (A.Golubov) Artificial quantum systems (O.Astafiev) Theoretical nanophysics (M.Feigelman) Terahertz spectroscopy (B.Gorshunov) Nanooptics and plasmonics (V.Volkov) Quantum nanostructures (M.Trunin)

Perspective investigations of membrane proteins (G.Bueldt) Structure biology of receptors conjugated to G-proteins (V.Cherezov) Membrane model systems for refolding and crystallization of

membrane proteins (V.Chupin) Sensory systems based on psychrophilic and mesophilic bacteria lux

operons (I.Manuhov)

Astrophysics and physics of non-linear processes (V.Beskin)

MIPT Interdisciplinary Center for Basic ResearchElectron Beam Lithography System CRESTEC-CABL-9500C

Acceleration voltage: 50 kV; Wafer Size: up to 100 mm; Beam Diameter: 2nm;Minimum Line Width: 10nm or less lines;

Stitching Accuracy: 20nm (Writing Area 60um sq.)

1910 1930 1950 1970 1990

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Supe

rcon

duct

ing

trans

ition

tem

pera

ture

(K)

Hg Pb NbNbCNbC NbNNbN

V3SiV3Si

Nb3SnNb3Sn Nb3GeNb3Ge(LaBa)CuO(LaBa)CuO

YBa2Cu3O7YBa2Cu3O7

BiCaSrCuOBiCaSrCuO

TlBaCaCuOTlBaCaCuO

HgBa2Ca2Cu3O9HgBa2Ca2Cu3O9

HgBa2Ca2Cu3O9(under pressure)HgBa2Ca2Cu3O9(under pressure)

Liquid Nitrogen temperature (77K)

MgB2

2010

Transition temperatureYBa2Cu3O7

Y

Ba

BaCu

O

TitelSuperconductivity

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Fabricated in Juelich, Germany

(T. Schappers, I. Batov)

Nb

Nb/Bi2Te3Fabricated in Twente

Examples of the nanosructures:combinations of semiconducing and ferromagnetic nanowires, 3D topological insulators, superconductors

Fabricated in ISSP RAN, Chernogolovka(group of Valery Ryazanov)

TitelSSTM (group of D. Rodichev, Paris)(Paris, France)

1.2K (He4) achievable 0.6K (He4+He3)magnetic field up to 3 Tesla

1E-10mbar

TitelNew laboratory at MIPT”Topological quantum phenomena in superconducting structures”

Megagrant 2014-2016

Our mission and goals:

- study of fundamental phenomena in hybrid systems consisting of superconductors, ferromagnets and semiconductors (nanowires, surfaces of topological insulators): theory and experiment

- development of infrastructure and technological base- strengthen collaboration with world leading groups in our field - education and training of young researches

20 members: - 3 doctors of science- 9 candidates of science- 3 PhD students- 5 master students

Output in the first half year 2014:- 7 publications, among them 4 in high impact journals Phys.Rev.Lett. and Phys.Rev B- 5 conference talks

TitelSingle-Vortex Superconducting Box: Choice of the System

CE

Pb-islands in-situ grown on Si(111))

Result: spatially separated, well-structured facetted single crystals of Pb. Selected island: size d =110nm, thickness h = 5.5nm

TitelSingle-Vortex Superconducting Box: Usadel Model

Experiment

+ Model

Vortex profile

2ξEFF

ξEFF ≈ 45 ± 2 nm

TitelS/TI/S junctions

Nb NbBi2Te3Bi2Te3

50 100 150 200 250 300 nmJunction lengths

Length

Nb: blueBi2Te3: redWidth=500 nm

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Titel

Hallmarks for a Josephson junction:1) Shapiro steps

2) Modulation Ic versus B-field

Josephson supercurrent

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TitelFirst hallmark – Shapiro steps

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• Microwave frequency ω• @2eV/ħ=nω Shapiro steps• (Energy Cooper pairs

resonant to energy microwave)

ω = 10 GHzV= n x 20.7 μVT=1.6 K

-50 0 50-300

-200

-100

0

100

Cur

rent

(A)

Voltage (V)

Increasing powershifted for clarity

Titel

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Second hallmark – Ic-B modulation

-30 -20 -10 0 10 20 300

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30

Crit

ical

cur

rent

(A)

Magnetic field (mT)

LxW 50nmx500nm

-30 -20 -10 0 10 20 300

5

10

15

20

25

30

35

Crit

ical

cur

rent

(A)

Magnetic field (mT)

LxW 100nmx500nm

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Conclusion: supercurrent is carried by surface layer, ballistic regime

Nature Materials (2012)

Link supercurrent and surface states

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0 50 100 150 200 250 300

1

10

Dirty limit, Usadel

Clean limit, Eilenberger

Measurements

Crit

ical

cur

rent

(A)

Junction length (nm)

0 1 2 3 4 5 60

5

10

15

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35 Dirty limit,

Usadel Clean limit,

Eilenberger Measurements

Crit

ical

cur

rent

(A)

Temperature(K)

TitelJosephson supercurrent has been

realized through the surface states of Bi2Te3

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Provides prospects for Majorana devices……but

What is the best topological insulator for this purpose? (stability, insulating in the bulk, Dirac

cone in the gap)What is the smoking gun experiment with 3D

topological insulators to observe Majorana fermions?