ERC Starting Grant Heattronics
Heattronics is a Starting
Grant research project supported by the European Research Council.
This project has received funding from the European Union’s Seventh
Framework Programme for research, technological development and
demonstration under grant agreement no 240362-Heattronics.
Project duration: 1.1. 2010 - 31.12. 2015.
Principal investigator of the project: Tero Heikkilä.
The major outcomes of the project are explained below. The list
includes almost all papers published within this project.
Temperature, energy and work fluctuations
We have constructed the theory and analyzed the statistics of the
fluctuations of temperature in small electronic islands. Such
fluctuations are the primary source of error for hot-electron
calorimeters and bolometers, but they are also interesting in
themselves, as they reveal the stochastic transport of energy
carried by electrons, which is in some cases quite different from
the stochastic transport of charge.
We have also constructed a generic approach for calculating the
quantum statistics of work and heat fluctuations in open systems.
Publications related to this project:
- Mihail Silaev, Tero T.
Heikkilä, and Pauli Virtanen,
Lindblad-equation approach for the full counting statistics
of work and heat in driven quantum systems
Phys.
Rev.
E 90, 022103 (2014) [arXiv:1312.3476]
- V.J. Kauppila, M.A. Laakso, and
Tero T. Heikkilä
Energy and particle number fluctuations in superconducting
heterostructures
Proceedings
of
the 22nd International Conference on Noise and Fluctuations
2013 [arXiv:1306.0375]
- M.A. Laakso
Temperature Fluctuations and
Heat Transport in Nanoelectronics
Doctoral dissertation, Aalto University, 2012
- M.A. Laakso, T.T. Heikkilä, and
Yu. V. Nazarov
Theory of temperature fluctuation statistics in
superconductor-normal metal tunnel structures
Phys.
Rev.
B 85, 184521 (2012) [arXiv:1110.6726]
- M.A. Laakso, T.T. Heikkilä, and
Yu. V. Nazarov
Manifestly non-Gaussian fluctuations in
superconductor-normal metal tunnel nanostructures
Phys.
Rev.
Lett. 108, 067002 (2012).
[arXiv:1111.0149]
- M.A. Laakso, T.T. Heikkilä, and
Yu. V. Nazarov
Giant current fluctuations in an overheated single-electron
transistor
Phys.
Rev.
B 82, 205316 (2010). [arXiv:1009.3400]
- M.A. Laakso, T.T. Heikkilä, and
Yuli Nazarov
Fully Overheated Single-Electron Transistor
Phys.
Rev.
Lett. 104, 196805 (2010). [arXiv:0912.2832]
See the Synopsis
in
Physics.
- Tero T. Heikkilä and Yuli
Nazarov
Statistics of temperature fluctuations in an
electron system out of equilibrium
Phys.
Rev.
Lett. 102, 130605 (2009) [arXiv:0812.1142]
(published before the start of the ERC grant)
Superconducting junctions
Junctions between superconductors and normal metals or ferromagnets
are interesting for their heat transport properties, because of the
presence of the gap in the density of states in a superconductor.
Such a gap allows for finding strong thermoelectric-type response
from these junctions. Before our work it was thought that only
cooling is possible with these junctions, not the reciprocal process
of creating a thermovoltage. We showed that the presence of
ferromagnetic elements allows making these junctions as extremely
efficient thermoelectrics. This prediction was experimentally
verified in fall 2015, see this paper. Our work
also helped to understand the
observation of an anomalously large spin-flip length in
superconductors in the presence of spin splitting, and we have
recently predicted how this physics would be visible under a
thermoelectric response to a radio-frequency radiation. Besides, we
have analyzed temperature fluctuations in superconductors (for
publications, see previous topic) and the microwave response of
superconductor-normal-metal-superconductor junctions. Experiments on
the latter existed from the 1970's, but prior to us there was no
satisfactory theory explaining the experimental results. Our work
has been the pioneering one to explain the high-frequency properties
of such junctions, and later they have been extended also by others
in an attempt to understand the use of superconducting junctions for
quantum computing.
Publications on thermoelectric response and the nonequilibrium
physics of superconductors under spin injection and spin splitting:
- P. Virtanen, T.T. Heikkilä and F.S. Bergeret
Stimulated quasiparticles in spin-split superconductors
Phys Rev.
B 93, 014512 (2016) arXiv:1511.00817
- M. Silaev, P. Virtanen, F.S. Bergeret, and T.T. Heikkilä
Long-Range Spin Accumulation from Heat Injection in Mesoscopic
Superconductors with Zeeman Splitting
Phys.
Rev. Lett. 114, 167002 (2015) [arXiv:1411.7426]
- F. Giazotto, T.T. Heikkilä, and
F.S. Bergeret,
Very large thermophase in ferromagnetic Josephson junctions
Phys.
Rev. Lett. 114, 067001 (2015)
[arXiv:1403.1231]
- A. Ozaeta, P. Virtanen, F.S.
Bergeret, and Tero T. Heikkilä
Predicted very large thermoelectric effects in
ferromagnet-superconductor junctions in the presence of a
spin-splitting field
Phys.
Rev.
Lett. 112, 057001 (2014)
[arXiv:1307.4672]
- V.J. Kauppila, H.Q. Nguyen, and
Tero T. Heikkilä
Non-equilibrium and proximity effects in
superconductor-normal metal junctions
Phys. Rev. B 88, 075428 (2013)
[arXiv:1304.1288]
Publications on the microwave response of SNS junctions:
- J. Voutilainen
Nanocircuits
with
Superconductivity: Nonequilibrium Studies
Doctoral dissertation, Aalto University (2012)
- J. Voutilainen, P. Virtanen, and
T.T. Heikkilä
Absorption of heat into a superconductor-normal
metal-superconductor junction from a fluctuating environment
Phys.
Rev.
Lett. 109, 067002 (2012).
[arXiv:1202.3358]
- F.S. Bergeret, P. Virtanen, A.
Ozaeta, T.T. Heikkilä, and J.C. Cuevas
Supercurrent and Andreev bound state dynamics in
superconducting quantum point contacts under microwave
irradiation
Phys.
Rev. B 84, 054504 (2011) [arXiv:1105.1016].
- F. Chiodi, M. Ferrier, K.
Tikhonov, P. Virtanen, T.T. Heikkilä, M. Feigelman, S. Guéron,
and H. Bouchiat
Probing the dynamics of Andreev states in a coherent
Normal/Superconducting ring
Sci.
Rep.
1, 3 (2011) [arXiv:1005.0406]
- P. Virtanen, F.S. Bergeret, J.C.
Cuevas, and T.T. Heikkilä
Linear AC response of diffusive SNS junctions
Phys.
Rev.
B 83, 144514 (2011) [arXiv:1012.4294].
- F.S. Bergeret, P. Virtanen,
T.T. Heikkilä, and J.C. Cuevas
Theory of Microwave-Assisted Supercurrent in quantum point
contacts
Phys.
Rev.
Lett. 105, 117001 (2010) [arXiv:1006.3181].
- P. Virtanen, T.T. Heikkilä, F.S.
Bergeret, and J.C. Cuevas
Theory of Microwave-Assisted Supercurrent in Diffusive SNS
Junctions
Phys.
Rev.
Lett. 104, 247003 (2010) [arXiv:1001.5149]
- Juha Voutilainen, Matti A.
Laakso, and Tero T. Heikkilä
Physics of the proximity Josephson sensor
J. Appl.
Phys. 107, 064508 (2010). [arXiv:0906.5470]
We have also analyzed the heat conductance through a small
superconductor in good contact with normal metals:
In an effort to extend the analysis
of nonequilibrium effects in spin-split superconductors to
systems containing anisotropic (Rashba or Dresselhaus)
spin-orbit scattering, we have studied the properties of
diffusive Josephson weak links in the presence of such intrinsic
spin-orbit interaction:
Optomechanical
systems
Together with experimentalists working on optomechanical systems, we
have analyzed the quantum limits and quantum fluctuations in
optomechanical systems. The major results are on demonstrating
near-quantum-limited amplification of microwave signals using
optomechanics, and both prediction and measurement of a huge
optomechanical coupling exploiting the Josephson effect. The
connection to heattronics here is due to the fact that the
mechanical resonator is a bulky object, and it typically resides
away from its ground state. Therefore, we need to analyze what
determines the (thermal) state of the resonator. The publications on
this are:
- Raphael Khan
Nonlinearities
and quantum phenomena in nanoelectromechanical systems
Doctoral dissertation, Aalto University (2015)
- R. Khan, F. Massel and T.T. Heikkilä
Cross-Kerr nonlinearity in optomechanical systems
Phys.
Rev. A 91, 043822 (2015) [arXiv:1501.02092]
- J.-M. Pirkkalainen, S.U. Cho, F. Massel, J. Tuorila, T.T.
Heikkilä, P.J. Hakonen, and M.A. Sillanpää
Cavity optomechanics mediated by a quantum two-level system
Nature Commun. 6,
6981 (2015) [arXiv:1412:5518]
- T.T. Heikkilä, F. Massel, J.
Tuorila, R. Khan, and M.A. Sillanpää,
Enhancing optomechanical coupling via the Josephson effect
Phys.
Rev. Lett. 112, 203603 (2014)
[arXiv:1311.3802]
- Raphaël Khan, Francesco Massel,
and Tero T. Heikkilä
Tension-induced non-linearities of flexural modes in
nanomechanical resonators
Phys.
Rev.
B 87, 235406 (2013). [arXiv:1211.4363]
- Francesco Massel, Sung Un Cho,
Juha-Matti Pirkkalainen, Pertti J. Hakonen, Tero T. Heikkilä
and Mika A. Sillanpää
Multimode circuit optomechanics near the quantum limit
Nature
Commun.
3, 987 (2012). [arXiv:1205.3106]
- Francesco Massel, T.T. Heikkilä,
J.-M. Pirkkalainen, S.U. Cho, H. Saloniemi, P.J. Hakonen, and
Mika A. Sillanpää
Microwave amplification with nanomechanical resonators
Nature
480, 351-354 (2011) [arXiv:1107.4903]
- Mika A. Sillanpää, Raphaël
Khan, T.T. Heikkilä, and P.J. Hakonen
Macroscopic quantum tunneling in nanoelectromechanical
systems
Phys.
Rev.
B 84, 195433 (2011). Editor's suggestion [arXiv:1105.3318].
Spintronics and
superconductor-ferromagnet systems
We have analyzed different types of non-equilibrium effects in
spintronic systems, including spin injection into superconductors
and the different energy relaxation processes. The main results here
concern the analysis of the spin Hanle effect in superconductors,
prediction of the length/time scale for the relaxation of spin heat
accumulation, along with the discussion of its specific definition,
and a prediction of how shot noise in a spin valve would behave in
the limit of strong electron-electron energy relaxation.
- P. Virtanen, T.T. Heikkilä and F.S. Bergeret
Stimulated quasiparticles in spin-split superconductors
Phys Rev.
B 93, 014512 (2016) arXiv:1511.00817
- M. Silaev, P. Virtanen, F.S. Bergeret, and T.T. Heikkilä
Long-Range Spin Accumulation from Heat Injection in Mesoscopic
Superconductors with Zeeman Splitting
Phys.
Rev. Lett. 114, 167002 (2015) [arXiv:1411.7426]
- F. Giazotto, T.T. Heikkilä, and
F.S. Bergeret,
Very large thermophase in ferromagnetic Josephson junctions
Phys.
Rev. Lett. 114, 067001 (2015)
[arXiv:1403.1231]
- M. Silaev, P. Virtanen, T.T.
Heikkilä, and F.S. Bergeret
Spin Hanle effect in mesoscopic superconductors
Phys. Rev. B 91,
024506 (2015) [arXiv:1408.1632]
- Tero T. Heikkilä and K.E. Nagaev
Non-universal shot noise in quasiequilibrium spin valves
Phys.
Rev.
B 87, 235411 (2013) [arXiv:1302.1372]
- Tero T. Heikkilä, Moosa Hatami
and Gerrit E.W. Bauer
Spin heat accumulation and its relaxation in spin valves
Phys.
Rev.
B 81, 100408(R) (2010), Editor's suggestion [arXiv:0910.4867]
- Tero T. Heikkilä, Moosa Hatami
and Gerrit E.W. Bauer
Electron-electron interaction induced spin thermalization
in quasi-low-dimensional spin valves
Solid
State Communications 150, 475 (2010). [arXiv:1004.3656]
Graphene
We have analyzed energy relaxation processes in graphene, especially
those related with electron-phonon scattering. We also identified a
novel type of an energy relaxation mechanism across
graphene-superconductor junctions mediated by electron-electron
interactions in high-impedance graphene wires. The publications here
are:
Popular articles
We have written two popular articles reviewing recent experiments on
thermoelectric effects:
Topological media
As a side project, we have started a study of topological flat band
systems, for example predicting the possibility of very
high-temperature superconductivity in such systems. Such flat band
systems are expected to have strong fluctuation effects, which
bridges the studies of these systems to Heattronics. The publications on this topic are:
- V.J. Kauppila, F. Aikebaier, and T.T. Heikkilä
Flat band superconductivity in strained Dirac materials
Submitted to Physical Review Letters [arXiv:1601.04505]
- T.T. Heikkilä and G.E. Volovik
Flat bands as a route to high-temperature superconductivity in
graphite
Submitted as a chapter to the book on "Basic Physics of
functionalized Graphite" [arXiv:1504.05824]
- V. Kauppila, T. Hyart, and T.T. Heikkilä
Collective amplitude mode fluctuations in a flat band
superconductor
Phys.
Rev. B 93, 024505 (2016) arXiv:1505.02670
- T.T. Heikkilä and G.E. Volovik
Nexus and Dirac lines in topological materials
New J.
Phys. 17, 093019 (2015) [arXiv:1505.03277]
- P. Esquinazi, T.T. Heikkilä,
Yury V. Lysogorskiy, Dmitrii A. Tayurskii, and G.E. Volovik
On the superconductivity of graphite interfaces
Pis'ma
v ZhETF 100, 374 (2014), JETP
Lett. 100, 336 (2014) [arXiv:1407.2060]
- A. Ballestar, T.T. Heikkilä, and
P. Esquinazi,
Interface size dependence of the Josephson critical behaviour
in pyrolytic graphite
Supercond.
Sci. Technol. 27, 115014 (2014) [arXiv:1401.4959]
- N.B. Kopnin and Tero T. Heikkilä
Surface superconductivity in rhombohedral graphite
Ch. 9 in "Carbon-based
new superconductors - towards high temperature
superconductivity" (Edited by Junji Haruyama, Pan
Stanford 2014) [arXiv:1210.7075]
- Tero T. Heikkilä, Nikolai B.
Kopnin, and G.E. Volovik
Flat bands in topological media
Pis'ma
v
ZhETF 94, 252 (2011) and JETP
Lett.
94, 233 (2011) [arXiv:1012.0905]
- Nikolai B. Kopnin, Tero T.
Heikkilä, and G.E. Volovik
High-temperature surface superconductivity in topological
flat-band systems
Phys
Rev
B
83, 220503(R) (2011) [arXiv:1103.2033]
- Tero T. Heikkilä and G.E.
Volovik
Dimensional crossover in topological matter: Evolution of
the multiple Dirac point in the layered system to the flat
band on the surface
Pis'ma
v
ZhETF 93, 63-68 (2011) JETP
Lett.
93, 59-65 (2011) [arXiv:1011.4185]
- Tero T. Heikkilä and G.E.
Volovik
Fermions with cubic and quartic spectrum
Pis'ma
v
ZhETF 92, 751 (2010) JETP
Lett.
92, 681-686 (2010) [arXiv:1010.0393]
Cold atom systems
Systems of ultracold atoms trapped by laser fields is an important
platform for doing quantum simulations of materials and their
properties. Recent experimental results in this field also connect
very closely to heattronics. A postdoctoral researcher employed in
this project also worked on the theory of cold atom systems. The
publications on this topic are:
- J. Kajala, F. Massel, and P. Törmä,
Expansion Dynamics in the One-Dimensional Fermi-Hubbard Model
Phys.
Rev. Lett. 106, 206401 (2011)
- J. Kajala, F. Massel, and P. Törmä,
Expansion dynamics of the Fulde-Ferrell-Larkin-Ovchinnikov state
Phys.
Rev. A 84, 041601 (2011)
- J. Kajala, F. Massel, and P. Törmä,
Collision of one dimensional (1D) spin polarized Fermi gases in
an optical lattice
Eur.
Phys. J. D 65, 91 (2011)
Last modified 22nd February 2016