Cooling and heat transport in low dimensional phonon systems, superconductors and silicon

Juha Muhonen

Cooling and heat transport in low dimensional phonon systems, superconductors and silicon

Julkaisun otsikon käännös: Jäähdytys ja lämmönjohtuminen matala-ulotteisissa hilasysteemeissä, suprajohteissa ja piissä

Juha Muhonen

Tutkimustuotos: Doctoral Thesis › Collection of Articles

Abstrakti

Nykyisin voidaan rutiininomaisesti aikaansaada lämpötiloja 0,1 kelvinin alapuolella. Tekniikat näiden lämpötilojen saavuttamiseksi pohjautuvat joko heliumin harvinaisen ja kalliin isotoopin sekoittamiseen heliumin yleisemmän isotoopin kanssa (laimennusjäähdytin) tai paramagneettisen suolan adiabaattiseen demagnetisointiin (ADR). Nämä tekniikat ovat vakiinnuttaneet asemansa, mutta ovat liian monimutkaisia käyttöön erikoistuneiden laboratorioiden ulkopuolella. Tutkimus tässä väitöskirjassa liittyy lupaavaan sähköiseen vaihtoehtoon näille tekniikoille: normaalimetalli-eriste-suprajohde (NES) liitoksiin. Yksi suprajohteen määrittävistä tekijöistä on aukko sen elektronien tilatiheydessä. Tämän ominaisuuden takia suprajohde voi toimia energiasuodattimena elektroneille. Kun sopiva jännite asetetaan NES liitoksen yli, normaalimetalliosa jäähtyy tämän suodatusefektin johdosta. NES liitosten jäähdytysominaisuudet osoitettiin kokeellisesti jo kaksi vuosikymmentä sitten. Tällöin niillä saavutettiin noin pikowatin jäähdytysteho. Nykyisin ollaan päästy muutamiin satoihin pikowatteihin. Tämä työ jakautuu kolmeen osa-alueeseen, jotka kaikki liittyvät NES-liitoksiin. Ensinnäkin tutkimme kuinka NES-liitoksilla voidaan jäähdyttää yksi- ja kaksiulotteisia hilarakenteita. Yksiulotteisen hilan (palkin) jäähdyttäminen taas voisi auttaa NES-jäähdytystekniikkaa yleistymään. Sähköisesti jäähdytetty kalvo tarjoaisi alustan, jolle esimerkiksi säteilynilmaisimia tai suprajohtavaa elektroniikkaa voitaisiin integroida. Toiseksi tutkimme NES-jäähdytyksen rajoittavia tekijöitä. Kun toinen puoli liitoksesta (normaalimetalli) jäähtyy, toinen puoli (suprajohde) lämpiää moninkertaisella teholla. Tämä lämmitysteho voi heikentää suprajohtavia ominaisuuksia ja lämmittää hilarakennetta liitoksen lähellä. Nämä ilmiöt alentavat liitoksen jäähdytystehoa ja ovat yksi vakavimmista esteistä NES liitosten jäähdytystehon kasvattamiselle. Tutkimme näitä efektejä sekä kokeellisesti että numeerisesti. Kolmanneksi tutkimme piin jäähdyttämistä suprajohtavilla tunneliliitoksilla. Tällaisissa suprajohde-puolijohde liitoksissa NES liitoksen normaalimetalliosa on korvattu korkeasti seostetulla puolijohteella. Erityisesti tutkimme miten piin hilarakenteeseen kohdistuva jännitys vaikuttaa piin elektroni-fononi vuorovaikutukseen, ja näin ollen jäähdytykseen näissä rakenteissa.

Julkaisun otsikon käännös	Jäähdytys ja lämmönjohtuminen matala-ulotteisissa hilasysteemeissä, suprajohteissa ja piissä
Alkuperäiskieli	Englanti
Pätevyys	Tohtorintutkinto
Myöntävä instituutio	Aalto-yliopisto
Valvoja/neuvonantaja	Kaivola, Matti, Vastuuprofessori Pekola, Jukka, Ohjaaja
Kustantaja	Aalto University
Painoksen ISBN	978-952-60-4669-3
Sähköinen ISBN	978-952-60-4670-9
Tila	Julkaistu - 2012
OKM-julkaisutyyppi	G5 Artikkeliväitöskirja

Tutkimusalat

tunneliliitokset
suprajohtavuus
jäähdytys
lämmönjohtuminen
elektronifononi vuorovaikutus

Pääsy asiakirjaan

http://urn.fi/URN:ISBN:978-952-60-4670-9

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@phdthesis{36d44a689d2a4c918402dcef7f123f5c,

title = "Cooling and heat transport in low dimensional phonon systems, superconductors and silicon",

abstract = "Temperatures below 0.1 kelvin can be nowadays routinely attained. The methods for achieving these temperatures rely on either mixing the rare and expensive isotope of helium with the more common isotope (dilution refrigerator) or on adiabatic demagnetisation of paramagnetic salt (ADR). Although both of these methods are mature, they still remain complicated enough to limit the usage only to specialized laboratories. The research done in this thesis revolves around a promising electronic alternative to these techniques; normal metal-insulator-superconductor (NIS) junctions. One of the defining properties of a superconductor is a gap in its electronic density of states. This gap enables it to act as an energy filter for electrons. Because of this property, when a proper bias voltage is applied over a NIS junction the normal metal part will cool down as current passes the junction. The cooling properties of NIS junctions were demonstrated almost two decades ago with cooling powers of the order of one picowatt. At present cooling powers of few hundreds of picowatts have been achieved. This thesis describes research on three areas related to NIS junctions. Firstly we use NIS junctions to cool low dimensional lattice systems, both 1D and 2D. The cooling of a 1D lattice (beam) is interesting for fundamental research. The 2D lattice cooling (membrane) is aimed at bringing NIS devices closer to more widespread use. An electronically cooled membrane would offer a platform on which applications, such as radiation detectors or superconducting electronics, could be integrated. Secondly we focus on the limitations of NIS cooling. In all cooling, one of the main problems is the dissipation of the extracted heat. As the other side of the junction (normal metal) is cooled, the other side (superconductor) is heated with many times larger power. This heat can then weaken the superconducting properties and heat up the phonon system around the junction. These effects act to counter the cooling effect and have been one of the main obstacles in scaling up the cooling power of NIS devices. We study these effects both numerically and experimentally. Thirdly, we study the cooling of silicon with superconducting tunnel junctions. In these superconductor-semiconductor structures the normal metal in a NIS structure is replaced with highly doped silicon. Specifically we study the effects of induced lattice strain to the electron-phonon coupling in silicon and hence to the cooling properties of these structures.",

keywords = "tunnel junctions, superconductivity, cooling, heat transport, electron-phonon coupling, tunneliliitokset, suprajohtavuus, j{\"a}{\"a}hdytys, l{\"a}mm{\"o}njohtuminen, elektronifononi vuorovaikutus, tunnel junctions, superconductivity, cooling, heat transport, electron-phonon coupling",

author = "Juha Muhonen",

year = "2012",

language = "English",

isbn = "978-952-60-4669-3",

series = "Aalto University publication series DOCTORAL DISSERTATIONS",

publisher = "Aalto University",

number = "82",

address = "Finland",

school = "Aalto University",

}

TY - BOOK

T1 - Cooling and heat transport in low dimensional phonon systems, superconductors and silicon

AU - Muhonen, Juha

PY - 2012

Y1 - 2012

N2 - Temperatures below 0.1 kelvin can be nowadays routinely attained. The methods for achieving these temperatures rely on either mixing the rare and expensive isotope of helium with the more common isotope (dilution refrigerator) or on adiabatic demagnetisation of paramagnetic salt (ADR). Although both of these methods are mature, they still remain complicated enough to limit the usage only to specialized laboratories. The research done in this thesis revolves around a promising electronic alternative to these techniques; normal metal-insulator-superconductor (NIS) junctions. One of the defining properties of a superconductor is a gap in its electronic density of states. This gap enables it to act as an energy filter for electrons. Because of this property, when a proper bias voltage is applied over a NIS junction the normal metal part will cool down as current passes the junction. The cooling properties of NIS junctions were demonstrated almost two decades ago with cooling powers of the order of one picowatt. At present cooling powers of few hundreds of picowatts have been achieved. This thesis describes research on three areas related to NIS junctions. Firstly we use NIS junctions to cool low dimensional lattice systems, both 1D and 2D. The cooling of a 1D lattice (beam) is interesting for fundamental research. The 2D lattice cooling (membrane) is aimed at bringing NIS devices closer to more widespread use. An electronically cooled membrane would offer a platform on which applications, such as radiation detectors or superconducting electronics, could be integrated. Secondly we focus on the limitations of NIS cooling. In all cooling, one of the main problems is the dissipation of the extracted heat. As the other side of the junction (normal metal) is cooled, the other side (superconductor) is heated with many times larger power. This heat can then weaken the superconducting properties and heat up the phonon system around the junction. These effects act to counter the cooling effect and have been one of the main obstacles in scaling up the cooling power of NIS devices. We study these effects both numerically and experimentally. Thirdly, we study the cooling of silicon with superconducting tunnel junctions. In these superconductor-semiconductor structures the normal metal in a NIS structure is replaced with highly doped silicon. Specifically we study the effects of induced lattice strain to the electron-phonon coupling in silicon and hence to the cooling properties of these structures.

AB - Temperatures below 0.1 kelvin can be nowadays routinely attained. The methods for achieving these temperatures rely on either mixing the rare and expensive isotope of helium with the more common isotope (dilution refrigerator) or on adiabatic demagnetisation of paramagnetic salt (ADR). Although both of these methods are mature, they still remain complicated enough to limit the usage only to specialized laboratories. The research done in this thesis revolves around a promising electronic alternative to these techniques; normal metal-insulator-superconductor (NIS) junctions. One of the defining properties of a superconductor is a gap in its electronic density of states. This gap enables it to act as an energy filter for electrons. Because of this property, when a proper bias voltage is applied over a NIS junction the normal metal part will cool down as current passes the junction. The cooling properties of NIS junctions were demonstrated almost two decades ago with cooling powers of the order of one picowatt. At present cooling powers of few hundreds of picowatts have been achieved. This thesis describes research on three areas related to NIS junctions. Firstly we use NIS junctions to cool low dimensional lattice systems, both 1D and 2D. The cooling of a 1D lattice (beam) is interesting for fundamental research. The 2D lattice cooling (membrane) is aimed at bringing NIS devices closer to more widespread use. An electronically cooled membrane would offer a platform on which applications, such as radiation detectors or superconducting electronics, could be integrated. Secondly we focus on the limitations of NIS cooling. In all cooling, one of the main problems is the dissipation of the extracted heat. As the other side of the junction (normal metal) is cooled, the other side (superconductor) is heated with many times larger power. This heat can then weaken the superconducting properties and heat up the phonon system around the junction. These effects act to counter the cooling effect and have been one of the main obstacles in scaling up the cooling power of NIS devices. We study these effects both numerically and experimentally. Thirdly, we study the cooling of silicon with superconducting tunnel junctions. In these superconductor-semiconductor structures the normal metal in a NIS structure is replaced with highly doped silicon. Specifically we study the effects of induced lattice strain to the electron-phonon coupling in silicon and hence to the cooling properties of these structures.

KW - tunnel junctions

KW - superconductivity

KW - cooling

KW - heat transport

KW - electron-phonon coupling

KW - tunneliliitokset

KW - suprajohtavuus

KW - jäähdytys

KW - lämmönjohtuminen

KW - elektronifononi vuorovaikutus

KW - tunnel junctions

KW - superconductivity

KW - cooling

KW - heat transport

KW - electron-phonon coupling

M3 - Doctoral Thesis

SN - 978-952-60-4669-3

T3 - Aalto University publication series DOCTORAL DISSERTATIONS

PB - Aalto University

ER -

Cooling and heat transport in low dimensional phonon systems, superconductors and silicon

Abstrakti

Tutkimusalat

Pääsy asiakirjaan

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