title: Study of radiative heat transfer in Ångström- and nanometre-sized gaps.
abstract: Radiative heat transfer in Ångström- and nanometre-sized gaps is of great interest because of both its technological importance and open questions regarding the physics of energy transfer in this regime. Here we report studies of radiative heat transfer in few Å to 5 nm gap sizes, performed under ultrahigh vacuum conditions between a Au-coated probe featuring embedded nanoscale thermocouples and a heated planar Au substrate that were both subjected to various surface-cleaning procedures. By drawing on the apparent tunnelling barrier height as a signature of cleanliness, we found that upon systematically cleaning via a plasma or locally pushing the tip into the substrate by a few nanometres, the observed radiative conductances decreased from unexpectedly large values to extremely small ones-below the detection limit of our probe-as expected from our computational results. Our results show that it is possible to avoid the confounding effects of surface contamination and systematically study thermal radiation in Ångström- and nanometre-sized gaps.
authors.affiliation: Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Longji
authors.initials: L
authors.lastname: Cui
authors.affiliation: Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Wonho
authors.initials: W
authors.lastname: Jeong
authors.affiliation: Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, 28049 Madrid, Spain.
authors.forename: Víctor
authors.initials: V
authors.lastname: Fernández-Hurtado
authors.affiliation: Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, 28049 Madrid, Spain.
authors.forename: Johannes
authors.identifier: 0000-0002-7972-0646
authors.initials: J
authors.lastname: Feist
authors.affiliation: Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, 28049 Madrid, Spain.|Donostia International Physics Center, 20018 Donostia/San Sebastián, Spain.
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: García-Vidal
authors.affiliation: Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, 28049 Madrid, Spain.
authors.forename: Juan Carlos
authors.identifier: 0000-0001-7421-0682
authors.initials: JC
authors.lastname: Cuevas
authors.affiliation: Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Edgar
authors.initials: E
authors.lastname: Meyhofer
authors.affiliation: Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.|Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Pramod
authors.initials: P
authors.lastname: Reddy