Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session R23: Charge and Heat Transport at the NanoscaleInvited
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Sponsoring Units: DCMP Chair: Charles Stafford, University of Arizona Room: New Orleans Theater B |
Thursday, March 16, 2017 8:00AM - 8:36AM |
R23.00001: Local probing of thermal energy transfer and conversion processes in VO2 nanostructures Invited Speaker: Fabian Menges Nanostructures of strongly correlated materials, such as metal-insulator transition (MIT) oxides, enable unusual coupling of charge and heat transport. Hence, they provide an interesting pathway to the development of non-linear thermal devices for active heat flux control. Here, we will report the characterization of local thermal non-equilibrium processes in vanadium dioxide (VO2) thin films and single-crystalline nanobeams. Using a scanning thermal microscope and calorimetric MEMS platforms, we studied the MIT triggered by electrical currents, electrical fields, near-field thermal radiation and thermal conduction. Based on out recently introduced scanning probe thermometry method, which enables direct imaging of local Joule and Peltier effects, we quantified self-heating processes in VO2 memristors using the tip of a resistively heated scanning probe both as local sensor and nanoscopic heat source. Finally, we will report on recent approaches to build radiative thermal switches and oscillators using VO2 nanostructures. We quantified variations of near-field radiative thermal transport between silicon dioxide and VO2 down to nanoscopic gap sizes, and will discuss its implications for the development of phonon polariton based radiative thermal devices. [Preview Abstract] |
Thursday, March 16, 2017 8:36AM - 9:12AM |
R23.00002: Charge and Heat Transport in Nanoscale Junctions Invited Speaker: Pramod Reddy |
Thursday, March 16, 2017 9:12AM - 9:48AM |
R23.00003: Nanoscale thermal imaging of dissipation in quantum systems and in encapsulated graphene Invited Speaker: Dorri Halbertal Energy dissipation is a fundamental process governing the dynamics of physical systems. In condensed matter physics, in particular, scattering mechanisms, loss of quantum information, or breakdown of topological protection are deeply rooted in the intricate details of how and where the dissipation occurs. Despite its vital importance the microscopic behavior of a system is usually not formulated in terms of dissipation because the latter is not a readily measureable quantity on the microscale. While the motivation is clear, existing thermal imaging methods lack the necessary sensitivity and are unsuitable for low temperature operation required for the study of quantum systems. We developed a superconducting quantum interference nano thermometer device with sub 50 nm diameter that resides at the apex of a sharp pipette and provides scanning cryogenic thermal sensing with four orders of magnitude improved thermal sensitivity of below 1 uK/sqrtHz [1]. The noncontact noninvasive thermometry allows thermal imaging of very low nanoscale energy dissipation down to the fundamental Landauer limitý of 40 fW for continuous readout of a single qubit at 1 GHz at 4.2 K. These advances enable observation of dissipation due to single electron charging of individual quantum dots in carbon nanotubes, opening the door to direct imaging of nanoscale dissipation processes in quantum matter. In this talk I will describe the technique and present a study of hBN encapsulated graphene which reveals a novel dissipation mechanism due to atomic-scale resonant localized states at the edges of graphene. These results provide a direct valuable glimpse into the electron thermalization process in systems with weak electron-phonon interactions. [1] D. Halbertal, J. Cuppens, M. Ben Shalom, L. Embon, N. Shadmi, Y. Anahory, H. R. Naren, J. Sarkar, A. Uri, Y. Ronen, Y. Myasoedov, L. S. Levitov, E. Joselevich, A. K. Geim {\&} E. Zeldov, Nature (2016), http://dx.doi.org/10.1038/nature19843. [Preview Abstract] |
Thursday, March 16, 2017 9:48AM - 10:24AM |
R23.00004: Imaging currents in two-dimensional quantum materials Invited Speaker: Katja C. Nowack Magnetic imaging is uniquely suited to the non-invasive imaging of current densities, particularly in two-dimensional devices. In this talk, I will showcase this approach by discussing measurements on HgTe quantum well devices in the quantum spin Hall (QSH) regime. In a nutshell, we scan a superconducting quantum interference device (SQUID) to obtain maps of the magnetic field produced by the current flowing in a device. From the magnetic image we reconstruct a two-dimensional current distribution with a spatial resolution of several microns. This allows us to directly visualize that most of the current is carried by the edges of the quantum well devices when tuned into their insulating gaps - a key feature of the QSH state. I will discuss routes towards improving the spatial resolution of the current images to sub-micron length scales through a combination of improved image reconstruction and smaller sensor sizes and outline opportunities for current imaging in a range of materials including graphene and magnetically doped topological insulators. [Preview Abstract] |
Thursday, March 16, 2017 10:24AM - 11:00AM |
R23.00005: Functional Theories of Heat and Charge Transport Invited Speaker: Massimiliano Di Ventra I will discuss non-equilibrium density functional theories of local temperatures and associated heat and charge currents that are particularly suited for the study of thermoelectric phenomena. In one case, I will introduce a functional theory of open quantum systems [1] that allows for the study of local temperatures by the introduction of local thermal probes. In another [2], we couple the local temperature field to an energy density operator. I will also provide predictions on the local temperature oscillations in atomic wires [3], carbon nano-ribbons and graphene junctions [4], and discuss similarities and differences between the different local temperature definitions in the strongly-correlated regime [5]. Work supported by DOE. [1] M. Di Ventra and R. D' Agosta, Phys. Rev. Lett. 98, 226403 (2007). [2] F. Eich, G. Vignale and M. Di Ventra, Phys. Rev. Lett. 112, 196401 (2014). [3] Y. Dubi and M. Di Ventra, Nano Lett. 9, 97 (2008). [4] J.P. Bergfield, M. A. Ratner, C. A. Stafford, and M. Di Ventra, Phys. Rev. B 91, 125407 (2015). [5] L.Z. Ye, D. Hou, X. Zheng, Y.J. Yan, and M. Di Ventra, Phys. Rev. B 91, 205106 (2015). [Preview Abstract] |
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