Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session K18: Electronic and Thermal Transport Phenomena in Superlattices, Nanostructures, and other Artificially Structured Materials |
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Sponsoring Units: DCMP DMP Chair: Saquib Shamim, University of Wuerzburg Room: LACC 306B |
Wednesday, March 7, 2018 8:00AM - 8:12AM |
K18.00001: CMOS compatible processing for phosphorous delta-layer nanoscale electronics DeAnna Campbell, Michael Marshall, Leon Maurer, Justin Koepke, Tzu-Ming Lu, Daniel Ward, Shashank Misra Silicon based phosphorous delta layer electrical devices are a potential pathway to high efficiency transistors. A widely known fabrication path involves scanning tunneling microscope (STM) based hydrogen lithography. We present a low temperature STM sample preparation that enables significant processing of devices prior to STM. This preparation enables a CMOS compatible fabrication path that scales from the nanoscale STM patterned device to macroscopic bond pads using only optical lithography. Using low-temperature electrical transport, we demonstrate a high yield of delta-layer based, nanoscale electrical devices across numerous fabrication runs. This work was supported by the Laboratory Directed Research and Development Program at Sandia National Laboratories, and was performed, in part, at the Center for Integrated Nanotechnologies, a U.S. DOE, Office of Basic Energy Sciences user facility. |
Wednesday, March 7, 2018 8:12AM - 8:24AM |
K18.00002: Variability of atomically precise tunnel junctions Michael Marshall, DeAnna Campbell, Leon Maurer, Justin Koepke, Tzu-Ming Lu, Daniel Ward, Shashank Misra Donor devices fabricated in silicon using the scanning tunneling microscope (STM) are used as a discovery platform for everything ranging from quantum bits to ultra-efficient tunnel field effect transistors because the underlying hydrogen lithography step can be performed with atomic precision. However, the resultant devices are not necessarily atomically perfect. Here, we examine the reliability of STM-fabricated tunnel junctions, a basic element of the many of the devices and circuits fabricated with this technique. Low-temperature electrical transport measurements are used to characterize how similar nominally identical tunnel junctions behave, compared to tunnel junctions with intentionally different geometry. This work was supported by the Laboratory Directed Research and Development Program at Sandia National Laboratories, and was performed, in part, at the Center for Integrated Nanotechnologies, a U.S. DOE, Office of Basic Energy Sciences user facility. |
Wednesday, March 7, 2018 8:24AM - 8:36AM |
K18.00003: fRG treatment of the 0.7 analog in quantum point contacts Lukas Weidinger, Christian Schmauder, Dennis Schimmel, Jan Von Delft We use a recently developed fRG method (extended coupled-ladder |
Wednesday, March 7, 2018 8:36AM - 8:48AM |
K18.00004: Transport Characteristics of Al/LAO/STO-LAO/STO Nanostructures Shan Hao, Jianan Li, Hyungwoo Lee, Jung-Woo Lee, Chang-Beom Eom, Patrick Irvin, Jeremy Levy The interface of LAO/STO supports a 2D electron gas that can be further reconfigured into nanostructures using conductive atomic force microscope lithography. As grown, LAO/STO has a critical thickness of 4 unit cells (u.c.) of LAO. By capping the surface of LAO/STO with Al, the critical thickness can be reduced from 4 u.c. to 1 u.c. Our aim is to create Al/LAO/STO nanostructures and couple to them using LAO/STO nanostructures, in order to reveal properties that might be associated with superconductivity in Al and at the at the LAO/STO interface. These devices also have the potential to be coupled to other Al-based, superconducting devices such as SQUIDs and superconducting microwave resonators. |
Wednesday, March 7, 2018 8:48AM - 9:00AM |
K18.00005: Wigner crystal of magnetic charges in neodymium-based artificial honeycomb lattice Yiyao Chen, Brock Summers, Ashutosh Dahal, Deepak Singh Antiferromagnetic artificial honeycomb lattice can be used to explore fundamental properties of solid state materials. The magnetic analogue of Wigner crystal is one of them. In this talk, we present phenomenological evidences to the development of Wigner crystal of magnetic charges in a newly designed neodymium-based artificial honeycomb lattice where effective magnetic charges of ±1 and ±3 units, bound by magnetic Coulomb's interaction, act as single particle condensates. Electronic measurements on neodymium-based two-dimensional honeycomb lattice reveal magnetic field induced two step switching process, accompanied by a colossal enhancement in differential conductivity, in a narrow temperature range of 25 K<T<60 K. Correspondingly, the system manifests a transition between two magnetic charge configurations, on the vertices of honeycomb lattice. At low temperature and field, the bound charges tend to condense in a diamagnetic state. The experimental results provide a novel mechanism to manipulate the electronic properties of magnetic materials in two dimensional systems. |
Wednesday, March 7, 2018 9:00AM - 9:12AM |
K18.00006: Non-linear susceptibility and static scaling analysis in permalloy artificial honeycomb lattice Ashutosh Dahal, Yiyao Chen, Brock Summers, Deepak Singh The artificial honeycomb lattice has evolved into a new avenue for the exploration for various novel magnetic phenomena. We have studied the temperature dependent evolution of theoretically predicted magnetic phases, e.g. spin ice, magnetic charge ordered state and the spin order, in a newly fabricated macroscopic size permalloy honeycomb lattice of ultra-small connecting elements, with a typical length of 12 nm. The ultra-small element size results in a small inter-elemental energy of ~ 15 K, thus allows us to use temperature as the feasible tuning parameter for experimental investigation purposes. In this talk, I will present new results on the scaling of non-linear susceptibilities and the associated static scaling in various temperature regimes. The results will be compared to the known scaling coefficient in geometrically frustrated magnet of three-dimensional origin. Finally, I will discuss the evolution of the spin order at low temperature in the comparative framework of other magnetic phases that arise as a function of temperature. |
Wednesday, March 7, 2018 9:12AM - 9:24AM |
K18.00007: Temperature-dependent Magnetoresistance in Platinum Metalattice Yixuan Chen, Yunzhi Liu, Jennifer Russell, Parivash Moradifar, Tom Mallouk, Nasim Alem, John Badding, Ying Liu Metalattices are artificial 3D solids periodic on a scale of 1-100nm [1]. Their structure can be viewed as meta-atoms (filled voids) connected by meta-bonds (thin channels interconnecting meta-atoms). Metalattices of platinum inverse opal fabricated by infiltrating a template assembled from silica nanospheres with diameters less than 100nm are studied in this work. The infiltration is realized by high-pressure confined chemical fluid deposition (HPcCFD), a technique capable of filling pores of diameters from a few nm to ~100nm without leaving voids over many millimeters of length. As the lattice constants are comparable to the characteristic length scales of many important physical processes – for instance, electron (in)elastic mean free paths, new 3D mesoscopic electronic phenomena may arise. We carried out magneto-electric transport measurements down to 2K on a ~1μm thick platinum metalattice. The temperature dependence of magnetoresistance was found to evolve systematically for both high and low magnetic field. Its relationship to the nanometer-scale, 3D structural ordering of metalattices will be discussed. |
Wednesday, March 7, 2018 9:24AM - 9:36AM |
K18.00008: Heat transport in the periodically confined geometries of silicon metalattices Weinan Chen, Disha Talreja, Hiu Yan Cheng, Gerald Mahan, Vincent Crespi, John Badding, Venkatraman Gopalan, Ismaila Dabo The insertion of voids of nanometer size in semiconductors provides an effective and widely applicable approach to control their thermal conductivities. We have studied the thermal properties of silicon metalattices, which consist of an array of nanometer-sized pores inserted into crystalline silicon. The heat conductivity of these nanostructures has been calculated as a function of the arrangement and radius of the pores using Green-Kubo techniques with a modified Stillinger-Weber potential, revealing an extreme reduction in the thermal conductivity of two orders of magnitude for pore radii in the range of 1 to 10 nm. We have carried out a phonon-resolved analysis to explain thermal conductance of silicon metalattices and to examine its strong nonlinear dependence as a function of the volume fraction of the pores. This analysis provides guidelines for designing semiconducting nanostructures with minimal lattice thermal conductivities towards improving heat management in microelectronics and energy conversion in thermoelectrics. |
Wednesday, March 7, 2018 9:36AM - 9:48AM |
K18.00009: Topological quantization of thermal transport in classical dimerized mechanical lattices Chih-Chun Chien, Kirill Velizhanin, Yonatan Dubi, Bojan Ilic, Michael Zwolak Topological effects from interesting band structures have been discovered in electronic systems and later on in photonic, phononic, and mechanical systems. By resorting to a resemblance between the electronic band structure of the topological quantum Su-Schrieffer-Heeger model and the vibrational spectrum of a classical dimerized mechanical lattice, we identified topological edge modes that are localized at the boundary. When the dimerized lattice is connected to two reservoirs with different temperatures, the topological edge modes drastically affect thermal conductance through the lattice. We found three quantized ratios of thermal conductance resulting from different configurations with different numbers of the edge modes. Moreover, the quantization is robust against small perturbations from disorder and non-linear effects. |
Wednesday, March 7, 2018 9:48AM - 10:00AM |
K18.00010: On-and-Off Chip Cooling of a Coulomb Blockade Thermometer down to 2.8 mK Yemliha Kalyoncu, Mario Palma, C. Scheller, Dario Maradan, Anna feshchenko, Matthias Meschke, Dominik Zumbuhl Reaching ultralow temperatures in electronic transport experiments can facilitate novel quantum matter as well as enhanced quantum coherence. Cooling nanoelectronic devices below 10 mK is a great challenge since thermal conductivities become very small, creating a pronounced sensitivity to heat leaks. Here, we overcome these difficulties by combining on-and-off chip adiabatic demagnetization. This provides direct cooling of the islands of a Coulomb blockade thermometer as well as the electrical leads connecting to the sample, thus reducing the external heat leak. The device comprises a linear array of Al/AlOx/Al tunnel junctions with huge copper islands in between, serving as spin reservoirs for demagnetization, thus enabling on-chip cooling. This scheme results in a lowest electronic temperature of 2.8 ± 0.1 mK, setting a new record for a nanoelectronic device. We also present a thermal model which gives a good qualitative account and suggests how to overcome the main limitations to cool below 1 mK, thus opening the door for future microkelvin nanoelectronics. |
Wednesday, March 7, 2018 10:00AM - 10:12AM |
K18.00011: Abstract Withdrawn
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Wednesday, March 7, 2018 10:12AM - 10:24AM |
K18.00012: Dispersive Thermometry with a Josephson Junction Olli Saira, Maciej Zgirski, Klaara Viisanen, Dmitry Golubev, Jukka Pekola We have constructed a "Josephson bolometer" that detects weak electrical fluctuations and indicates the strength of these fluctuations via a shift in the frequency of a microwave resonator [1]. With this functionality, we demonstrate non-local primary thermometry by detecting the noise of a remote resistor. Importantly, even though this mode of operation resembles that of a noise thermometer, our device indicates the sensed temperature directly through a change in the phase of a microwave probe signal instead of relying on rectification with external electronics. Using a standard HEMT preamplifier, we achieve a noise-equivalent temperature of < 10 μK/√Hz at 50 mK with a power dissipation below 1 fW. |
Wednesday, March 7, 2018 10:24AM - 10:36AM |
K18.00013: Shot Noise for Electron Pairing without Superconductivity Matthias Droth, Andras Palyi Recent experiments have revealed electron pairing in superconductors outside the superconducting regime [1]. We propose and theoretically study an engineered nanostructure that allows in-situ tunability and pairing of electrons beyond the limitations of the Anderson-Holstein model [2]. Assuming a source-drain biased setup, we obtain the expected current and shot noise via full counting statistics and infer a sharp increase of the Fano factor as the system enters the phase of electron pairing. Our results can be used to verify and contribute to the understanding of electron-pairing without superconductivity. |
Wednesday, March 7, 2018 10:36AM - 10:48AM |
K18.00014: Graphene Josephson junctions in the quantum Hall regime Ruoyu Chen, Yulu Liu, Takashi Taniguchi, Kenji Watanabe, Chun Ning Lau The combination of superconductivity and quantum Hall effect is fundamentally interesting, which may decode the scattering mechanism between 1D edge channels and the superconductors, and shed light on the search of new Majorana zero modes. The main challenge is technical: sufficiently high mobility allowing quantum Hall effect resolved at a low field, and ohmic contacts that allows induction of superconducting proximity effect. Both challenges can be overcome in graphene-based devices. Furthermore, graphene hosts additional novel quantum Hall phases due to symmetry break or strong electron-electron interactions, which makes it to be unique compared with other candidates. Utilizing NbN as the contact selection to graphene channels, our initial results suggest successful proximity in its Josephson junction forms. Detailed studies further tuning the junctions as well as of other superconducting structures are ongoing, and will be discussed in this talk. |
Wednesday, March 7, 2018 10:48AM - 11:00AM |
K18.00015: A quantum-dot heat engine operated close to thermodynamic efficiency limits. Martin Josefsson, Artis Svilans, Adam Burke, Eric Hoffmann, Sofia Fahlvik, Claes Thelander, Martin Leijnse, Heiner Linke Particle-exchange heat engines extract work by using an energy filter to control a thermally driven particle flow between two or more heat reservoirs. These engines have been predicted to reach the same ideal thermodynamic efficiency limits as those accessible to classic cyclical engines, but this prediction has never been verified experimentally. In this work we realize a particle-exchange heat engine based on a quantum dot embedded in an InAs/InP nanowire. We demonstrate an efficiency at maximum power close to the Curzon-Ahlborn efficiency and at the maximum efficiency (~70% of Carnot efficiency) the QD still produces finite power output roughly equal to half of the maximal amount. These results are obtained by measuring the engine’s steady state output power and combining it with the calculated electronic heat flow. This procedure is made possible by an excellent agreement between the modelled and measured generated current, which allows for a quantitative estimate of the heat flow. |
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