Condensed Matter/Biophysics Seminars
Fall 2020

Condensed Matter/Biophysics Seminars are via Zoom until further notiice
on Mondays @ 4:05 pm to 4:55 pm

Contact: Yasu Takano or Dmitrii Maslov

August 31
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September 7 (No seminar – Labor Day)
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September 14
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September 21
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September 28
	Speaker	Samaresh Guchhait (Howard Univ.)
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	Host	Mark Meisel

October 5
	Speaker	Jiun-Haw Chu Univ. of Washington)
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	Host	James Hamlin

October 12
	Speaker	Jeremy Levy (Univ. of Pittsburgh)
	Title	TBA
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	Host	Dominique Laroche

October 19
	Speaker	Miguel Gonzalez (Aramco Americas)
	Title	From macro to micro (to nano): mechanical resonators at all scales for rheology sensing in oilfield fluids
	Abstract	Real-time monitoring of oilfield fluid rheology is of crucial importance for oil recovery. During various operations such as drilling, production, stimulation, and intervention, the rheology of the fluids being produced or injected into the well need to be monitored to ensure safe operation, or to optimize the process being carried out. However, reliably measuring their physical properties can still pose a great challenge when the fluids are part of a multiphase flow or are complex inhomogeneous fluids whose properties can vary continuously with parameters such as temperature, pressure, flow rates, and composition. While specialized commercial instruments that make comparable measurements can be found in other industries, fewer systems tailored to the oil and gas industry exist or are too costly and complex to deploy in every well. In this presentation, I will discuss two examples of viscosity/density sensing systems based on mechanically resonating devices customized to different measurement scenarios in the field. In the first example, I demonstrate a ruggedized tuning fork device for in-line measurements of viscosity and density of non-Newtonian fluids. This instrument is a robust permanent tool for surface installation with applications in quality assessment of drilling mud or other wellbore fluids such as fracturing fluids. I will also discuss techniques currently being explored to extract rheological information from the vibrational damping measured on the resonator. In the second example, I will discuss miniaturized resonators fabricated using micro/nano-machining techniques. These devices can be integrated into small-scale measurement platforms, either for downhole deployment or for lab-on-a-chip platforms useful in portable field viscometry systems.
	Host	Yoonseok Lee

October 26
	Speaker	Denis Bandurin (MIT)
	Title	Interaction-dominated transport in graphene: old mysteries and new regimes
	Abstract	Electron–electron (e–e) collisions can impact transport in a variety of surprising and sometimes counterintuitive ways. Despite long-time interest, experiments on the subject proved challenging because of the presence of momentum-relaxing scattering sources (e.g. phonons or impurities). Only recently, sufficiently clean electron systems in which transport dominated by momentum-conserving e–e collisions have become available, enabling the study of electron transport governed by interactions. This talk will begin by discussing the behaviour in monolayer graphene which by now is relatively well understood. I will show that at elevated temperatures, the behaviour of graphene’s electron fluid resembles that of classical liquids and gases with high viscosity [1,2]. I will discuss approaches that can be used to probe the transport governed by e–e interactions and talk about electron viscometry [3-4]. A very different behaviour is found for transport in twisted bilayer graphene (TBG). I will show that, unlike the case of monolayer graphene, e–e collisions in large-angle TBG can lead to the relaxation of electrical current and result in a quadratic temperature dependence of its resistivity. This surprising behaviour cannot be accounted for by existing scenarios (e.g. umklapp or multi-band scattering) and calls for alternative explanations. [1] D. A. Bandurin et al., Science 351, 1055 (2016). [2] D. A. Bandurin, A. Shytov et al., Nat. Comm. 9, 4533 (2018). [3] R. Krishna Kumar, D.A Bandurin et al., Nat. Phys. 13, 1182 (2017).[4] A.I. Berdyugin et al., Science 364, 6436, 162-165 (2019).
	Host	Dmitrii Maslov

November 2
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November 9
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November 16
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November 23
	Speaker	Chris Leighton (Univ. of Minnesota)
	Title	TBA
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	Host	Dmitrii Maslov

November 30
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December 7
	Speaker	Suchitra Sebastian (Univ. of Cambridge)
	Title	TBA
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	Host	Yasu Takano

December 14
	Speaker	Silke Buehler-Paschen (TU Wien)
	Title	TBA
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	Host	Yasu Takano

Condensed Matter/Biophysics Seminars
Spring 2021

Condensed Matter/Biophysics Seminars are via Zoom until further notice
on Mondays @ 4:05 pm to 4:55 pm

Contact: Yasu Takano or Dmitrii Maslov

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January 11
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January 18 (No seminar – MLK Jr Day)
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January 25
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February 1
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February 8
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February 15
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February 22
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March 1
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March 8
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March 15
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March 22
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March 29
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April 5
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April 12
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April 19
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