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That is the essence of science: ask an impertinent question, and you are on the way to a pertinent answer.

Jacob Bronowski

Colloquia

Physics Conference Room, SB B326
Coffee starts at 12:00 PM and talk starts at 12:15 PM
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9
Oct '24
Next Event
In-person
+ Online
Columbia University
Sarah Campbell
Q&A about QC-Columbia Pre-Engineering Program
This talk is accessible via Zoom or use
meeting ID 829 2687 2594 and passcode 866995 to join
21
Oct '24
In-person
+ Online
Queens College
John Terilla
Mathematical and physical ideas in the foundations of Artificial Intelligence
This talk is accessible via Zoom or use
meeting ID 829 2687 2594 and passcode 866995 to join
Abstract:
By viewing a character in a text as a particle that can occupy one of a finite collection of states (the letter “A”, the letter “T”, the number “7”, …) one can interpret samples of natural language as observations of a one-dimensional system of interacting particles.  I’ll review some of the engineering developments that led to the state-of-the-art large language models in use today and argue that the mathematical structures at work behind the scenes are consistent with this physical view and sheds a little light, not just on how LLMs work, but how human language itself might work.
 
28
Oct '24
In-person
+ Online
City College
Carlos Meriles
Near-field sensing of a topological metasurface via scanning color center microscopy
This talk is accessible via Zoom or use
meeting ID 829 2687 2594 and passcode 866995 to join
Abstract:
As the ability to control electromagnetic fields through engineered photonic structures grows, so does our need for field mapping techniques with subwavelength resolution. Here, we use a scanning diamond nanocrystal to investigate the interplay between the emission of room-temperature nitrogen-vacancy (NV) centers and a proximal topological waveguide. The NV photoluminescence serves as a local, spectrally broad light source to characterize the waveguide response, both in terms of its wavelength bandwidth as well as the correspondence between light injection site and directionality of wave propagation. Further, we find that near-field coupling between the emitters and the waveguide chiral modes influences the ellipticity of the NV photoluminescence, hence allowing us to reveal nanostructured light fields with a spatial resolution defined by the nanoparticle size. Our results pave the route to exploiting color centers as photonic sensors, an approach that also promises opportunities in the development of on-chip devices integrating single-photon emitters and quantum optics.
30
Oct '24
Ben-Gurion University of the Negev
Yonatan Dubi
The chirality induced spin-selectivity effect: a puzzle and it’s (possible) resolution
Abstract:
Zoom Seminar at the Department of Chemistry at Lehman College and the Department of Physics at Queens College

You are invited to a Zoom meeting.
When: Oct 30, 2024 12:00 PM Eastern Time (US and Canada)

Register in advance for this meeting:
https://us06web.zoom.us/meeting/register/tZEpdOqrrjIqE9NIRUSU3N3IA04w99SvB6bs

After registering, you will receive a confirmation email containing information about joining the meeting.


When electrons are injected through chiral molecules, the resulting current may become spin polarized. This effect, known as the chirality-induced spin-selectivity (CISS) effect,  has been suggested to emerge due to the interplay between spin–orbit interactions and the chirality within the molecule. However, such explanations require unrealistically large values for the molecular spin–orbit interaction without any physical justification. Put simply, to date, the physical origin of  the CISS effect is unknown.

I will present the “spinterface mechanism” for the CISS effect, based on the interplay between spin–orbit interactions in the electrode, the chirality of the molecule (which induces a solenoid field), and spin-transfer torque at the molecule–electrode interface. I will show the remarkable agreement between the spinterface theory and various experimental results, and will describe a set of “smoking gun” experiments for differentiating these mechanisms from other theoretical explanations. Finally, we will describe a spinterface mechanism for the CISS effect in photo-excited electrons scattered off a layer of chiral molecules.

 [1] S. Alwan & Y. Dubi, Spinterface Origin for the Chirality-Induced Spin-Selectivity Effect, J. Am. Chem. Soc. 143, 35, 14235–14241 (2021)

[2] Y. Dubi, Spinterface chirality-induced spin selectivity effect in bio-molecules, Chem. Sci., 13, 10878-1088 (2022).

[3] C. Yang, Y. Li, S. Zhou, Y. Guo, C. Jia, Z. Liu, K. N. Houk, Y. Dubi & X Guo, Real-time monitoring of reaction stereochemistry through single-molecule observations of chirality-induced spin selectivity, Nature Chemistry 15, 972–979 (2023)

[4] Seif Alwan, Subhajit Sarkar, Amos Sharoni, Yonatan Dubi, Temperature-dependence of the CISS effect from measurements in Chiral molecular intercalation super-lattices, J. Chem. Phys. 159, 014106 (2023).

 [5] S. Alwan, A. Sharoni &  Y.  Dubi, Role of Electrode Polarization in the Electron Transport Chirality-Induced Spin-Selectivity Effect, J. Phys. Chem. C 128, 15, 6438–6445 (2024).


 
4
Nov '24
In-person
+ Online
New York University
Javad Shabani
Probing Andreev Bound States in Superconductor-semiconductor Josephson Junctions
This talk is accessible via Zoom or use
meeting ID 829 2687 2594 and passcode 866995 to join
Abstract:
It is realized that by interfacing BCS superconductors and semiconductors with strong spin--orbit coupling it is possible to create a system that can host exotic states of matter. Hence epitaxial superconductors and semiconductors have emerged as an attractive materials system with atomically sharp interfaces and broad flexibility in device fabrications incorporating Josephson junctions.  We place our Al-InAs Josephson junction into circuit quantum electrodynamics to directly probe the Andreev bound states. We probe the microwave photons from a superconducting resonator that are coupled to the junction. These measurements reveal a coupling interaction between the resonator and the Andreev bound states, enabling the mapping of isolated individual Andreev bound states characterized by near-unity transparency and a substantial induced superconducting gap. Exploration of the gate parameter space illustrates the evolution of Andreev bound states with gate voltage, revealing the mapping of multiple Andreev bound states.
 
11
Nov '24
In-person
+ Online
Taiwan National University
Hsi-Sheng Goan
Accurate and Efficient Quantum Computations of Molecular Properties
This talk is accessible via Zoom or use
meeting ID 829 2687 2594 and passcode 866995 to join
20
Nov '24
University of Pennsylvania
Nader Enghta
TBA
9
Dec '24
In-person
+ Online
Queens College
Sarah Elghazoly
Terahertz-emitting high-temperature superconducting cuprate Bi2Sr2CaCu2O8+δ
This talk is accessible via Zoom or use
meeting ID 829 2687 2594 and passcode 866995 to join