NYU Arts & Science
Condensed Matter Physics Seminars
May 24, 2018 Thursday 10:00 AM  +
726 Broadway, room 871
Soft Condensed Matter Seminars (csmr)

Dan Nguyen
UC Santa Barbara

Towards artificial chromatin: In vitro transcription with DNA liquids

DNA organization within a cell is multifaceted & dynamic, and has received intense study in recent decades. As a more complete understanding of chromatin organization emerges, there are increasing efforts to examine how such organization, and dynamic re-organization, relates to gene expression. While disruptions in chromatin organization have been shown to induce changes in transcriptional output, transcriptional activity has also been observed to trigger nuclear repositioning. It thus remains unclear which biological process drives the other or, more likely, if the interplay is much more intricate. To begin probing this incredibly complex relationship, we use a simple in vitro platform – comprised of self-assembling DNA nanostars (NSs) – to examine transcription from genes integrated into higher order nucleic acid complexes. These NSs can be tuned to adopt distinct phases, either a solid-like percolated network or a phase-separated liquid, depending on the strength of inter-NS interactions. With increasing reports describing the liquid-like behavior of chromatin, including the liquid-liquid phase separation exhibited by the nucleolus and heterochromatin domains, we implement the DNA-liquid phase into a cell-free gene expression system to examine how the integration of genes into a biomolecular liquid affects transcriptional output and, inversely, how transcribed RNA may alter that environment.

June 6, 2018 Wednesday 2:00 PM  +
726 Broadway, Room 1067, CQP Conference Room
Condensed Matter Physics Seminars (cmp)

Mingzhong Wu
Colorado State University

Nontrivial Nature and Penetration Depth of Topological Surface States in SmB6 Thin Films

Being the first rare earth mixed valence system and the first Kondo insulator, SmB6 may very likely be the first topological Kondo insulator too. Recent studies have confirmed the existence of topological surface states (TSS) and surface chiral spin textures in single-crystal SmB6 bulk materials, but the nontrivial nature and depth scale of the TSS remain unresolved. In this talk I will report our recent work on the use of spin pumping to study the nontrivial feature of the TSS in SmB6. Our experiments used SmB6 thin films grown on magnetic insulator Y3Fe5O12 (YIG) bulk materials. Upon the excitation of magnetization precession in the YIG, a pure spin current is generated that flows from the YIG into the SmB6 film and produces, via spin-orbit coupling, a lateral electrical voltage in the SmB6 film. The spin-pumping voltage signal becomes considerably stronger as the temperature decreases from 150 K to 10 K. Such an enhancement most likely originates from the spin-momentum locking feature of the TSS of the SmB6 film and may thereby serve as a strong evidence for the nontrivial nature of the TSS. The voltage data also show a unique film thickness dependence that suggests a TSS depth of about 32 nm for the TSS. The data also indicate a spin diffusion length of about 39 nm in the SmB6 film. The spin-pumping results are supported by temperature-dependent transport measurements and theoretical analyses using a tight binding model.

June 21, 2018 Thursday 11:00 AM  +
726 Broadway, Room 1067
Condensed Matter Physics Seminars (cmp)

Eric Lutz
University of Stuttgart

Irreversibility and the quantum arrow of time

Irreversibility is one of the most intriguing concepts in physics. While microscopic physical laws are perfectly reversible, macroscopic average behavior has a preferred direction in time. According to the second law of thermodynamics, this arrow of time is associated with a positive mean entropy production. We will discuss the physics of the quantum arrow of time and present results of recent experimental investigations of irreversibility in a nuclear magnetic resonance setup.

September 12, 2018 Wednesday 3:00 PM  +
726 Broadway, room 871
Soft Condensed Matter Seminars (csmr)

David Saintillan


September 18, 2018 Tuesday 11:00 AM  +
726 Broadway Room 1067
Condensed Matter Physics Seminars (cmp)

Jennifer Cano
Princeton University