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Publications

Quantum Oscillations in Graphene Using Surface Acoustic Wave Resonators

Cornell Affiliated Author(s)
Author
Yawen Fang
Yang Xu
Kaifei Kang
Benyamin Davaji
Kenji Watanabe
Takashi Taniguchi
Amit Lal
Kin Mak
Jie Shan
B. Ramshaw
Abstract

Surface acoustic waves (SAWs) provide a contactless method for measuring wave-vector-dependent conductivity. This technique has been used to discover emergent length scales in the fractional quantum Hall regime of traditional, semiconductor-based heterostructures. SAWs would appear to be an ideal match for van der Waals heterostructures, but the right combination of substrate and experimental geometry to allow access to the quantum transport regime has not yet been found.

Journal
Physical Review Letters
Date Published
Group (Lab)
Brad Ramshaw Group

Symmetry Control of Unconventional Spin–Orbit Torques in IrO2

Cornell Affiliated Author(s)
Author
Michael Patton
Gautam Gurung
Ding-Fu Shao
Gahee Noh
Joseph Mittelstaedt
Marcel Mazur
Jong-Woo Kim
Philip Ryan
Evgeny Tsymbal
Si-Young Choi
Daniel Ralph
Mark Rzchowski
Tianxiang Nan
Chang-Beom Eom
Abstract

Abstract Spin?orbit torques generated by a spin current are key to magnetic switching in spintronic applications. The polarization of the spin current dictates the direction of switching required for energy-efficient devices. Conventionally, the polarizations of these spin currents are restricted to be along a certain direction due to the symmetry of the material allowing only for efficient in-plane magnetic switching.

Journal
Advanced Materials
Date Published
Funding Source
ONR N00014-20-1-2844
DMR-1720415
GBMF9065
DE-FG02-06ER46327
DE-SC0017671
OIA-2044049
2020R1A4A1018935

Superconductivity, Charge Density Wave, and Supersolidity in Flat Bands with a Tunable Quantum Metric

Cornell Affiliated Author(s)
Author
J.S. Hofmann
E. Berg
D. Chowdhury
Abstract

Predicting the fate of an interacting system in the limit where the electronic bandwidth is quenched is often highly nontrivial. The complex interplay between interactions and quantum fluctuations driven by the band geometry can drive competition between various ground states, such as charge density wave order and superconductivity. In this work, we study an electronic model of topologically trivial flat bands with a continuously tunable Fubini-Study metric in the presence of on-site attraction and nearest-neighbor repulsion, using numerically exact quantum Monte Carlo simulations.

Journal
Physical Review Letters
Date Published
Group (Lab)
Debanjan Chowdhury Group

Transferring orbital angular momentum to an electron beam reveals toroidal and chiral order

Cornell Affiliated Author(s)
Author
K.X. Nguyen
Y. Jiang
M.C. Cao
P. Purohit
A.K. Yadav
P. García-Fernández
M.W. Tate
C.S. Chang
P. Aguado-Puente
J. Íñiguez
F. Gomez-Ortiz
S.M. Gruner
J. Junquera
L.W. Martin
R. Ramesh
D.A. Muller
Abstract

Orbital angular momentum (OAM) and torque transfer play central roles in a wide range of magnetic textures and devices including skyrmions and spin-torque electronics. Analogous topological structures are now also being explored in ferroelectrics, including polarization vortex arrays in ferroelectric/dielectric superlattices. Unlike magnetic toroidal order, electric toroidal order does not couple directly to linear external fields.

Journal
Physical Review B
Date Published
Funding Source
DMR-1719875
DE-SC0002334
DE-FG02-10ER46693
FA9550-16-1-0031
PGC2018-096955-B
C15/MS/10458889
Group (Lab)
Sol M. Gruner Group

A geometrical perspective on development

Cornell Affiliated Author(s)
Author
A. Raju
E.D. Siggia
Abstract

Cell fate decisions emerge as a consequence of a complex set of gene regulatory networks. Models of these networks are known to have more parameters than data can determine. Recent work, inspired by Waddington's metaphor of a landscape, has instead tried to understand the geometry of gene regulatory networks. Here, we describe recent results on the appropriate mathematical framework for constructing these landscapes. This allows the construction of minimally parameterized models consistent with cell behavior.

Journal
Development Growth and Differentiation
Date Published
Funding Source
2013131
Research Area

Interplay of hidden orbital order and superconductivity in CeCoIn5

Cornell Affiliated Author(s)
Author
W. Chen
Neerup Breiø
F. Massee
M.P. Allan
C. Petrovic
J.C.S. Davis
P.J. Hirschfeld
B.M. Andersen
A. Kreisel
Abstract

Visualizing atomic-orbital degrees of freedom is a frontier challenge in scanned microscopy. Some types of orbital order are virtually imperceptible to normal scattering techniques because they do not reduce the overall crystal lattice symmetry. A good example is dxz/dyz (π,π) orbital order in tetragonal lattices. For enhanced detectability, here we consider the quasiparticle scattering interference (QPI) signature of such (π,π) orbital order in both normal and superconducting phases.

Journal
Nature Communications
Date Published
Funding Source
DE-FG02-05ER46236
GBMF9457
DE-SC0012704
R64897
DLV-788932
SFI 17/RP/5445
Group (Lab)
J.C. Seamus Davis Group

Calorimetric measurement of nuclear spin-lattice relaxation rate in metals

Cornell Affiliated Author(s)
Author
A. Khansili
A. Bangura
R. McDonald
B. Ramshaw
A. Rydh
A. Shekhter
Abstract

The quasiparticle density of states in correlated and quantum-critical metals directly probes the effect of electronic correlations on the Fermi surface. Measurements of the nuclear spin-lattice relaxation rate provide one such experimental probe of quasiparticle mass through the electronic density of states. By far the most common way of accessing the spin-lattice relaxation rate is via nuclear magnetic resonance and nuclear quadrupole resonance experiments, which require resonant excitation of nuclear spin transitions.

Journal
Physical Review B
Date Published
Group (Lab)
Brad Ramshaw Group

Comparing study features is easy but identifying next steps is hard: Evaluating critical thinking through the Biology Lab Inventory of Critical Thinking in Ecology

Cornell Affiliated Author(s)
Author
Ashley Heim
David Esparza
N. Holmes
Michelle Smith
Abstract
Critical thinking, which can be defined as the evidence-based ways in which people decide what to trust and what to do, is an important competency included in many undergraduate science, technology, engineering, and mathematics (STEM) courses. To help instructors effectively measure critical thinking, we developed the Biology Lab Inventory of Critical Thinking in Ecology (Eco-BLIC), a freely available, closed-response assessment of undergraduate students critical thinking in ecology.
Journal
Ecology and Evolution
Date Published

Etoposide promotes DNA loop trapping and barrier formation by topoisomerase II

Cornell Affiliated Author(s)
Author
T.T. Le
M. Wu
J.H. Lee
N. Bhatt
J.T. Inman
J.M. Berger
M.D. Wang
Abstract

Etoposide is a broadly employed chemotherapeutic and eukaryotic topoisomerase II poison that stabilizes cleaved DNA intermediates to promote DNA breakage and cytotoxicity. How etoposide perturbs topoisomerase dynamics is not known. Here we investigated the action of etoposide on yeast topoisomerase II, human topoisomerase IIα and human topoisomerase IIβ using several sensitive single-molecule detection methods. Unexpectedly, we found that etoposide induces topoisomerase to trap DNA loops, compacting DNA and restructuring DNA topology.

Journal
Nature Chemical Biology
Date Published
Funding Source
R01-CA077373
R01GM136894
R35-CA263778
T32GM008267
Research Area
Group (Lab)
Michelle Wang Group

Graph gauge theory of mobile non-Abelian anyons in a qubit stabilizer code

Cornell Affiliated Author(s)
Author
Y.D. Lensky
K. Kechedzhi
I. Aleiner
Eun-Ah Kim
Abstract

Stabilizer codes allow for non-local encoding and processing of quantum information. Deformations of stabilizer surface codes introduce new and non-trivial geometry, in particular leading to emergence of long sought after objects known as projective Ising non-Abelian anyons. Braiding of such anyons is a key ingredient of topological quantum computation. We suggest a simple and systematic approach to construct effective unitary protocols for braiding, manipulation and readout of non-Abelian anyons and preparation of their entangled states.

Journal
Annals of Physics
Date Published
Funding Source
920665
OAC-2118310
PHY-160761
Group (Lab)