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Publications

Detection of a pair density wave state in UTe2

Cornell Affiliated Author(s)
Author
Q. Gu
J.P. Carroll
S. Wang
S. Ran
C. Broyles
H. Siddiquee
N.P. Butch
S.R. Saha
J. Paglione
J.C.S. Davis
X. Liu
Abstract

Spin-triplet topological superconductors should exhibit many unprecedented electronic properties, including fractionalized electronic states relevant to quantum information processing. Although UTe2 may embody such bulk topological superconductivity1–11, its superconductive order parameter Δ(k) remains unknown12. Many diverse forms for Δ(k) are physically possible12 in such heavy fermion materials13.

Journal
Nature
Date Published
Funding Source
DE-SC-0019154
GBMF9071
GBMF9457
R64897
DLV-788932
SFI 17/RP/5445
Group (Lab)
J.C. Seamus Davis Group

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

Visualizing the atomic-scale origin of metallic behavior in Kondo insulators

Cornell Affiliated Author(s)
Author
H. Pirie
E. Mascot
C.E. Matt
Y. Liu
P. Chen
M.H. Hamidian
S. Saha
X. Wang
J. Paglione
G. Luke
D. Goldhaber-Gordon
C.F. Hirjibehedin
J.C.S. Davis
D.K. Morr
J.E. Hoffman
Abstract

A Kondo lattice is often electrically insulating at low temperatures. However, several recent experiments have detected signatures of bulk metallicity within this Kondo insulating phase. In this study, we visualized the real-space charge landscape within a Kondo lattice with atomic resolution using a scanning tunneling microscope.

Journal
Science
Date Published
Group (Lab)
J.C. Seamus Davis Group

On the electron pairing mechanism of copper-oxide high temperature superconductivity

Cornell Affiliated Author(s)
Author
S.M. O’Mahony
W. Ren
W. Chen
Y.X. Chong
X. Liu
H. Eisaki
S. Uchida
M.H. Hamidian
J.C.S. Davis
Abstract

The elementary CuO2 plane sustaining cuprate high-temperature superconductivity occurs typically at the base of a periodic array of edge-sharing CuO5 pyramids. Virtual transitions of electrons between adjacent planar Cu and O atoms, occurring at a rate t/̄h and across the charge-transfer energy gap ℇ, generate “superexchange†spin–spin interactions of energy J ≈ 4t4=ℇ3 in an antiferromagnetic correlated-insulator state. However, hole doping this CuO2 plane converts this into a very-high-temperature superconducting state whose electron pairing is exceptional.

Journal
Proceedings of the National Academy of Sciences of the United States of America
Date Published
Group (Lab)
J.C. Seamus Davis Group

In-situ angle-resolved photoemission spectroscopy of copper-oxide thin films synthesized by molecular beam epitaxy

Cornell Affiliated Author(s)
Author
C.K. Kim
I.K. Drozdov
K. Fujita
J.C.S. Davis
I. Božović
T. Valla
Abstract

Angle-resolved photoemission spectroscopy (ARPES) is the key momentum-resolved technique for direct probing of the electronic structure of a material. However, since it is highly surface-sensitive, it has been applied to a relatively small set of complex oxides that can be easily cleaved in ultra-high vacuum. Here we describe a new multi-module system at Brookhaven National Laboratory (BNL) in which an oxide molecular beam epitaxy (OMBE) is interconnected with an ARPES and a spectroscopic-imaging scanning tunneling microscopy (SI-STM) module.

Journal
Journal of Electron Spectroscopy and Related Phenomena
Date Published
Group (Lab)
J.C. Seamus Davis Group

Atomic-scale visualization of electronic fluid flow

Cornell Affiliated Author(s)
Author
X. Liu
Y.X. Chong
R. Sharma
J.C.S. Davis
Abstract

The most essential characteristic of any fluid is the velocity field, and this is particularly true for macroscopic quantum fluids1. Although rapid advances2–7 have occurred in quantum fluid velocity field imaging8, the velocity field of a charged superfluid—a superconductor—has never been visualized. Here we use superconducting-tip scanning tunnelling microscopy9–11 to image the electron-pair density and velocity fields of the flowing electron-pair fluid in superconducting NbSe2.

Journal
Nature Materials
Date Published
Group (Lab)
J.C. Seamus Davis Group

Scattering interference signature of a pair density wave state in the cuprate pseudogap phase

Cornell Affiliated Author(s)
Author
S. Wang
P. Choubey
Y.X. Chong
W. Chen
W. Ren
H. Eisaki
S. Uchida
P.J. Hirschfeld
J.C.S. Davis
Abstract

An unidentified quantum fluid designated the pseudogap (PG) phase is produced by electron-density depletion in the CuO2 antiferromagnetic insulator. Current theories suggest that the PG phase may be a pair density wave (PDW) state characterized by a spatially modulating density of electron pairs. Such a state should exhibit a periodically modulating energy gap Δ P(r) in real-space, and a characteristic quasiparticle scattering interference (QPI) signature Λ P(q) in wavevector space.

Journal
Nature Communications
Date Published
Group (Lab)
J.C. Seamus Davis Group

Discovery of a Cooper-pair density wave state in a transition-metal dichalcogenide

Cornell Affiliated Author(s)
Author
X. Liu
Y.X. Chong
R. Sharma
J.C.S. Davis
Abstract

Pair density wave (PDW) states are defined by a spatially modulating superconductive order parameter. To search for such states in transition-metal dichalcogenides (TMDs), we used high-speed atomicresolution scanned Josephson-tunneling microscopy. We detected a PDW state whose electron-pair density and energy gap modulate spatially at the wave vectors of the preexisting charge density wave (CDW) state.

Journal
Science
Date Published
Group (Lab)
J.C. Seamus Davis Group

Severe Dirac Mass Gap Suppression in Sb2Te3-Based Quantum Anomalous Hall Materials

Cornell Affiliated Author(s)
Author
Y.X. Chong
X. Liu
R. Sharma
A. Kostin
G. Gu
K. Fujita
J.C.S. Davis
P.O. Sprau
Abstract

The quantum anomalous Hall (QAH) effect appears in ferromagnetic topological insulators (FMTIs) when a Dirac mass gap opens in the spectrum of the topological surface states (SSs). Unaccountably, although the mean mass gap can exceed 28 meV (or 320 K), the QAH effect is frequently only detectable at temperatures below 1 K. Using atomic-resolution Landau level spectroscopic imaging, we compare the electronic structure of the archetypal FMTI Cr0.08(Bi0.1Sb0.9)1.92Te3to that of its nonmagnetic parent (Bi0.1Sb0.9)2Te3, to explore the cause.

Journal
Nano Letters
Date Published
Group (Lab)
J.C. Seamus Davis Group

Atomic-scale electronic structure of the cuprate pair density wave state coexisting with superconductivity

Cornell Affiliated Author(s)
Author
P. Choubey
S.H. Joo
K. Fujita
Z. Du
S.D. Edkins
M.H. Hamidian
H. Eisaki
S. Uchida
A.P. Mackenzie
J. Lee
J.C.S. Davis
P.J. Hirschfeld
Abstract

The defining characteristic of hole-doped cuprates is d-wave high temperature superconductivity. However, intense theoretical interest is now focused on whether a pair density wave state (PDW) could coexist with cuprate superconductivity [D. F. Agterberg et al., Annu. Rev. Condens. Matter Phys. 11, 231 (2020)]. Here, we use a strong-coupling mean-field theory of cuprates, to model the atomic-scale electronic structure of an eight-unit-cell periodic, d-symmetry form factor, pair density wave (PDW) state coexisting with d-wave superconductivity (DSC).

Journal
Proceedings of the National Academy of Sciences of the United States of America
Date Published
Group (Lab)
J.C. Seamus Davis Group