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"Essential
Ingredients for Superconductivity in Copper Oxide Superconductors"
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Date: |
Download-files: |
Time: |
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Thursday,
09 June 2022 |
Video-Recording for any system with MP4-support - Video.mp4 (ca. 424 Mb) |
15:15 – 16:30
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Zhi-Xun Shen
(Stanford University)
Abstract:
High-temperature superconductivity in
copper oxides, with critical temperature
well above what was anticipated by the BCS
theory, remains a major unsolved
physics problem. The problem is
fascinating because it is simultaneously simple
- being a single band and ½ spin system,
yet extremely rich - boasting d-wave
superconductivity, pseudogap, spin and
charge orders, and strange metal
phenomenology. For this reason, cuprates
symbolize the intellectual challenge
for correlated electrons – stimulating
conversations on the physics of Hubbard
model, quantum critical point, Planckian
metal, and influencing the discussions
from cold atoms to twist-stacked 2D
materials.
Central to this debate is whether the
Hubbard model, which is the natural
starting point for the undoped magnetic
insulator, contains the essential
ingredients for key physics in cuprates.
In this talk, I will discuss photoemission
evidence for a multifaceted answer to this
question [1-3], leading to the conclusion
that the Hubbard physics is necessary but
not sufficient to describe the rich physics.
First, we show results that naturally
points to the importance of Coulomb and
magnetic interactions, including d-wave
superconducting gap structure [4],
exchange energy (J) control of bandwidth
in single-hole dynamics [5].
Second, we evidence effects beyond the
Hubbard model, including band dispersion
anomalies at known phonon frequencies [6,
7], polaronic spectral lineshape and
the emergence of quasiparticle with doping
[8].
Third, we show properties likely of hybrid
electronic and phononic origin,
including two energy scales for pseudogap
(defined as gaps above Tc), and
the almost vertical phase boundary near
the critical 19% doping [9-12].
Fourth, we illustrate examples of small q
phononic coupling that cooperates with
d-wave superconductivity [13-15]. The
additional phononic involvement is
consistent with the recent experimental
advance in synthesizing and investigating
doped one-dimensional (1D) cuprates [16],
where a more reliable 1D calculation
enables a robust comparison.
Finally, we discuss the physics of strong
phase fluctuations in cuprates [17-18].
These observations allow us to connect the
dots of the above classes of
experimental observables and provide a
holistic picture of the essential
microscopic ingredients for cuprates
physics, including the elusive d-wave
superconductivity in 2D Hubbard model.
[1] A. Damascelli, Z. Hussain, and Z.-X.
Shen, Review of Modern Physics, 75, 473 (2003)
[2] M. Hashimoto et al., Nature Physics
10, 483 (2014)
[3] JA Sobota, Y He, ZX Shen; Rev. of Mod.
Phys. 93, 025006 (2021)
[4] Z.-X. Shen et al., Phys. Rev. Lett. 70, 1553 (1993)
[5] B.O. Wells et
al., Phys. Rev. Lett. 74, 964 (1995)
[6] A. Lanzara et
al., Nature 412, 510 (2001)
[7] T. Cuk et al., Phys. Rev. Lett., 93, 117003 (2004)
[8] K.M. Shen et al.,
Phys. Rev. Lett., 93, 267002 (2004)
[9] D.M. King et al., J. of Phys. &
Chem of Solids 56, 1865 (1995)
[10] D.S. Marshall et al., Phy. Rev. Lett.
76, 484 (1996)
[11] A.G. Loeser et al., Science 273, 325
(1996)
[12] S.D. Chen et al., Science, 366, 6469
(2019)
[13] T.P. Devereaux, T. Cuk, Z.X. Shen, N.
Nagaosa, Phys. Rev. Lett., 93,
117004 (2004)
[14] S. Johnston et
al., Phys. Rev. Lett. 108, 166404 (2012)
[15] Yu He et al., Science, 362, 62 (Oct.
2018)
[16] Z. Chen, Y. Wang et al., Sciecne 373,
1235 (2021)
[17] S.D. Chen et al., Nature 601, 562-567
(2022)
[18] Yu He et al. Phys. Rev. X 11, 031068
(2021)
Biography: Zhi-Xun Shen is a member of the
US National Academy of Sciences,
the American Academy of Arts and Sciences,
and the Chinese Academy of Sciences.
His primary interest is novel quantum
phenomena in materials. His work has been
recognized by the E.O. Lawrence Award, the
Oliver E. Buckley Prize,
the H. Kamerlingh Onnes Prize, the
Einstein Professorship Award of CAS,
and the Tage Erlander professorship of the
Swedish Research Council.
He has been Chief Scientist of SLAC and
director of the Institute for Material and
Energy Sciences and of the Geballe Laboratory
for Advanced Materials at
Stanford University. He has mentored close
to one hundred graduate students and
post-docs and he is a co-inventor of
several patents.