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"Essential Ingredients for Superconductivity in Copper Oxide Superconductors"

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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

 

 

                                                     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.

 

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