Winning the Award of Excellence in theposter presentation in TSQS2024

Junhyeok Jeong, M2, Kondo Laboratory
The TSQS2024, or in other words, the International
Symposium on Quantum Electronics is an annualinternational workshop hosted by the Trans-Scale
Quantum Science Institute (TSQS). This workshop aims
to foster innovation by bridging a wide spectrum ofquantum science disciplines. This year, the symposium
was held from February 13 to 16 at the Ito International
Research Center at the University of Tokyo. This
program includes both an oral and a poster presentation
session, and each participant can give their talk in eitherway. The program committees evaluate how the poster
and the research are innovative and well-explained to
Figure 1. Me holding the award ofexcellence in the poster presentation.

other participants. And present an award to someselected participants.

The most studied cuprates so far are so-called ‘single
It was my first time joining the international workshop,

layer’ or ‘bilayer’ which means there is one or two CuO2

and also it was my first time presenting a poster toplanes where the superconductivity emerges imbeddedaudiences. Even though I was quite nervous until justbetween the dopant layers. However, my study aimed tobefore

could enjoy thethe ‘multilayered’ cuprate which has multiple (more thanatmosphere of the hall, the talk, and everything in there.

three) CuO2 layers inside one unit cell. This multilayer

Also, it is a great honor to be selected as one of the award

cuprate includes a ‘clean’ innermost CuO2 plane, whichwinners.

is well protected from the spatial inhomogeneity thatthepresentation

day, I

inevitably comes from the dopant layer by the otherQuantum Electronics, which seems to be a little vague

CuO2 planes (Figure 2. a). It means that the innermost

nomenclature, covers large research fields including

CuO2 plane remains structurally flat and electronicallytransport, magnetism, or even cosmologies. My researchhomogeneous hence it is suitable for studying thewas on the high-Tc superconductors. A superconductor isintrinsic physics of the cuprate.

an exotic material that shows zero resistivity under acritical temperature (Tc). This fascinating property can

The intriguing feature of the innermost clean CuO2 plane

be applied to ways, such as ultrahigh-efficiency electricistransport or Magnetic Resonance Imaging (MRI), so

antiferromagnetic order. It had been clearly revealed bytherehigh-Tc

the study of a five-layer system. However, the observed

superconductors and the copper-based superconductor

superconducting pairing gap in the five-layer system was(Cuprate) is one of the highest-Tc materials so far in therather small, an order of a few meV. Hence I focused thefield, but nobody knows how the high-Tc is achieved infour-layer system, which may possess a slightly

cuprate.

increased doping level than the five-layer system.

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havebeenhugeefforts

物性研だより第 64 巻第 2 号tofindthatthesuperconductivity

coexists■■ ■withthe■ ■ ■ ■The measured superconducting gap in the four-layer

The observed pairing strength in the four-layer systemsystem was around 15 meV to 30 meV within a very tiny

was indeed extremely large, around 0.69 at maximum.

doping level difference. This pairing gap is actually 3 toThis result suggests that the strong superconducting

6 times larger than that of the five-layer system,

pair exists in a clean- and underdoped inner plane andsuggesting that the superconducting pair can stay strong

will pave the way to investigate a high-Tc mechanism ofeven under the presence of the antiferromagnetic order.

cuprates.

Moreover, since the electronic band topology of the ‘small’Fermi pocket is quite different from the conventional

About this result, I want to thank all the co-authors of

single- and bilayer systems, it is possible to discuss about

the work. Without them, I would not be able to get a

the pairing strength, which is a physical parameterfruitful result and the award. Especially, I want to takeindicating how the superconducting pairs formed

a moment to express my sincere gratitude to Prof.

strongly (Figure 2. b, c).

Takeshi Kondo, as my academic supervisor, and also I
am very thankful to Dr. Soonsang Huh, Dr. Kifu

The pairing strength is calculated by the ratio of theKurokawa, and Mr. Yuyang Dong for the insightful

superconducting gap (Δ) and the Fermi energy (ε F).

discussion.

Figure 2. (a)The crystal structure of a four-layer system. The inner plane (IP) is wellprotected by the outer planes (OP), and hence remains clean and homogeneous. (b)Theelectronic band topology of IP, which shows a small pocket at a Fermi energy. The band top(or Fermi energy) is rather small, an order of few tens of meV. (c)Same with (b) but of OP.
This band topology was seen in many conventional cuprates.

■■■■ ■■■

物性研だより第 64 巻第 2 号

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