I am a theoretical physicist.
My job is to create new physical theories and write papers.
Why write a thesis? There are many practical reasons, like promotion, recognition, and fame, but the most fundamental reason is that I have a unique story to share with others.
But the others I'm talking about here are other researchers working in the same field as me.
The target has to be narrow.
Even if I look around the world, there are only about twenty people who would read and be interested in the thesis I poured all my effort into completing over the past six months.
Considering the motivation alone, writing a book for the public is no different from writing a thesis.
When you have your own story, when you feel like sharing it with friends and colleagues in private or on social media is not enough, when you have a story that makes you feel like you're ready to die telling it, then a type of person called a "writer" is born.
I also have a story I want to leave behind before I take another step forward in life.
It's a story about material.

--- p.11

This book contains no narratives about the vast universe or the world of elementary particles that challenge the realm of God.
The starting point of the book is atoms, the root and framework of everyday life, and quantum mechanics, which explains atoms.
This book starts from the atom and grows in size.
Going out into the material world.
Rather than familiar substances commonly found in everyday life, it mainly deals with the world of unique substances that can only be found in laboratories.
The world of true quantum matter is similar to the world of martial arts masters who live in seclusion in the mountains and devote themselves solely to practicing martial arts.
I don't come out of the lab very often.
I would like to share the story of a major sect that dominates the martial arts world.
The classes of quantum materials covered in this book include superconductors, superfluids, quantum Hall materials, graphene, Dirac materials, and topological materials.
It may sound a little strange, but light is also matter.

--- p.13

The act of science can be likened to tying a brilliant hypothesis to a string and hanging it from the ceiling, and then having scientists in the kitchen below conduct various experiments and calculations to verify the hypothesis's validity.
If the hypothesis turns out to be correct, the line will be lowered, and anyone working in the kitchen will be able to touch and smell the hypothesis.
The hypothesis is now called a 'doctrine' or a 'law'.
Thanks to someone hanging that lump of hypothetical stuff from the ceiling a long time ago, I can finally get to work in the kitchen.
Democritus is the one who hung the very attractive hypothesis called 'atoms' from the ceiling, and scientists have been busy working in the kitchen for over two thousand years to bring his hypothesis down to the kitchen, to the orthodoxy, to the world of truth.

--- pp.23~24

“If we set aside the claim that there is something that cannot be divided any further, the answers of Empedocles, Democritus, and Plato are fundamentally correct.
Although the 'answers' the Greeks gave were inaccurate the more you looked into them, the 'questions' they asked were very precise scientific questions.
Modern science has filled in the gaps in the answers they offered, using rigorous mathematical language instead of vague language.

“I think the thousands of years since Plato have been spent developing the scientific tools and mathematical language needed to fill in these gaps.”
--- pp.36~37

The saddest moment for a scientist is not when his work fails, but when it is meaningless.
Although the conclusion alone suggests that the theory was a failure, historically speaking, the Timaeus contains gem-like elements that could be considered the first book to contain a theory of matter.
In particular, I would like to point out that the most attractive aspect is that the results of rigorous mathematical proofs were applied to the interpretation of natural phenomena.
Since Timaeus, there have been 25 centuries of exploration into the nature of matter.
To sum up the conclusion in one word:
'All matter is quantum matter.'
--- p.45

There is a hotel.
The name is Pauli Hotel.
This hotel has one unique, unbreakable rule.
The rule is that only one man and one woman can enter each room.
There are empty rooms, rooms for men alone, rooms for women alone, and rooms for couples, but two men and two women are never allowed in the same room.
What hotel in the world would require such a strange rule, and for what reason?
--- p.78

The Pauli Hotel is the very substance.
Matter is made up of atoms, each of which consists of a nucleus containing protons and neutrons, and electrons orbiting around it.
Ultimately, all matter contains a number of electrons proportional to the number of atoms that make up that matter.
Each electron is housed in a room with a unique room number.
In quantum mechanics, this room number is called a quantum number.
All the matter we see around us is a kind of Pauli Hotel.

--- p.81

The subject Heisenberg presented to his fledgling student was neither the problem of the atomic world nor the problem of the universe.
The two questions he addressed were, “Why is a magnet a magnet?” and “Why does electricity flow in metal?”
At a time when the wonderful tool of quantum mechanics had just been born, and every capable theoretical physicist in Europe was eager to reap its benefits, why did Heisenberg bother with such a childish problem and ask his students to solve it?
--- p.101

It is highly unlikely that Onus achieved anything that could be called scientific achievement during those 26 years.
All he did was design the equipment to create the world's best low-temperature refrigerators, refine the designs, and train skilled workers to build and maintain the equipment.
While we should certainly be wary of romanticizing or heroizing the lives and achievements of scientists too much, it's impossible not to feel a twinge of emotion at this point.
How did he manage to endure 26 years without a single paper to brag about? Imagine Onnes's tenacity, the understanding and support of those around him, and the steady support of the Netherlands and Leiden University, a nation that supported his lab's work. A mixture of surprise, envy, and respect.

--- p.114

From Maxwell's proof that light is a wave to Schrödinger's creation of quantum mechanics equations, if we look at the beginning and end of the exploration, it is clear that the changes were like the creation of a new world.
But if we examine the process step by step, we can clearly see the gradual change, just as an acorn falls to the ground, sprouts, grows, and eventually becomes an oak tree.
In Planck's paper, which introduced the core constants of quantum mechanics, the word "quantum" did not appear even once, and in Einstein's paper, which argued that light was a particle, the word "photon" did not appear.
Instead, 'quantum' is being used freely.
The first person to officially use the term 'photon' was Gilbert Lewis (1875-1946), an American physical chemist, in 1926.
The phenomenon of concepts that were considered very cautious by (academic) seniors becoming naturally accepted by the next generation and cautiously moving on to the next step based on this is a consistent pattern of science, then and now.

--- p.166

We often think of material things as objects that we can see, touch, and feel directly.
There is a prejudice that matter must be a three-dimensional object with width, length, and height.
Modern material science overcame this bias (based on everyday experience) in the latter half of the 20th century.
There are two-dimensional and one-dimensional materials.

--- p.211

The word "magnet" usually evokes images much closer to "children's toys" than ones of wonder and awe.
I used to think that way too, until I became a physicist studying quantum materials.
In fact, magnets are mysterious substances that can only be understood if you properly understand the nature of quantum mechanics.

--- p.234