Mesoscopic Physics

Mesoscopic physics deals with things larger than micro, but smaller than macro, treating length scales of nm~μm. There, the system is small enough for quantum effects to play a key role, while it is large enough for us to have full control and engineering

On top of this arena, we study a wide range of exciting quantum physics in condensed matter, including the topics below.

Anyon and Fractional Statistics

In low-dimension, there is no prior reason for the identical particles to be fermion or boson. Instead, the exchange of the particles can induce an arbitrary phase to the wavefunction or even can transform a state to the other. These exotic quasi-particles are called anyons and can appear in strongly interacting low-dimensional condensed matter system, usually within electron fractionalization.  They can possibly be used as a topological quantum computing.

In our laboratory, we ask the following questions

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Topological Superconductor and Majorana Fermion

Topological superconductor(TSC) is the superconductor which has topological property in its band structure of Bogoliubov quasi particles.  The result of topological nature of this system is the emergence of Majorana Fermion at the boundary or vortex. Since an adiabatic exchange of Majoranas leads to the change of quantum ground state, it is called non-Abelian anyon. 

 Detecting the Majorana or TSC has been hot issue, because it is expected to be a platform for fault-tolerant quantum computation due to its robustness against non-topological defects.

 In this laboratory, we suggest and study a mesoscopic set-up (such as topological Josephson junction) which can give peculiar transport signature originated from Majorana fermion and topological superconductivity. 

See also,

Quantum Pump

Quantum pump is a device that generate a DC current without DC bias. For certain condition, one can emit single-electrons periodically. It leads to a quantized current and it is applicable for fundamental standard of electrical current. These devices also be used as a fundamental building block of Fermionic quantum optics, which reveals quantum nature of electrons such as indistinguishability.

In our laboratory, we study generation and manipulation of few-electrons and find a way to measure quantum nature of emitted electrons.

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Kondo Effect and Kondo Cloud

When a magnetic impurity exists in a metal, conduction electrons form a spin cloud that screens the impurity spin. This basic phenomenon is called the Kondo effect. Contrary to electric charge screening, the spin screening cloud occurs quantum coherently, forming spin-singlet entanglement with the impurity. Although the spins interact locally around the impurity, the Kondo screening cloud can spread out over micrometers.

In our laboratory, we study the Kondo effect and the Kondo cloud to understand

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Entanglement and Correlation on Quantum Dots

Quantum dot is a device confining electrons in a tiny region. Quantum dot can function as an artificial atom with high tunability of size, energy level, charge, spin, and etc. These properties of quantum dot allow to study strong correlation and entanglement in a controlled manner.

In our laboratory, we study

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Research Highlights History


Non-Abelian anyon collider

Time-domain braiding of anyons

Time-resolved Coulomb collision of electrons

Entanglement shells of multichannel Kondo clouds


Electron tunneling assisted Majorana Braiding

Fractional Statistics on Integer Quantum Hall Edges

Quantum Point Contact on Graphene

Universal Thermal Entanglement of Multichannel Kondo Effects


Detecting Kondo Entanglement

Negative Excess Shot Noise by Anyon Braiding

Picosecond Coherent Electron Motion

Observation of the Kondo Cloud


Ultrafast Emission of Single Electron

Topological Vacuum Bubble

Rydberg Atom Quantum Simulator

Nonlocal Thermal Entanglement of Majorana Fermions