Quantum Condensed Phases Research Team

Principal Investigator

PI Name Kimitoshi Kono
Degree Ph.D.
Title Team Leader
Brief Resume
1982Ph.D., University of Tokyo
1982Research Associate, Hyogo University of Teacher Education
1987Associate Professor, Hyogo University of Teacher Education
1989Associate Professor, Institute of Physics, University of Tsukuba
1992Associate Professor, Institute for Solid State Physics, University of Tokyo
2000Chief Scientist, Low Temperature Physics Laboratory, RIKEN
2013Team Leader, Quantum Condensed Phases Research Team, Quantum Information Electronics Division, RIKEN Center for Emergent Matter Science (-present)
2018Chair Professor, International College of Semiconductor Technology, National Chiao Tung University (-present)


We will develop techniques to manipulate single electrons and ions trapped at an extremely clean surface of liquid helium, which will be utilized to fabricate quantum effect devices. This includes lateral confinement techniques and control of quantum transitions between discrete energy levels due to the abovementioned confinement and due to surface states, and atoms and ions imbedded in liquid helium.

Research Fields

Low Temperature Physics


Surface phenomena
Two-dimensional electron system
Quantum computing


Study of elementary excitation of superfluid helium with Dy atoms imbedded in liquid helium

Interaction between helium (He) atoms and metallic atoms and ions imbedded in liquid He results in various intriguing phenomena.  Laser spectroscopy of Dysprosium (Dy) atoms introduced in liquid He by laser ablation has been successfully carried out to elucidate the creation of a single elementary excitation of superfluid He, phonon and roton, for the first time.

Absorption spectra of Dy atoms revealed a clear signature of a sharp zero-phonon line (ZPL) and broad phonon-wing (PW) which is associated with the creation of a single elementary excitation of superfluid helium.  From the line-width of ZPL, we will know the rate of elastic scattering off thermally excited elementary excitations from Dy atomic bubble.

We successfully measured the temperature dependence of the ZPL width for the first time. The temperature dependence is qualitatively explained by a model taking into account the density of elementary excitations and scattering cross-section (Figure).

Dispersion diagram of superfluid He (black, right axis); calculated scattering cross section σ(k) (red, left axis) and the density of elementary excitations at T=1.5 K (blue, arb. units). Two horizontal dashed lines mark the calculated frequencies of the atomic bubble oscillation modes.


Kimitoshi Kono

Team Leader kkono[at]riken.jp R