Educational and Working History

Research Interest

Electron transport and superconductivity in surface nanostructures

(see [1][9] in the publication list)

Self-assembled surface nanostructures have advantages such as extremely high crystallinity and well-defined atomic-scale morphology, compared to lithographically fabricated ones. These features provide opportunities for studying novel electron transport phenomena and for utilizing them as building blocks for future nano-electronics. He has been investigating electron transport through unique nanostructures such as monatomic metal layers self-assembled on clean silicon surfaces. He has successfully demonstrated the very existence of electron transport through 1D indium atomic chains, and has clarified their metal-insulator transition at low temperatures, a hallmark of a one-dimensional metallic system. He has also unambiguously found a robust superconducting transition of 2D monatomic indium layer on silicon by transport measurements, against the prevailing belief that ideal 2D system cannot be superconducting at finite temperatures. This newly found surface superconducting material can be the basis for many applications, e.g., realization of topological superconductors and decoherence-tolerant quantum computation.

Structurally modulated one-dimensional metal films

(see [2][4][5][7][8] in the publication list)

Fabrication of new form of low-dimensional materials is highly desirable for the development of nanotechnology. He has demonstrated that structurally modulated Ag films can be fabricated using an atomic-scale surface template. These Ag films, composed of atomically narrow stripes separated by periodically aligned stacking faults, are surprisingly stable. He has found that highly anisotropic quantum well states and one-dimensional surface states are formed and that 1D organic chains can be assembled along the stacking fault steps. These unique structures could be utilized for 1D spin information transport.

Magnetism and quantum phenomena in low dimensional systems

(see [3][6] in the publication list)

Observation and control of magnetic properties at atomic scale are fundamentally important in terms of further development of spintronics. He has succeeded in controlling the Kondo effect, a representative many-body quantum phenomenon of electron spins, of magnetic adatoms on metal surfaces using magnetic metal multilayers. The Kondo temperature has been modulated through the quantum well states formed in the multilayers in a layer-by-layer fashion. This opens the way to manipulate spins of individual atoms and molecules with tailored nanostructures. He has also found a method for realizing a high spin contrast imaging using a scanning tunneling microscope. This technique could be applied to realize spin-driven molecular motors.

List of important recent publications

1. Macroscopic Superconducting Current through a Silicon Surface Reconstruction with Indium Adatoms: Si(111)-(√7×√3)-In

   T. Uchihashi, P. Mishra, M. Aono, and T. Nakayama

   Phys. Rev. Lett. 107, 207001 (2011), highlighted as an Editor's Suggestion and a Viewpoint in Physics

2. One-dimensional surface states on a striped Ag thin film with stacking fault arrays

   T. Uchihashi, P. Mishra, K. Kobayashi, and T. Nakayama

   Phys. Rev. B 84, 195466 (2011)

3. Enhanced spin contrast of epitaxial Mn films on Fe(100) by spin-polarized scanning tunneling microscopy

   P. Mishra, T. Uchihashi, and T. Nakayama

   Appl. Phys. Lett. 98, 123106 (2011)

4. Strong Electron Confinement By Stacking-fault Induced Fractional Steps on Ag(111) Surfaces

   T. Uchihashi, K. Kobayashi, and T. Nakayama

   Phys. Rev. B 82, 113413 (2010)

5. Self-alignment of Co adatoms on In atomic wires by quasi-one-dimensional electron gas mediated interaction

   C. Liu, T. Uchihashi, and T. Nakayama

   Phys. Rev. Lett. 101, 146104 (2008)

6. Quantum modulation of the Kondo resonance of Co adatoms on Cu/Co/Cu(100): Low-temperature scanning tunneling spectroscopy study

   T. Uchihashi, J. Zhang, J. Kroger, and R. Berndt

   Phys. Rev. B 78, 033402 (2008)

7. Quasi-quantum-wire states in an epitaxial Ag film on a one-dimensional surface superstructure

   N. Nagamura, I. Matsuda, N. Miyata, T. Hirahara, S. Hasegawa, and T. Uchihashi

   Phys. Rev. Lett. 96, 256801 (2006)

8. Quantum modulation of the Kondo resonance of Co adatoms on Cu/Co/Cu(100): Low-temperature scanning tunneling spectroscopy study

   T. Uchihashi, C. Ohbuchi, S. Tsukamoto, and T. Nakayama

   Phys. Rev. B 78, 033402(2008)

9. Electron conduction through quasi-one-dimensional indium wires on silicon

   T. Uchihashi and U. Ramsperger

   Appl. Phys. Lett, 80. 4169-4171 (2002)

List of recent invited talks in international conferences

1. T. Uchihashi, "Atomically Thin Superconductors on Silicon Surfaces", The 6th International Workshop on Advanced Materials Science and Nanotechnology (IWAMSN 2012), Ha Long City, Vietnam, Oct. 30 ? Nov. 2, 2012.

2. T. Uchihashi, "Superconductivity at silicon surfaces with metal adatoms and molecules", 1st International Conference on Emerging Advanced Nanomaterials (ICEAN), Brisbane, Australia, Oct. 22-25, 2012.

3. T. Uchihashi, "Superconductivity at adatom/molecule-induced silicon surfaces and interfaces", The 13th Trends in Nanotechnology International Conference (TNT2012), Madrid, Spain, Sep. 10-14, 2012.

4. T. Uchihashi, "Macroscopic Supercurrent through a Metal-Induced Silicon Surface Reconstruction: Si(111)-(√7×√3)-In", Symposium on Surface and Nano Science 2012 (SSNS' 12), Shizukuishi, Japan, Jan. 9-12, 2012.

5. T. Uchihashi, Puneet Mishra, Masakazu Aono, and Tomonobu Nakayama, "Macroscopic Supercurrent through a Silicon Surface Reconstruction with Indium Adatoms Observed by Transport Measurements", International Symposium on Surface Science (ISSS-6), Tower Hall Funabori, Funabori, Tokyo, Japan, Dec. 11-15, 2011.

6. T. Uchihashi, "Stacking-fault Superlattices and One-dimensional Surface States of Epitaxial Ag Films on Silicon", 18th International Vacuum Congress (IVC18), Beijing International Conference Center, Beijing, Chiana, Aug. 22-28, 2010.

7. T. Uchihashi, "ONE-DIMENSIONAL SILVER THIN FILMS", NMS-V & FCFP-XIX & PS-III:International, Fudan University, Shanghai, China, Oct.18-22, 2009.