Theoretical study of electron orbital motion

2022 Fiscal Year Final Research Report

• Project/Area Number: 17K14333
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Condensed matter physics II
• Research Institution: Hiroshima University (2021-2022); The University of Tokyo (2017-2020)
• Principal Investigator: Tada Yasuhiro 広島大学, 先進理工系科学研究科(先), 准教授 (20609937)
• Project Period (FY): 2017-04-01 – 2023-03-31
• Keywords: 軌道角運動量 / 軌道効果 / 磁場 / 量子臨界現象 / カイラル超流動体 / Diracフェルミオン

Outline of Final Research Achievements

We have theoretically studied quantum effects of electrons' spatial motion in a system. Concrete subjects include "orbital effects in superfluids and superconductors", "quantum criticality in Dirac systems under magnetic fields", "orbital effects by an optical vortex", "approximate magnetic translation".
First, we discussed the orbital angular moment paradox in chiral superfluids. Especially, we pointed out that the angular moment is not a thermodynamic quantity and therefore it causes a paradox. This very elementary property has been missed in the long history of this problem. Also, this implies that one should carefully think whether or not the longstanding paradox is a well-defined problem which has a definite answer.
We also studied interacting Dirac systems under magnetic fields especially focusing on the quantum critical phenomena. We performed numerical calculations and clarified their behaviors near a quantum critical point and discussed the so-called magnetic catalysis.

Free Research Field

量子多体系の理論

Academic Significance and Societal Importance of the Research Achievements

カイラル超流動体の軌道角運動量パラドックスについては、それまで40年間の研究の歴史の中で、そもそも軌道角運動量の値が何かしら定まっており、問題はその値を明らかにすることであると考えられてきた。研究代表者が示したことは、そもそも軌道角運動量はバルクに定まった値をもたず、表面条件などの普段は無視してしまう条件に非常に敏感に依存する、ということである。これはこの問題を根本から問い直すものであり、問題の解決に向けた重要な一歩であるということができる。