Chiral excitonic instability of two-dimensional tilted Dirac cones
The Coulomb interaction among massless chiral particles harbors unusual emergent phenomena in solids beyond the conventional realm of correlated electron physics. An example of such an effect is excitonic condensation of interacting massless Dirac fermions, which drives spontaneous mass acquisition...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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American Physical Society
2020-09-01
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| Series: | Physical Review Research |
| Online Access: | http://doi.org/10.1103/PhysRevResearch.2.033479 |
| _version_ | 1827285965438189568 |
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| author | Daigo Ohki Michihiro Hirata Takehiro Tani Kazushi Kanoda Akito Kobayashi |
| author_facet | Daigo Ohki Michihiro Hirata Takehiro Tani Kazushi Kanoda Akito Kobayashi |
| author_sort | Daigo Ohki |
| collection | DOAJ |
| description | The Coulomb interaction among massless chiral particles harbors unusual emergent phenomena in solids beyond the conventional realm of correlated electron physics. An example of such an effect is excitonic condensation of interacting massless Dirac fermions, which drives spontaneous mass acquisition and whose exact nature remains actively debated. Its precursor fluctuations growing prior to the condensate have been suggested by a recent nuclear magnetic resonance study in an organic material, hosting a pair of two-dimensional (2D) tilted Dirac cones at charge neutrality. Here, we theoretically study the excitonic transition in 2D tilted cones to understand the electron-hole pairing instability as functions of temperature (T), chemical potential (μ), and in-plane magnetic field (H). By solving a gap equation within a weak-coupling treatment and incorporating self-energy effects due to the Coulomb interaction through a renormalization-group technique, we calculate excitonic instability in a T-μ-H parameter space, and find that the pairing is promoted as H is increased but suppressed as μ moves away from the charge-neutrality point. We show that these findings are explained by enhanced or degraded Fermi-surface nesting between the Zeeman-induced pockets connecting the two tilted cones. Furthermore, to evaluate the precursor excitonic fluctuations in relation to this diagram, we consider the Coulomb interaction via a ladder-type approximation and calculate the nuclear spin-lattice relaxation rate, which provides rational ways to understand otherwise puzzling experimental results in the organic material by the μ and H dependence of the instability. |
| first_indexed | 2024-04-24T10:23:32Z |
| format | Article |
| id | doaj.art-29bbe850f2c942ea984b9523a97461b0 |
| institution | Directory Open Access Journal |
| issn | 2643-1564 |
| language | English |
| last_indexed | 2024-04-24T10:23:32Z |
| publishDate | 2020-09-01 |
| publisher | American Physical Society |
| record_format | Article |
| series | Physical Review Research |
| spelling | doaj.art-29bbe850f2c942ea984b9523a97461b02024-04-12T17:01:12ZengAmerican Physical SocietyPhysical Review Research2643-15642020-09-012303347910.1103/PhysRevResearch.2.033479Chiral excitonic instability of two-dimensional tilted Dirac conesDaigo OhkiMichihiro HirataTakehiro TaniKazushi KanodaAkito KobayashiThe Coulomb interaction among massless chiral particles harbors unusual emergent phenomena in solids beyond the conventional realm of correlated electron physics. An example of such an effect is excitonic condensation of interacting massless Dirac fermions, which drives spontaneous mass acquisition and whose exact nature remains actively debated. Its precursor fluctuations growing prior to the condensate have been suggested by a recent nuclear magnetic resonance study in an organic material, hosting a pair of two-dimensional (2D) tilted Dirac cones at charge neutrality. Here, we theoretically study the excitonic transition in 2D tilted cones to understand the electron-hole pairing instability as functions of temperature (T), chemical potential (μ), and in-plane magnetic field (H). By solving a gap equation within a weak-coupling treatment and incorporating self-energy effects due to the Coulomb interaction through a renormalization-group technique, we calculate excitonic instability in a T-μ-H parameter space, and find that the pairing is promoted as H is increased but suppressed as μ moves away from the charge-neutrality point. We show that these findings are explained by enhanced or degraded Fermi-surface nesting between the Zeeman-induced pockets connecting the two tilted cones. Furthermore, to evaluate the precursor excitonic fluctuations in relation to this diagram, we consider the Coulomb interaction via a ladder-type approximation and calculate the nuclear spin-lattice relaxation rate, which provides rational ways to understand otherwise puzzling experimental results in the organic material by the μ and H dependence of the instability.http://doi.org/10.1103/PhysRevResearch.2.033479 |
| spellingShingle | Daigo Ohki Michihiro Hirata Takehiro Tani Kazushi Kanoda Akito Kobayashi Chiral excitonic instability of two-dimensional tilted Dirac cones Physical Review Research |
| title | Chiral excitonic instability of two-dimensional tilted Dirac cones |
| title_full | Chiral excitonic instability of two-dimensional tilted Dirac cones |
| title_fullStr | Chiral excitonic instability of two-dimensional tilted Dirac cones |
| title_full_unstemmed | Chiral excitonic instability of two-dimensional tilted Dirac cones |
| title_short | Chiral excitonic instability of two-dimensional tilted Dirac cones |
| title_sort | chiral excitonic instability of two dimensional tilted dirac cones |
| url | http://doi.org/10.1103/PhysRevResearch.2.033479 |
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