Spontaneous spin superconductor state in ABCA-stacked tetralayer graphene

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Auteurs principaux:	Li, Shuai, Ren, Yuan-Hang, Li, Ao-Long, Jiang, Hua
Format:	Preprint
Publié:	2024
Sujets:	Mesoscale and Nanoscale Physics
Accès en ligne:	Acceder al recurso
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author	Li, Shuai Ren, Yuan-Hang Li, Ao-Long Jiang, Hua
author_facet	Li, Shuai Ren, Yuan-Hang Li, Ao-Long Jiang, Hua
contents	We theoretically demonstrate a spontaneous spin superconductor (SC) state in ABCA-stacked tetralayer graphene, under sequential effects of electron-electron (e-e) and electron-hole (e-h) interactions. First of all, we examine the ferromagnetic (FM) exchange instability and phase diagram of the system induced by the long-range e-e interaction. At non- or low-doping levels, the interaction trends to stabilize a FM phase with the coexisting electron and hole carriers. Superior to bilayer and trilayer systems, tetralayer graphene has a larger FM phase region and spin splitting, making it more advantageous to realize the spin SC state. Subsequently, we prove that the FM phase becomes unstable when attractive e-h interaction is considered. As a consequence, the spin SC state can be spontaneously formed at low temperature, where spin-triplet exciton pairs act as the equivalent of Cooper pairs. We further develop a consistent BCS-type theory for the spin SC state in ABCA-stacked graphene. The predicted spin superconducting gap can reach about $7.0$ meV, with a critical temperature of about 45 K for non-doping system. At last, we demonstrated a spin-current Josephson effect in the ABCA-stacked graphene spin SC heterojunction. Our findings enrich the prospective spin SC candidate materials, illuminating more possibilities for achieving non-dissipative super-spintronics.
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publishDate	2024
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spellingShingle	Spontaneous spin superconductor state in ABCA-stacked tetralayer graphene Li, Shuai Ren, Yuan-Hang Li, Ao-Long Jiang, Hua Mesoscale and Nanoscale Physics We theoretically demonstrate a spontaneous spin superconductor (SC) state in ABCA-stacked tetralayer graphene, under sequential effects of electron-electron (e-e) and electron-hole (e-h) interactions. First of all, we examine the ferromagnetic (FM) exchange instability and phase diagram of the system induced by the long-range e-e interaction. At non- or low-doping levels, the interaction trends to stabilize a FM phase with the coexisting electron and hole carriers. Superior to bilayer and trilayer systems, tetralayer graphene has a larger FM phase region and spin splitting, making it more advantageous to realize the spin SC state. Subsequently, we prove that the FM phase becomes unstable when attractive e-h interaction is considered. As a consequence, the spin SC state can be spontaneously formed at low temperature, where spin-triplet exciton pairs act as the equivalent of Cooper pairs. We further develop a consistent BCS-type theory for the spin SC state in ABCA-stacked graphene. The predicted spin superconducting gap can reach about $7.0$ meV, with a critical temperature of about 45 K for non-doping system. At last, we demonstrated a spin-current Josephson effect in the ABCA-stacked graphene spin SC heterojunction. Our findings enrich the prospective spin SC candidate materials, illuminating more possibilities for achieving non-dissipative super-spintronics.
title	Spontaneous spin superconductor state in ABCA-stacked tetralayer graphene
topic	Mesoscale and Nanoscale Physics
url	https://arxiv.org/abs/2407.19973

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