Introducing quantum confinement has uncovered a rich set of interesting quantum phenomena and allows one to directly probe the physics of confined (quasi-)particles. In most experiments, however, an electrostatic potential is the only available method to generate quantum dots in a continuous system to confine (quasi-)particles. Here we demonstrate experimentally that inhomogeneous pseudomagnetic fields in strained graphene can introduce exotic quantum confinement of massless Dirac fermions. The pseudomagnetic fields have opposite directions in the two distinct valleys of graphene. By adding and tuning real magnetic fields, the total effective magnetic fields in the two valleys are imbalanced. By that we realized valley-contrasting spatial confinement, which lifts the valley degeneracy and results in field-tunable valley-polarized confined states in graphene. Our results provide a new avenue to manipulate the valley degree of freedom.

中文翻译：

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石墨烯中的磁场可调谷对比伪磁约束

引入量子约束揭示了一组丰富有趣的量子现象，并允许人们直接探索受限（准）粒子的物理特性。然而，在大多数实验中，静电势是在连续系统中生成量子点以限制（准）粒子的唯一可用方法。在这里，我们通过实验证明应变石墨烯中的不均匀赝磁场可以引入无质量狄拉克费米子的奇异量子限制。赝磁场在石墨烯的两个不同谷中具有相反的方向。通过添加和调整真实磁场，两个谷中的总有效磁场是不平衡的。这样我们就实现了对比山谷的空间限制，这提升了谷简并并导致石墨烯中的场可调谐谷极化受限状态。我们的结果为操纵山谷自由度提供了一条新途径。