We examine possible low-temperature phases of a repulsively Rydberg-dressed Fermi gas in a three-dimensional free space. It is shown that the collective density excitations develop a roton minimum, which is softened at a wavevector smaller than the Fermi wavevector when the particle density is above a critical value. The mean field calculation shows that unlike the insulating charge density waves states often observed in conventional condensed matters, a self-assembled metallic density wave state emerges at low temperatures. In particular, the density wave state supports a Fermi surface and a body-center-cubic crystal order at the same time with the estimated critical temperature being about one-tenth of the non-interacting Fermi energy. Our results suggest the emergency of a fermionic quantum solid that should be observable in current experimental setup.Introduction: It is well known that the system of repulsively interacting Fermi gases is mainly controlled by the celebrated Fermi liquid (FL) theory [1]. The breakdown of the FL theory can lead to exotic self-organizing orders even without the presence of lattice potentials. For example, in the strong interaction regime, the ground state may become unstable to a nematic state by breaking the rotational symmetry via a Fermi surface distortion (Pomeranchuk instability, PI [2]). For systems of a long-ranged Coulomb/dipolar interaction, it is known that particles can be "frozen" locally without exchanging their positions and form a classical crystal with one particle per site in the dilute/dense limit [3][4][5]. In another extreme situations, such as high density 3 He under pressure, the ground state can be even turned from the Fermi liquid into a quantum solid [6,7], where particles self-assemble crystal order but are still intrinsically restless and exchanging their positions even at the absolute zero of temperature.However, in the traditional condensed matter systems, these interesting phases (nematic state, classical crystal, or quantum solid) cannot be achievable easily because the interaction strength has to be strong enough to compete with the Fermi energy. On the other hand, in the system of Rydberg atoms, the length scale and strength of the effective inter-atom interaction can be manipulated easily by external fields [8][9][10][11][12]. In addition to the blockade effect for on-resonant excitations [13][14][15][16], one can also apply a far-detuned weak field (see Fig1 (a)) to generate an effective Rydberg-dressed interaction (RDI), which replaces the short-ranged Lennard-Jones potential by a soft core with finite interaction range (see in Fig1(b)) [17][18][19]. Theoretical calculations show that a repulsive RDI in a Bose gas may lead to a supersolid droplet phase [18][19][20][21][22], while an attractive RDI induces a 3D bright soliton [23]. For a Rydberg Fermi gas, some topological phases are also predicted for an attractive [24] or repulsive interaction in a optical lattice near half-filling [25].In this paper, we demonstrate that a self-assembled meta...
This work investigates the feasibility of electrical valley filtering for holes in transition metal dichalcogenides. We look specifically into the scheme that utilizes a potential barrier to produce valleydependent tunneling rates, and perform the study with both a kp based analytic method and a recursive Green's function based numerical method. The study yields the transmission coefficient as a function of incident energy and transverse wave vector, for holes going through lateral quantum barriers oriented in either armchair or zigzag directions, in both homogeneous and heterogeneous systems. The main findings are the following: 1) the tunneling current valley polarization increases with increasing barrier width or height, 2) both the valley-orbit interaction and band structure warping contribute to valley-dependent tunneling, with the former contribution being manifest in structures with asymmetric potential barriers, and the latter being orientation-dependent and reaching maximum for transmission in the armchair direction, and 3) for transmission ~ 0.1, a tunneling current valley polarization of the order of 10% can be achieved.
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