Quasiparticle origin of dynamical quantum phase transitions

Considering nonintegrable quantum Ising chains with exponentially decaying interactions, we present matrix product state results that establish a connection between low-energy quasiparticle excitations and the kind of nonanalyticities in the Loschmidt return rate. When domain walls in the spectrum of the quench Hamiltonian are energetically favored to be bound rather than freely propagating, anomalous cusps appear in the return rate regardless of the initial state. In the nearest-neighbor limit, domain walls are always freely propagating, and anomalous cusps never appear. As a consequence, our work illustrates that models in the same equilibrium universality class can still exhibit fundamentally distinct out-of-equilibrium criticality. Our results are accessible to current ultracold-atom and ion-trap experiments.Comment: 9 pages, 8 figures, accepted versio

Spin injection across magnetic/non-magnetic interfaces with finite magnetic layers

We have reconsidered the problem of spin injection across ferromagnet/non-magnetic-semiconductor (FM/NMS) and dilute-magnetic-semiconductor/non-magnetic-semiconductor interfaces, for structures with \textit{finite} magnetic layers (FM or DMS). By using appropriate physical boundary conditions, we find expressions for the resistances of these structures which are in general different from previous results in the literature. When the magnetoresistance of the contacts is negligible, we find that the spin-accumulation effect alone cannot account for the $d$ dependence observed in recent magnetoresistance data. In a limited parameter range, our formulas predict a strong $d$ dependence arising from the magnetic contacts in systems where their magnetoresistances are sizable.Comment: 6 pages, 3 eps figs. (extended version- new title + two new figures added

ANALISIS KESULITAN MENYELESAIKAN SOAL LINGKARAN PADA SISWA KELAS VIII MTs AL KHAIRAAT AMBON

Penelitian ini bertujuan untuk mendeskripsi kesulitan yang dialami siswa kelas VIII MTs AlKhairaat Ambon yang berkaitan dengan fakta, konsep, skill, dan prinsip dan faktor yang menyebabkan kesulitan dalam menyelesaikan soal lingkaran. Tipe penelitian ini adalah penelitian kualitatif. Subjek dalam penelitian ini adalah 3 orang siswa kelas VIII MTs Al Khairaat Ambon yang memperoleh nilai terendah berdasarkan hasil tes awal untuk materi teorema phytagoras dan lingkaran yang diikuti 14 siswa. Pengumpulan data dilakukan melalui Tes, wawancara dan dokumentasi. Analisis data yang digunakan terdiri dari reduksi data, penyajian data, kesimpulan, pemeriksaan atau pengecekkan keabsahan data. Hasil penelitian menunjukan bahwa siswa mengalami kesulitan fakta, konsep, skill dan prinsip. Adapun faktor yang menyebabkan siswa mengalami kesulitan dalam menyelesaikan soal lingkaran adalah sering miskonsepsi atau mengalami kesalahan konsep dalam penyelesian soal matematika, kurang pemahaman dan tidak teliti dalam menyelesaikan soal lingkara