arXiv subjects

Rong Shan

Publications and source records attributed to Rong Shan.

24 records · Page 2Linked to original sources

arXiv2024

Large Language Models Make Sample-Efficient Recommender Systems

Large language models (LLMs) have achieved remarkable progress in the field of natural language processing (NLP), demonstrating remarkable abilities in producing text that resembles human language for various tasks. This opens up new opportunities for employing them in recommender systems (RSs). In this paper, we specifically examine the sample efficiency of LLM-enhanced recommender systems, which pertains to the model's capacity to attain superior performance with a limited quantity of training data. Conventional recommendation models (CRMs) often need a large amount of training data because of the sparsity of features and interactions. Hence, we propose and verify our core viewpoint: Large Language Models Make Sample-Efficient Recommender Systems. We propose a simple yet effective framework (i.e., Laser) to validate the viewpoint from two aspects: (1) LLMs themselves are sample-efficient recommenders; and (2) LLMs, as feature generators and encoders, make CRMs more sample-efficient. Extensive experiments on two public datasets show that Laser requires only a small fraction of training samples to match or even surpass CRMs that are trained on the entire training set, demonstrating superior sample efficiency.

cs.IR↗

arXiv2015

Redefinition of spin Hall magnetoresistance

Using a multi-conduction-channel model, we redefined the micromechanism of spin Hall magnetoresistance (SMR). Four conduction channels are created by spin accumulation of nonpolarized electron flow at top, bottom, left and right interfaces of the film sample, which corresponds to different resistance states of polarized electron flow with various spin directions relative to the applied magnetic field ($\mathbf{H}$), and brings about the SMR effect finally. The magnetic insulator layer, such as yttrium iron garnet (YIG), is not a requisite for the observation of SMR. Instead, the SMR effect is perfectly realized, with an order of magnitude increase, in the sample with a discontinuous layer of isolated-Co$_2$FeAl (0.3 nm) grains covered by 2.5-nm-thick Pt layer on MgO substrate. The model intuitively gives the typical relationship of SMR effect, i.e. $ρ_{\parallel}\approxρ_{\bot}>ρ_{T}$, where $ρ_{\bot}$, $ρ_{\parallel}$ and $ρ_{T}$ are longitudinal reisitivities with applied magnetic field ($\mathbf{H}$) direction perpendicular to the current direction out of plane (as Z direction), parallel with and perpendicular to it in plane (as X and Y direction), respectively. Our research reveals that the scattering between polarized and nonpolarized conduction electrons is the origin of SMR, and the intrinsic SMR is not constant when $\mathbf{H}$ direction rotates in XZ plane, which is distinct from that in the reported SMR mechanism.

cond-mat.mtrl-sci↗

arXiv2013

Proximity effect of spin orbit coupling in Pt/Co2FeAl and Pt/Permalloy bilayers_810571

Proximity effect of spin orbit coupling is investigated through anomalous Hall effect in Pt/Co2FeAl and Pt/Permalloy bilayers. A series of nontrivial magnetotransport behaviors, resulting from a strong impact of phonons on skew scattering, is observed in these films with ultrathin ferromagnetic layers. The parameters representing skew scattering, side jump and intrinsic contributions are dramatically enhanced when the ferromagnetic layer is very thin, and they have clear linear dependences on the reciprocal of ferromagnetic layer thickness, indicating a powerful influence of Pt/Ferromagnet interface. Further study on Cu/Co2FeAl and Ta/Co2FeAl bilayers reveals that a simple interface scattering without intense spin orbit coupling is not sufficient to trigger such a phenomenon. The proximity effect of spin orbit coupling is thus suggested to occur at the Pt/Ferromagnet interface, and as a result quite large anomalous Hall angle (0.036) and Nernst angle (0.23) are confirmed in the Pt/CFA films at room temperature.

cond-mat.mtrl-sci↗

arXiv2012

Fabrication and characterization of semiconducting half Heusler YPtSb thin films

The semiconducting half Heusler compound YPtSb was predicted theoretically to be capable of changing into topological insulator under proper strain. In this work, p type semiconducting half-Heusler YPtSb thin films were prepared by magnetron co-sputtering method from a specially designed target for the first time. Textured structure with (111) plane paralleling with (001) of MgO substrate was observed when YPtSb thin films were grown on MgO (100) substrate at 600°C.Electrical measurements show that the resistivity of YPtSb films decreases with increasing temperature, indicating a semiconductor-like behavior. The carrier density is as high as 1.15 X 10^21 cm-3 at 300 K. The band gap of YPtSb thin films obtained by infrared spectroscopy is around 0.1 - 0.15 eV, which is well in agreement with the theoretical prediction and the value measured in bulk YPtSb.

cond-mat.mtrl-sci↗

arXiv2012

A p-type Heusler compound: Growth, structure, and properties of epitaxial thin NiYBi films on MgO(100)

Epitaxial semiconducting NiYBi thin films were directly prepared on MgO(100) substrates by magnetron sputtering. The intensity ratio of the (200) and (400) diffraction peaks, I(200)/I(400) = 2.93, was close to the theoretical value (3.03). The electronic structure of NiYBi was calculated using WIEN2k and a narrow indirect band gap of width 210 meV was found. The valence band spectra of the films obtained by linear dichroism in hard X-ray photoelectron spectroscopy exhibit clear structures that are in good agreement with the calculated band structure of NiYBi.

cond-mat.mtrl-sci↗

arXiv2012

Electronic and crystalline structures of zero band-gap PdLuBi thin films grown epitaxially on MgO(100)

Thin films of the proposed topological insulator PdLuBi - a Heusler compound with the C1b structure - were prepared on Ta-Mo-buffered MgO(100) substrates by co-sputtering from PdBi2 and Lu targets. Epitaxial growth of high-quality PdLuBi films was confirmed by X-ray spectrometry and reflection high-energy electron diffraction. The root-mean-square roughness of the films was as low as 1.45 nm, although the films were deposited at high temperature. The film composition is close to the ideal stoichiometric ratio. The valence band spectra of the PdLuBi films, observed by hard X-ray photoelectron spectroscopy, correspond perfectly to the ab-initio-calculated density of states.

cond-mat.mtrl-sci↗